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Using precision tools to manage and evaluate the effects of mineral and protein/energy supplements fed to grazing beef heifers

Using precision tools to manage and evaluate the effects of mineral and protein/energy... Translational Animal Science, 2023, 7, 1–11 https://doi.org/10.1093/tas/txad013 Advance access publication 28 January 2023 Technology in Animal Science Using precision tools to manage and evaluate the effects of mineral and protein/energy supplements fed to grazing beef heifers †,1 † |‡ †,2, Kacie L. McCarthy, Sarah R. Underdahl, Michael Undi, and Carl R. Dahlen Center for Nutrition and Pregnancy and Department of Animal Sciences, North Dakota State University, Fargo, ND, USA |‡ Central Grasslands Research Extension Center, North Dakota State University, Streeter, ND, USA Present address: Department of Animal Science, University of Nebraska, Lincoln, NE 68583, USA Corresponding author: carl.dahlen@ndsu.edu ABSTRACT Our objectives were to develop a Mobile Cow Command Center (MCCC) capable of precision monitoring of grazing heifers to 1) examine the relationship between supplement intake on concentrations of liver mineral and blood metabolites and 2) examine activity, reproductive, and health behavior. Yearling crossbred Angus heifers (N = 60; initial BW = 400.4 ± 6.2 kg) were fitted with radio frequency identification ear tags that allowed access to electronic feeders (SmartFeed system; C-Lock Inc., Rapid City, SD), and with activity monitoring tags (CowManager B.V., the Netherlands) that monitored reproductive, feeding, and health-associated behaviors. Heifers were assigned randomly to one of three treatments for a 57-day monitoring period: 1) no supplement (CON; N = 20), 2) free choice mineral (MIN; Purina Wind and Rain Storm [Land O’Lakes, Inc.], N = 20), or 3) free choice energy and mineral supplement (NRG; Purina Accuration Range Supplement 33 with added MIN [Land O’Lakes, Inc.], N = 20). Consecutive day body weights, blood, and liver biopsies were collected at pasture turnout and final day of monitoring. By design, mineral intake was greatest in MIN heifers (49 ± 37 g/d) and energy supplement intake was greatest in NRG heifers (1,257 ± 37 g/d). Final BW and ADG were similar among treatments (P > 0.42). Concentrations of glucose on day 57 were greater (P = 0.01) in NRG compared with CON and MIN heifers. Liver concentrations of Se and Fe on day 57 were greater (P < 0.05) in NRG heifers than CON, with MIN being intermediate. Activity tags reported NRG heifers spent less time eating (P < 0.0001) and more time (P < 0.0001) being “highly active” than MIN with CON heifers being intermediate. Data retrieved from activity tags identified 16 of 28 pregnant heifers exhibiting some type of estrus-associated behavior even after confirmation of established pregnancy. The activity monitoring system triggered a total of 146 health alerts from 34 of the 60 heifers monitored, but only 3 heifers of the heifers initiating an electronic health alert needed clinical treatment. However, animal care staff identified nine additional heifers that required treatment for which no electronic health alert was generated. The electronic feeders successfully controlled intake of indi- vidual heifers managed in groups pastures; however, the activity monitoring system misrepresented estrus and health events. Key words: activity monitoring, beef cattle, electronic feeder, mineral, supplement, grazing INTRODUCTION and to offset forage nutritive decline throughout the grazing season (Schauer et al., 2004; Cline et al., 2009; McCarthy et Technology continues to improve and some sectors of agri- al., 2021). An issue observed with providing supplements on culture are rapidly implementing new innovations into di- pasture is the large variability in consumption by individuals verse applications. The beef industry, however, is slower than within a group (Tait and Fisher, 1996; Bowman and Sowell, other agricultural industries in rate of adoption (Dahlen et al., 1997; Cockwill et al., 2000; Patterson et al., 2013), which 2014; Lamb et al., 2016). Several reasons likely exist for this is largely unseen and unknown by cattle management per- adoption lag, foremost of which are the lack of comprehen- sonnel. In addition, frequent observation of activity and re- sive technological solutions that can be implemented in ex- productive behavior of grazing cattle is often difficult due to pansive pasture settings, and the lack of solutions from which the expansive nature of pastures and being labor intensive management decisions can be made over the life of an animal. (Elischer et al., 2013). Electronic systems that can monitor Individual animals within a herd of cattle are unique, are in feeding, physical activity, and reproductive-related behavior varying stages of production, have specific nutritional needs, are now available. and present differing health statuses. Within the herd, indi- Activities reported in this study are aimed at developing vidual animal variation exists and changes throughout the a system (the Mobile Cow Command Center) that pairs production year, presenting real and relevant management is- multiple technologies into a single portable unit that would sues for progressive producers. allow for precision management of individuals within a herd Producers often provide mineral and/or protein and energy on expansive pastures to optimize production efficiency, supplements to grazing cattle to maintain targeted produc- improve animal health, and enhance profitability. Our tion goals for growth and reproductive performance (Schillo objectives were to develop a Mobile Cow Command Center et al., 1992; Ciccioli et al., 2005; Cappellozza et al., 2014) (MCCC) for monitoring heifers on native range specifically Received December 13, 2022 Accepted January 25, 2023. © The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. 2 McCarthy et al. to 1) examine the relationship between mineral and energy Training Period supplementation on intake, liver mineral concentrations, Two heifer development pens (N = 63 per pen) were utilized and metabolites and 2) examine activity, reproductive, and at the CGREC for a 2-week training period where one MCCC health behavior. unit was placed in each dry lot pen. A portion of the heifer development ration (corn silage) was placed into the feed bins and heifer intake was monitored. Only heifers with a history MATERIALS AND METHODS of feed consumption from the feeders were selected as exper- All animal procedures were approved by the Institutional imental units for this experiment. Animal Care and Use Committee at North Dakota State University (A18069). Heifer Selection All heifers were estrus synchronized using a controlled in- Study Area ternal drug release (CIDR; Zoetis, Parsippany, NJ) protocol Research was conducted at the Central Grasslands Research (7 d CO-Synch plus CIDR), with heifers receiving 2  mL in- Extension Center (CGREC), located near Streeter, ND from tramuscularly GnRH (Factrel; Zoetis, Parsippany, NJ) and July 25 to September 19. This area is characterized by a con- CIDR insert on day 0. Seven days later, the CIDR insert was tinental climate with warm summers and cold winters with a removed and a single injection of PGF (5  mL intramuscu- 2α majority (72%) of precipitation occurring between May and larly; Lutalyse; Zoetis, Parsippany, NJ) were administered September (Limb et al., 2018). August is the warmest month followed by GnRH and artificial insemination (AI), approxi- with a mean temperature of 18.6°C (NDAWN, 2017). mately 60 h later. All heifers received an estrus detection patch The pasture was 70 ha with a stocking rate of 1.99 Animal (Estrotect; Rockway Inc., Spring Valley, WI) to monitor estrus Unit Months (AUMs)/ha. The vegetation is classified as mixed- (Hill et al., 2014). On the day of AI, final heifer selection for grass prairie dominated by western wheatgrass (Pascopyrum the experiment was made based on 1) history of consuming smithii [Rydb.] À. Löve), green needlegrass (Nassella viridula feed from SmartFeed feeders and 2) activated estrus detection [Trin.] Barkworth) and blue grama (Bouteloua graciles [Willd. patches. A total of 60 of the 126 heifers met the criteria for ex Kunth] Lag. ex Griffiths). Other important species include inclusion in the experiment and were bred using sexed semen sedges (Carex spp.), prairie junegrass (Koeleria macrantha (Tehama Tahoe B767 14AN502) for female offspring. [Ledeb.] Schult.), sages (Artemisia spp.), goldenrods (Solidago spp.), kentucky bluegrass (Poa pratensis L.) a nonnative grass Grazing Period and western snowberry (Symphoricarpos occidentalis Hook.) a native shrub (Limb et al., 2018). Sixty crossbred yearling Angus heifers (initial BW = 400  ±  6  kg) were managed as a single pasture group with Mobile Cow Command Center Units free access to graze native range and were randomly assigned Each of two Mobile Cow Command Center (MCCC) units to 1 of 3 dietary treatments 1) no access to feed supplements were developed by pairing two commercially available (CON; N = 20), 2) free choice access to mineral supplement technologies into single trailer units that can be transported (MIN; Purina Wind & Rain Storm All-Season 7.5 Complete, and function anywhere cattle are managed. The first tech- Land O’Lakes, Inc., Arden Hills, MN, N = 20), or 3) free nology is the SmartFeed device (C-lock Inc., Rapid City, SD), choice access to energy supplement (NRG; Purina Accuration which is a self-contained system designed to measure supple- Range Supplement 33, Land O’Lakes, Inc., Arden Hills, MN, ment intake and feeding behavior from individual cattle in N = 20). The manufacturer recommendation for daily intake group settings. The system is solar powered and includes a of the mineral supplement was 113 g. The NRG supplement radio-frequency identification (RFID) reader, weigh scales, was formulated by adding 68.1 kg MIN to a 907.4 kg mix- access control gate, a feed bin, and a cloud-based interface ture of 60% ground corn and 40% Accuration (25.5 % CP; which continuously logs feed intake and feeding behavior Table 1) with an anticipated daily intake of 1.63  kg. Thus, data. The programming of the SmartFeed units is flexible, if heifers in the NRG treatment consumed 1.63  kg of sup- with the ability to assign specific animals to specific feeders plement, and heifers in the MIN treatment consumed 113 g, and to prohibit entry of individual animals once a daily target then both the MIN and NRG heifers would be consuming intake is achieved. The second technology included in the the same amount of the mineral product used. The MIN MCCC was the CowManager system (CowManager B.V., the and NRG supplements were delivered via the MCCC units Netherlands), which fits over an RFID ear tag and uses ad- which were located within 50 m of the waterer in the pasture. ditional sensors to monitor cow reproductive (estrus alerts), Feeders were set to restrict access of CON heifers from either feeding-related (eating, rumination, and activity level), and trailer unit, with MIN and NRG heifers having ad libitum ac- health-associated data. The CowManager ear tag continu- cess to the trailer containing their respective feed assignment. ously registers movements from the cow’s ear and classifies Because few heifers consumed either supplement early in the the data through proprietary algorithms (Pereira et al., 2018). grazing season (Figure 1), feed intake data were summarized Data are sent through a wireless connection, via a router over a 57-d period; from the time of pregnancy diagnosis placed on the top of the MCCC unit. Data are then received (July 25) until removal from pasture (September 19). through a coordinator unit that is attached to a computer in a The CowManager system reported the minutes spent lab (approximately 200 m line of site from the MCCC units) during each hour of every day in activity categories in- that automatically uploaded the data for viewing on any de- cluding “eating”, “ruminating”, “not active”, “active”, vice with an internet connection. Each MCCC contained 2 and “highly active”, with a proprietary model and avail- SmartFeed units, controlling hardware and the CowManager able through the web-based application. Estrus-related router in an enclosed trailer with open feed access areas and alerts were continuously generated via the CowManager retractable wheels for transport. system, including classifications of “in heat”, “potential”, or Precision management of beef heifers 3 Table 1. Dietary ingredient and nutrient composition of mineral (MIN) and were dried in a forced-air oven at 60°C for at least 48 h and energy with mineral (NRG) supplement fed to grazing beef heifers then ground to pass through a 2-mm screen using a Wiley mill (Arthur H. Thomas, Philadelphia, PA). Clipped forage % DM basis samples for each location reported herein were composite 1 2 Nutrient analysis NRG MIN over all locations within the representative sampling date and reported as averages within month. Forage samples were DM 94.95 — analyzed at the North Dakota State University Nutrition Ash 12.69 — Laboratory for dry matter (DM), ash, N (Kjehldahl method), CP 25.49 — Ca, P, and ether extract (EE) by standard procedures (AOAC, N 4.08 — 1990). Crude protein (CP) was calculated by multiplying N NDF 15.77 — by 6.25. Neutral detergent fiber (NDF) and acid detergent ADF 5.78 — fiber (ADF) concentrations were determined by the modi- Ether extract 6.17 — fied method of Van Soest et al. (1991) using a fiber analyzer Mineral analysis, mg/kg (Ankom Technology Corp., Fairport, NY). Samples were also analyzed for Cu, Zn, Co, Mo, Fe, S, and Se using inductively Ca 18,499 176,939 coupled plasma optical emission spectroscopy (ICP-OES) P 10,047 76,274 by the Veterinary Diagnostic Laboratory at Michigan State S 7,150 8,165 University. Se <100.0 <100.0 Fe 462 6,628 Liver Sample Collection and Analysis Cu 1,079 796.3 Because the liver is a major organ of mineral storage and Zn 429.9 2,590.5 concentrations of minerals in the liver are indicative of min- Mo 8.6 15.7 eral status in ruminants (Spears et al., 2022), liver samples were collected at pasture turnout and at the final day of Mn 202.6 2,860.4 monitoring via biopsy from a subset of heifers from each re- Co 67.14 10.35 spective treatment (N = 24, 8 per treatment). Liver biopsy samples (approximately 20 mg) were collected as previously NRG = Purina Accuration Range Supplement 33 with added MIN (Purina Wind & Rain Storm All-Season 7.5 Complete; Land O’Lakes, Inc., Arden described by McCarthy et al. (2020). Liver samples frozen Hills, MN). Formulated by adding 68.1 kg MIN to a 907.4 kg mixture of at −20°C, then sent on ice to the Veterinary Diagnostic 60% ground corn and 40% Accuration. MIN = Purina Wind & Rain Storm All-Season 7.5 Complete (Land Laboratory at Michigan State University and were evaluated O’Lakes, Inc., Arden Hills, MN). Ingredients: Dicalcium Phosphate, for concentrations of minerals using inductively coupled Monocalcium Phosphate, Calcium Carbonate, Salt, Processed Grain plasma mass spectrometry (ICP-MS). ByProducts, Vegetable Fat, Plant Protein Products, Potassium Chloride, Magnesium Oxide, Vitamin E Supplement, Vitamin A Supplement, Natural and Artificial Flavors, Calcium Lignin Sulfonate, Ethoxyquin Blood Collection and Serum Analysis (a Preservative), Manganese Sulfate, Vitamin D3 Supplement, Zinc Blood metabolites were analyzed from a subset of heifers Sulfate, Basic Copper Chloride, Ethylenediamine Dihydroiodide, Cobalt Carbonate. The vitamin was labeled to contain 136,054, 13,605, and 136 from each respective treatment (N = 30). Blood samples were IU/kg of Vitamins A, D, and E, respectively. 3 collected at pasture turnout and at the final day of monitoring Analysis for concentrations of trace minerals was done using an ICP-OES panel for premix evaluation with the lowest detection limit for Se of via jugular venipuncture into serum tubes (10  mL; Becton 100 mg/kg. Company guaranteed analysis for concentrations of Se in MIN Dickinson Co., Franklin Lakes, NJ), allowed to clot for supplement was 27 mg/kg. 30  min and centrifuged at 1,500 × g at 4°C for 20  min. Serum was separated and stored in plastic vials at −20°C “suspicious”. Pregnancy detection was performed 34 d after until further analysis. Serum samples were analyzed for glu- AI via transrectal ultrasonography (7.0-MHz transducer, 500 cose and NEFA. Samples were analyzed using the Synergy H1 V Aloka, Wallingford, CT). Continuous monitoring with Microplate Reader (Biotek, Winooski, VT) with the Infinity the CowManager tag provided data related to heifer estrus Glucose Hexokinase Kit (Thermo Scientific, Waltham, MA) activity. A retrospective analysis was conducted to deter- and NEFA-C Kit (WAKO Chemicals, Inc., Richmond, VA). mine the accuracy of estrus-related alerts generated via the The intra- and interassay CV was 2.62% and 3.41%, for CowManager system versus a known pregnancy status de- serum glucose, respectively and 7.75% and 8.29%, for serum termined via ultrasound. Similarly, a retrospective analysis NEFA, respectively. was conducted to evaluate the accuracy of health events that Statistical Analysis were flagged via the CowManager system (reported as “sick”, “very sick”, or “no movement”) by comparing electronic Heifers assigned to MIN and NRG treatments that did not alerts with treatment logs generated by the animal care staff. voluntarily consume their assigned supplements from the It is important to note that the CowManager system has been electronic feeders were retrospectively added to CON treat- validated using the proprietary algorithm in populations of ment for analysis, resulting in a final N of 29 CON, 18 MIN dairy cows housed indoors (Bikker et al., 2014) and grazing ,and 13 NRG heifers, respectively. Data were analyzed as a (Pereira et al., 2018). completely randomized design with heifer used as the ex- perimental unit for all analysis. Performance and intake Forage Collection and Analysis data were analyzed using the GLM procedure of SAS (9.4, Forage samples were obtained every 2 weeks from 20 dif- SAS Inst. Inc., Cary, NC) with treatment as the fixed effect. ferent locations in the pasture in a diagonal line across the Blood metabolites were also analyzed using the GLM pro- pasture. The forage samples were hand clipped to a height cedure and the model statement used contained the effects of 3.75 cm above ground (Undi et al., 2008). Forage samples of treatment and baseline serum metabolite concentrations 4 McCarthy et al. Figure 1. Daily intake of mineral (MIN) or energy with mineral (NRG) supplements of heifers grazing native range over the duration of the grazing season. The 57-d monitoring period was initiated from the time of pregnancy diagnosis (July 25th) until removal from pasture (September 19th). Treatments include: MIN (N = 18), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 13), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. at pasture turnout. Concentrations of mineral in liver attended feeders compared with MIN (2.1 ± 0.6 min/d) and samples were analyzed using the GLM procedure and the CON heifers (1.3  ±  0.6  min/d). Additionally, NRG heifers model statement used contained the effect of treatment, with visited the feeders more (P < 0.001) times (9.20  ±  0.34 values from baseline pasture turnout liver samples used as times/d) on days they attended feeders compared with MIN a covariate. Total mineral intake from supplemental sourced (2.71 ± 0.34 times/d) and CON heifers (1.94 ± 0.34 times/d). was calculated by multiplying total supplement intake over Over the 57-day monitoring period, heifers in the MIN the 57-day monitoring period by the analyzed concentration treatment consumed 49.3  ±  37  g/d of mineral supplement. of the respective supplement (MIN or NRG) consumed by Heifers in the NRG treatment consumed 1,257.1 ± 37 g/d of individual heifers. Total mineral intake data were analyzed energy supplement. Mean values for NRG supplement intake using the GLM procedure of SAS with a model including by heifers in the CON treatment were driven by 3 heifers that treatment. Data for activities including daily time spent consumed a total of 63.3 g/d over the monitoring period at eating, ruminating, not active, active, and highly active were the NRG supplement feeder. Mean values for MIN supple- analyzed using the MIXED procedure of SAS for repeated ment intake by heifers in the CON treatment were driven by measures in time with treatment, day, and their interaction in 26 feeding attempts where 2.8  g/d of MIN supplement was the model. Results are reported as least square means using consumed during 7.7 of the 57 d (13% attendance) during the the LSMEANS statement for liver and plasma. For all anal- monitoring period. Over the monitoring period, NRG heifers ysis, significance was set at P ≤ 0.05. spent more (P < 0.001) time (2.9 ± 0.34 min/d) at the feeder compared with MIN (0.72  ±  0.34  min/d) and CON heifers (0.18  ±  0.34  min/d). Additionally, during the monitoring period, NRG heifers visited the feeders more (P < 0.001) times RESULTS AND DISCUSSION daily (6.18 ± 0.15 times/d) than MIN (2.71 ± 0.15 times/d) Heifer Intake, Feeding Behavior, and Performance and CON heifers (0.25 ± 0.15 times/d). Intake of energy and mineral supplements were minimal Certainly, heifers not assigned to the respective treatments during the early portion of the grazing season but began to did attempt to consume supplement. However, the SmartFeed increase in midAugust as the quality of native range declined system was able to limit the frequency of feeder attendance (Figure 1). Proportion of days attending feeders was greater and supplement consumption by heifers that were not desig- (P < 0.001) for NRG heifers (68  ±  2.04%) compared with nated to consume the respective supplements via that online MIN heifers (41  ±  2.04%). Overall number of days heifers control system. Cows that were being fed in SmartFeed units were present at the NRG and MIN feeders was 38.7 and (McCarthy et al., 2021) consumed more mineral supplement 23.1  ±  1.2 d of the 57 d, respectively. More supplement (P on average (125.4 g/d) than heifers reported herein. In com- < 0.001) was consumed on days that NRG heifers attended parison, Smith et al. (2016) built a custom mineral feeder with feeders (1,877 ± 76 g/d of energy supplement) compared with an RFID reader and reported that steers that had access to a days when MIN heifers attended feeders (122  ±  76  g/d of commercially available free-choice mineral consumed 72 g/d mineral supplement). Energy supplement heifers spent more per head over a 90-d grazing period. The mineral disappear- (P = 0.01) time at the feeders (4.1 ± 0.6 min/d) on days they ance in Smith et al. (2016) was within a range of manufacturer Precision management of beef heifers 5 recommended intakes of 40 to 125 g/head per day. Moreover, ADG (0.75 kg/d) over a 19-day feeding period (Cappellozza researchers in Oklahoma (Reuter et al., 2017) conducted a et al., 2014a). Heifers on the NRG treatment in the current pilot study using the SmartFeed system to characterize the experiment were likely substituting a portion of forage in- daily variation in soybean meal supplement with the inclu- take with the supplement consumed (Summers et al., 2015). sion of salt on intake by group-housed, self-fed grazing steers. Collectively, heifers assigned to the NRG treatment may have Fifteen steers from Reuter et al. (2017) consumed 1,210 g/d simply not consumed enough supplement over the course of of supplement with a 45% salt inclusion for a 14-d period. the experiment to compensate for reduced forage intake and Although steers consumed a similar amount of supplement elicit a subsequent gain response. compared to heifers reported herein, variation among ani- Blood Metabolites mals was also reported with animals visiting 5.1 ± 1.3 times/d over the 14-d period (Reuter et al., 2017). Over the duration Though no gain response was observed, concentrations of this study, heifers visited the feeders a similar number of of glucose in serum were 14% greater (P = 0.01) in NRG times compared with those reported by Reuter et al. (2017) heifers compared with CON and MIN heifers at the end utilizing the same feeder technologies. The variation among of the monitoring period (Table 2). Similar concentrations animals from Reuter et al. (2017) suggests that competition of glucose have been reported in beef heifers offered low- for use of one SmartFeed unit may have been a challenge starch energy supplements daily or three times weekly (76.3 because intervals between different RFID readings (animals and 70.5 mg/dL, respectively; Moriel et al., 2012) or where exchanging places at the feeder) was less than 1  s per an- heifers received either energy (provided as cracked corn, soy- imal. Heifers in the current study may have been experiencing bean meal, and urea) or protein (provided as soybean meal) similar challenges with competition at the feeder even though supplements while consuming cool-season forages (65.0 they had an additional SmartFeed unit to visit. This postulate and 65.1  mg/dL, respectively; Cappellozza et al., 2014b). was corroborated with visual observations of heifers vigor- Since starch is a major dietary precursor for glucose in ously exchanging places at the feeder when the herd did visit ruminants (Huntington, 1997), the observation of elevated the proximity of the feeders. concentrations of glucose in heifers receiving the NRG (i.e. The manufacturer label for the mineral supplement pro- starch-based) supplement was expected. Starch fermenta- vided recommended optimum intakes of 113  g/head daily. tion in the rumen results in greater propionate and less ac- Over the 57-day monitoring period, 1 in 18 (0.06%) MIN etate production, and therefore a greater supply of glucose heifers consumed recommended MIN intake, but heifers did to the animal (Huntington, 1997). Furthermore, other studies not attend feeders daily. On days they did attend the feeder 10 (Cooke et al., 2008) have reported increases in plasma glu- of the 18 (56%) heifers that attended the feeders consumed cose concentration in heifers supplemented infrequently and recommended feeding rates of MIN supplement. Variation attributed those increases to the time required for synthesis in individual consumption has been related to number and and activation of gluconeogentic enzymes to change glucose placement of feeders, individual animal preference, weather, synthesis and released by the liver. individual and herd behavior, characteristics of the feedstuff, There were no differences among treatments in and feed additives that may be included (Tait and Fisher, concentrations of NEFA in serum at the conclusion of 1996; Bowman and Sowell, 1997; Smith et al., 2016). the experiment (P = 0.85; Table 2). Circulating NEFA Overall, heifer final BW was similar among treatments concentrations reflect fat mobilized from body reserves, (433  ±  6  kg; P = 0.42). Interestingly, treatment did not in- with elevated concentrations often associated with negative fluence body weight gain (P = 0.76) during the monitoring energy balance. Nevertheless, it is important to note that period, with heifer ADG equal to 0.46  kg/d. Many studies heifers from all treatments were in a positive nutritional highlight enhanced gain in heifers consuming supplemental status based on similar ADG and, therefore, no mobilization feeds (Delcurto et al., 2000; Engel et al., 2008; Summers of body reserves was likely necessary in any treatments. As et al., 2015). However, previous studies have reported that animals experience compensatory gain, concentrations of neither trace mineral supplementation nor source (organic NEFA have been reported to rapidly decline (Ellenberger et and inorganic) affected cow BW or BCS (Olson et al., 1999; al., 1989). McFarlane et al. (2017) provided protein supple- Muehlenbein et al., 2001; Ahola et al., 2004). Similarly, preg- ment to growing heifers grazing winter forage and reported nant heifers provided an energy supplement as a mixture of no differences in concentrations of NEFA in serum, which cracked corn, soybean meal, and urea while consuming low- was not expected due to the fact that the authors observed quality cool-season forages in feedlot pens reported similar BW changes in heifers. In contrast, Cappellozza et al. (2014b) Table 2. Effects of mineral (MIN) or energy with mineral (NRG) supplements on concentrations of serum metabolites in heifers grazing native range Treatment P-value Item CON MIN NRG SEM TRT NEFA, µmol/L 327.1 326.2 291.7 47.04 0.85 b b a Glucose, mg/dL 66.7 66.5 75.9 2.12 0.01 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 10), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 8), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. Results covariately adjusted to baseline serum sample taken at pasture turnout. 6 McCarthy et al. reported that control heifers had greater concentrations of programming effects on offspring conceived and gestated in NEFA compared with heifers receiving either energy (pro- extensive pasture conditions. vided as cracked corn, soybean meal, and urea) or protein (provided as soybean meal) supplements while consuming Forage Analysis cool-season forages. Although it is important to note that Forage nutrient content appeared to decrease over the course Cappellozza et al. (2014b) reported unexpected differences of the grazing period (Table 3) observed by percentage of with control heifers, all heifers were in a positive nutritional CP decreasing and greater NDF values over the season. As status. Therefore, lack of differences among treatments re- forage nutritive value decreased, we observed increases in ported herein was likely due to heifers not being in negative supplement intakes (Figure 1). A decrease in the forage nu- energy balance through the grazing period. tritive value is typical in diets of grazing cattle during the It is important to note that during the time of supple- advancing season (Bedell, 1971; Johnson et al., 1998; Cline mentation in the current study, heifers were in early stages et al., 2009; McCarthy et al., 2021). Typically, the nutrient of gestation. The maternal gastrointestinal tract is critical availability of grazed forages fluctuates by environmental for nutrient acquisition and is a major nutrient sink during conditions, forage species, soil type and stage of maturity pregnancy (Vonnahme et al., 2015) and the relationship be- (NASEM, 2016). tween maternal nutrient intake during pregnancy and fetal For beef breeding cattle, recommended allowances for growth are extremely important (Redmer et al., 2004; Dahlen Se, Fe, Cu, Zn and Mn are 0.10, 50, 10, 30 and 40 mg/kg et al., 2021; Reynolds et al., 2022). Research from Perry et al. of diet, respectively (NASEM, 2016). Iron in pastures has (1999) determined that low dietary protein (provided as cot- been shown to have seasonal fluctuations with peaks in tonseed meal) in the first trimester of pregnancy followed by spring and autumn (Suttle, 2010), where our current forage increased protein in the second trimester may have an effect Fe concentrations are greater over the course of the grazing on placental development and thus subsequent impacts on season. According to Corah and Dargatz (1996), forage Fe calf body weight in primiparous heifers. In addition, a similar is within adequate levels at 50 to 200 mg/kg. Most forage mineral and protein/energy supplements fed to beef heifers contains 70 to 500  mg Fe/kg (NASEM, 2016), which the during early gestation resulted in altered fetal liver and femur current pasture falls within the range. Concentrations of weights, concentrations of mineral in fetal liver and muscle, Cu in forage were marginal to deficient (4 to 7 vs. < 4 mg/ concentrations of amino acids in the amniotic fluid, and al- kg, respectively; Corah and Dargatz, 1996). Forages vary tered placental gene expression by day 83 of gestation (Diniz in Cu content, with legumes usually having higher content et al., 2021; Menezes et al., 2021; McCarthy et al., 2022; than grasses (NASEM, 2016). Moreover, concentrations of Menezes et al., 2022). Therefore, observations of altered Zn were deficient (<20  mg/kg) until midAugust to early metabolite and mineral profiles as observed in the current September. According to Corah and Dargatz (1996), Mo, experiment may be impacting the developing fetus, and fur- Co, and Mn were adequate (<1, 0.1 to 0.25, and >40 mg/ ther investigation is warranted to determine the potential of kg, respectively). As stated by Suttle (2010), Mn values for using electronic feeding equipment to impose developmental pastures vary, with a mean value of 86 mg/kg. In addition, Table 3. Forage analysis of representative sample composites of pasture grazed by beef heifers provided either mineral (MIN) or energy with mineral (NRG) supplement from June to September Grazing period Item June July August September TDN 60.5 62.0 60.6 58.6 CP, % 9.02 7.1 6.8 5.9 Ash 10.04 9.4 10.3 10.5 NDF, % 62.87 59.1 61.1 64.5 ADF, % 35.9 34.1 35.9 38.4 Ca, % 0.21 0.33 0.41 0.42 P, % 0.40 0.14 0.12 0.10 S, % 0.1416 0.1498 0.1616 0.1503 Se, mg/kg <10.0 <10.0 <10.0 <10.0 Fe, mg/kg <50 101 130 166 Cu, mg/kg 4.6 4.1 4.5 3.8 Zn, mg/kg 14.8 17.7 20.0 23.7 Mo, mg/kg 1.4 1.4 1.7 1.3 Mn, mg/kg 59 60.7 84.0 100.4 Co, mg/kg <1.00 <1.00 <1.00 <1.00 Clipped forage samples from 20 different locations reported herein are composite over all locations within the representative sampling dates. Values presented are mean values of the representative sampling dates within the given month: June (N= 1), July (N = 3), August (N = 2), and September (N = 3). TDN = 88.9 – (0.79 × ADF%); Holland and Kezar, 1995 Precision management of beef heifers 7 Mn requirements for breeding cattle are higher than Liver Mineral Concentrations and Supplemental growing and finishing cattle due to reproduction demands Mineral Intake (NASEM, 2016). At the end of the monitoring period, concentrations of Se and Similar forage responses in the Northern Great Plains Fe in liver of NRG heifers were greater (P = 0.01; Table 4) have been reported by investigators (Johnson et al., 1998; than CON, whereas MIN were intermediate. Concentrations Cline et al., 2009) who have observed increases in forage of liver Co at the end of the monitoring period were greater fiber content with the advancing season. In addition, avail- in NRG heifers (P < 0.001) compared with MIN, which were able forage protein may decrease enough over the grazing greater (P < 0.001) than CON. Furthermore, no differences (P season that optimal livestock performance may require ≥ 0.12) were observed in concentrations of liver Cu, Zn, Mo, supplementation (Bodine et al., 2001). As noted, intakes and Mn among treatments. According to guidelines published of NRG supplement by heifers increased with advancing by Kincaid (2000), liver concentrations of Fe, Zn, Se, Mo, season. Furthermore, mineral intake is often affected by and Mn in all treatment groups were considered adequate at season of the year, with the greatest intakes often during the the end of the grazing period. Additionally, concentrations of winter or dry season when forages stop growing, become liver Co in all treatment groups were above levels considered high in fiber and lignin and low in digestibility (McDowell, to be satisfactory (0.08 to 0.12 μg/g DM; McNaught, 1948). 1996). This was also corroborated with MIN supplemented In contrast, Cu values would be considered marginal (33 heifers that started consuming more supplement later in the to 125 μg/g DM; Kincaid, 2000). The lower concentrations season. Moreover, native forages typically grazed by beef of Cu noted in CON heifers can be supported by the low cattle are generally deficient to marginal in Cu, Mn, Se, and forage value for Cu concentrations reported herein and Zn concentrations (Umoh et al., 1982); therefore, supplying therefore mineral supplementation may result in increased supplemental minerals under these grazing conditions are concentrations of Cu in heifers grazing native range. typically performed. Over the course of the grazing season, Data in the current report align with McDowell (1996) the most notable change in forage mineral concentra- who suggested that the most efficient method for providing tion were noted in decreasing concentrations of Cu, and supplemental minerals may be through a combination with increasing concentrations of Fe, Zn, and Mn. concentrates to ensure that adequate intake of minerals Table 4. Effects of mineral (MIN) or energy with mineral (NRG) supplements on liver mineral concentrations at pasture removal in heifers grazing native range Treatment P-value Item , µg/g CON MIN NRG SEM TRT b a,b a Se 1.40 1.61 1.85 0.118 0.01 b a,b a Fe 197.7 213.0 286.0 28.57 0.05 Cu 75.3 106.0 110.2 16.39 0.12 Zn 99.8 103.3 112.6 8.60 0.47 Mo 3.65 3.93 3.70 0.269 0.58 Mn 9.25 8.99 10.66 0.810 0.27 c b a Co 0.13 0.32 0.41 0.02 <0.001 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 7), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 5), free choice access to energy and mineral supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)] Results covariately adjusted to baseline liver biopsy taken at pasture turnout. Table 5. Total supplemental mineral intake in heifers consuming mineral (MIN) or energy with mineral (NRG) supplements over a 57-d period Treatment P-value Item, g CON MIN NRG SEM TRT c b a Fe 1.1 18.6 33.1 1.96 <0.0001 b b a Cu 0.5 2.2 77.3 2.69 <0.0001 c b a Zn 0.5 7.3 30.8 1.23 <0.0001 b b a Mo 0.005 0.044 0.616 0.022 <0.0001 c b a Mn 0.48 8.04 14.52 0.852 <0.0001 b b a Co 0.026 0.029 4.81 0.167 <0.0001 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 7), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 5), free choice access to energy and mineral supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. 8 McCarthy et al. along with other nutrients are consumed. This strategy can and CON heifers spent a similar amount of time being be effective in decreasing the variability in free-choice trace highly active (141.1 and 141.4  min/d, respectively), with mineral intake and bolstering tissue stores during winter NRG heifers spending 20 more minutes being highly active or when energy/protein supplements are provided. The (165.3  min/d; P < 0.0001) compared with other treatments. NRG treatment in the current experiment was formulated Heifers reported herein were moving throughout the pasture so that at a projected intake level, heifers would consume as a herd of 60 cattle, which may explain the high level of the same 113  g/head daily of the same mineral source the activity reported from the 13 NRG heifers as they competed MIN heifers were receiving. Though NRG heifers did not for supplement from the 2 feeder spaces in the MCCC units. achieve the anticipated intake, they ultimately consumed The CowManager system has been validated for rumination greater (P < 0.0001; Table 5) amounts of supplemental and activity measures in dairy cattle kept in freestalls (Bikker Fe, Cu, Zn, Mo, MN, and Co compared with MIN heifers et al., 2014), or grazing (Pereira et al., 2018), and with feedlot that just had free choice access to the mineral supplement. cattle in confinement (Wolfger et al., 2015). However, there Therefore, increased liver concentrations of Co for NRG is paucity of data related to beef cattle managed in extensive heifers compared with MIN heifers were not unexpected. grazing scenarios. Also, NRG heifers consumed 77.96% more Fe compared to The retrospective evaluation of estrus alerts generated total supplemental mineral intake in MIN heifers, therefore via the CowManager system revealed that 16 of 28 heifers corroborating the increased concentrations of Fe in the liver (57%) confirmed pregnant via ultrasound were incorrectly of NRG heifers. In addition, because a majority of NRG identified as displaying some type of estrus behavior (two consumption was late in the monitoring period, we antici- reported as in heat, 11 reported as potential, and three re- pate that if heifers were allowed to continue their respective ported as suspicious). If producers were using this tech- treatments for additional time that concentrations of other nology for estrus detection in a pasture setting, additional liver minerals would subsequently diverge between the MIN confirmation of estrus behavior would be important to and NRG heifers. consider for use in AI breeding. Additional resources such as estrus detection patches to determine heat state (Hill Activity Monitoring T ags et al., 2014) or visual observations may be beneficial to Data from the CowManager tags indicated that MIN heifers have as additional or alternative means to validate estrus spent more time (P < 0.0001; Table 6) eating compared to alerts generated by the CowManager system. Multiple es- CON with the least amount of min/d eating being observed trus detection technologies [Cowmanager SensOor (Agis by the NRG heifers. Eating behavior can be defined as when Automatisering, Harmelen, the Netherlands), HR Tag (SCR a cow had eating jaw movements and the muzzle was in close Engineers Ltd., Netanya, Israel), Ice-Qube (IceRobotics contact with the ground (Nielsen, 2013; Pereira et al., 2018). Ltd., Edinburgh, UK), DVM bolus (DVM Systems, LLC, Furthermore, NRG heifers spent more time (P < 0.0001) Greeley, CO) and The Track a Cow (Animart Inc., Beaver ruminating compared with CON and MIN heifers. Pereira et Dam, WI)] have been validated on dairy cattle (Dolecheck al. (2018) defined rumination as when a cow was standing, et al., 2015), in which all activity measures increased during walking, or lying and the cow regurgitated a bolus and chewed estrus compared with animals not in estrus. Additionally, the cud while moving her head and jaw in a circular motion these validations have analyzed correlations among dif- and then swallowing the masticate. Heifers consuming NRG ferent technologies on the same animal or comparing human supplement spent more time (P < 0.0001) not being active observations of estrus or activity measures. Nevertheless, compared with MIN (180.8  min/d) being intermediate and the current study did not evaluate additional technologies CON (175.6  min/d) heifers spending the least amount of to compare estrus activity, did not have visual observation, time not active. Conversely, CON heifers were most active and was not evaluated as an indicator of estrus for first- (234.7 min/d; P < 0.0001) compared to MIN being interme- service AI. diate and NRG heifers being the less active compared to other The retrospective evaluation of health alerts generated treatments (200.5 and 187.6  min/d, respectively). Mineral via the CowManager system revealed 34 out of 60 heifers Table 6. Activity of heifers monitored using CowManager ear tags while grazing native range and access to mineral (MIN) or energy with mineral (NRG) supplements Treatment Parameter , min/d CON MIN NRG SEM P-value b c a Eating 535.3 572.6 497.3 5.57 <0.0001 a a b Ruminating 352.2 345.4 393.3 4.13 <0.0001 a b c Not active 175.6 180.8 198.7 1.83 <0.0001 c b a Active 234.7 200.5 187.6 5.04 <0.0001 b a c Highly active 144.4 141.1 165.3 1.17 <0.0001 a,b Means within a row with a different superscript differ (P ≤ 0.05). Treatments include: CON (N= 29), no access to feed supplements; MIN (N = 18), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 13), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. Parameters from the CowManager system (CowManager B.V, the Netherlands) are collected continuously and each minute is classified into behavioral categories (i.e., “eating”, “ruminating”, “not active”, “active”, and “highly active”) using a proprietary model. Precision management of beef heifers 9 generated 146 health alerts, but only 3 heifers of the heifers and Education Graduate Research Assistantship programs initiating an electronic health alert needed clinical treatment for their support for this effort. Appreciation is expressed to (each for symptoms associated with foot rot). Animal care personnel at the Central Grasslands Research and Extension staff identified an additional nine heifers that required treat- Center for assistance with animal handling and forage col- ment for foot rot for which no health alert was generated by lection, and the NDSU Animal Science Nutrition Laboratory. the CowManager system. On a beef operation, to minimize loss of health costs, it is essential to observe behavioral and CONFLICT OF INTEREST STATEMENT physiological changes as early as possible. Therefore, utilizing automatic monitoring of activity and feeding behavior can None declared. provide producers and researchers with an early warning tool (Bikker et al., 2014). However, utilizing sensor monitoring systems requires the producer or researcher to rely on their in- LITERATURE CITED tuition and experience (herdsmanship) when interpreting the Ahola, J. K., D. S. Baker, P. D. Burns, R. G. Mortimer, R. M. Enns, J. C. available information to make intervention decisions (Rutten Whittier, T. W. Geary, and T. E. Engle. 2004. Effect of copper, zinc, et al., 2013). 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Our objectives were to develop a Mobile Cow Command 75:543–550. doi:10.2527/1997.752543x Center (MCCC) for monitoring heifers on native range specif- Cappellozza, B. I., R. F. Cooke, T. A. Guarnieri Filho, and D. W. Bohnert. 2014a. Supplementation based on protein or energy ingredients to ically to 1) examine the relationship between mineral and en- beef cattle consuming low-quality cool-season forages: I. Forage ergy supplementation on intake, liver mineral concentrations, degradability parameters in rumen-fistulated steers and physio- and metabolites and 2) examine activity, reproductive, and logical responses in pregnant heifers. J. Anim. Sci. 92:2716–2724. health behavior. The MCCC units were deployed successfully doi:10.2527/jas.2013-7441 and serve as portable units that use solar power to run indi- Cappellozza, B. I., R. F. Cooke, M. M. Reis, P. Moriel, D. H. Keisler, and vidual components and upload data to cloud-based data acqui- D. W. Bohnert. 2014b. Supplementation based on protein or en- sition platforms. Though not all assigned heifers voluntarily ergy ingredients to beef cattle consuming low-quality cool-season consumed feed from electronic feeders, the SmartFeed units forages: II. Performance, reproductive, and metabolic responses were able to control intake of individual animals assigned to of replacement heifers. J. Anim. Sci. 92:2725–2734. doi:10.2527/ different treatments in a group pasture scenario. Our results jas.2013-7442 clearly show the ability of the electronic feeders to control Ciccioli, N. H., S. L. Charles-Edwards, C. Floyd, R. P. Wettemann, H. T. Purvis, K. S. Lusby, G. W. Horn, and D. L. Lalman. 2005. Inci- intake for precision feeding of individuals in extensive group dence of puberty in beef heifers fed high- or low-starch diets for managed scenarios. The potential exists to develop targeted different periods before breeding1. J. Anim. 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Wilson, K. H. Ominski, and K. M. Wittenberg. 2008. Com- farms. J. Dairy Sci. 96:1928–1952. doi:10.3168/jds.2012-6107 parison of techniques for estimation of forage dry matter intake by Schauer, C. S., K. K. Sedivec, M. L. Bauer, W. D. Slanger, and G. P. Lardy. grazing beef cattle. Can. J. Anim. Sci. 88:693–701. doi:10.4141/ 2004. Self-limiting supplements fed to cattle grazing native mixed- cjas08041 grass prairie in the northern Great Plains. J. Anim. Sci. 82:298–306. Van Soest, P. J., J. B. Robertson, and B. A. Lewis. 1991. Methods for doi:10.2527/2004.821298x dietary fiber, neutral detergent fiber, and nonstarch polysaccharides Schillo, K. K., J. B. Hall, and S. M. Hileman. 1992. Effects of nutrition in relation to animal nutrition. J. Dairy Sci. 74:3583–3597. and season on the onset of puberty in the beef heifer. J. Anim. Sci. doi:10.3168/jds.S0022-0302(91)78551-2 70:3994–4005. doi:10.2527/1992.70123994x Vonnahme, K. A., C. O. Lemley, J. S. Caton, and A. M. Meyer. 2015. Senger, P. L. 1994. The estrus detection problem: New concepts, Impacts of maternal nutrition on vascularity of nutrient transferring technologis, and possibilities. J. Dairy Sci. 77:2745–2753. tissues during gestation and lactation. Nutrients. 7:3497–3523. doi:10.3168/jds.S0022-0302(94)77217-9 doi:10.3390/nu7053497 Smith, S. C., G. A. Highfill, D. E. Cooper, J. A. Smith, and R. P. Wolfger, B., E. Timsit, E. A. Pajor, N. Cook, H. W. Barkema, and K. Wettemann. 2016. Case study: frequency of visits to a mineral Orsel. 2015. Technical note: accuracy of an ear tag-attached accel- feeder by steers grazing wheat pasture. Prof. Anim. Sci. 32:106– erometer to monitor rumination and feeding behavior in feedlot 109. doi:10.15232/pas.2015-01432 cattle. J. Anim. Sci. 93:3164–3168. doi:10.2527/jas.2014-8802 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Translational Animal Science Oxford University Press

Using precision tools to manage and evaluate the effects of mineral and protein/energy supplements fed to grazing beef heifers

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© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.
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Translational Animal Science, 2023, 7, 1–11 https://doi.org/10.1093/tas/txad013 Advance access publication 28 January 2023 Technology in Animal Science Using precision tools to manage and evaluate the effects of mineral and protein/energy supplements fed to grazing beef heifers †,1 † |‡ †,2, Kacie L. McCarthy, Sarah R. Underdahl, Michael Undi, and Carl R. Dahlen Center for Nutrition and Pregnancy and Department of Animal Sciences, North Dakota State University, Fargo, ND, USA |‡ Central Grasslands Research Extension Center, North Dakota State University, Streeter, ND, USA Present address: Department of Animal Science, University of Nebraska, Lincoln, NE 68583, USA Corresponding author: carl.dahlen@ndsu.edu ABSTRACT Our objectives were to develop a Mobile Cow Command Center (MCCC) capable of precision monitoring of grazing heifers to 1) examine the relationship between supplement intake on concentrations of liver mineral and blood metabolites and 2) examine activity, reproductive, and health behavior. Yearling crossbred Angus heifers (N = 60; initial BW = 400.4 ± 6.2 kg) were fitted with radio frequency identification ear tags that allowed access to electronic feeders (SmartFeed system; C-Lock Inc., Rapid City, SD), and with activity monitoring tags (CowManager B.V., the Netherlands) that monitored reproductive, feeding, and health-associated behaviors. Heifers were assigned randomly to one of three treatments for a 57-day monitoring period: 1) no supplement (CON; N = 20), 2) free choice mineral (MIN; Purina Wind and Rain Storm [Land O’Lakes, Inc.], N = 20), or 3) free choice energy and mineral supplement (NRG; Purina Accuration Range Supplement 33 with added MIN [Land O’Lakes, Inc.], N = 20). Consecutive day body weights, blood, and liver biopsies were collected at pasture turnout and final day of monitoring. By design, mineral intake was greatest in MIN heifers (49 ± 37 g/d) and energy supplement intake was greatest in NRG heifers (1,257 ± 37 g/d). Final BW and ADG were similar among treatments (P > 0.42). Concentrations of glucose on day 57 were greater (P = 0.01) in NRG compared with CON and MIN heifers. Liver concentrations of Se and Fe on day 57 were greater (P < 0.05) in NRG heifers than CON, with MIN being intermediate. Activity tags reported NRG heifers spent less time eating (P < 0.0001) and more time (P < 0.0001) being “highly active” than MIN with CON heifers being intermediate. Data retrieved from activity tags identified 16 of 28 pregnant heifers exhibiting some type of estrus-associated behavior even after confirmation of established pregnancy. The activity monitoring system triggered a total of 146 health alerts from 34 of the 60 heifers monitored, but only 3 heifers of the heifers initiating an electronic health alert needed clinical treatment. However, animal care staff identified nine additional heifers that required treatment for which no electronic health alert was generated. The electronic feeders successfully controlled intake of indi- vidual heifers managed in groups pastures; however, the activity monitoring system misrepresented estrus and health events. Key words: activity monitoring, beef cattle, electronic feeder, mineral, supplement, grazing INTRODUCTION and to offset forage nutritive decline throughout the grazing season (Schauer et al., 2004; Cline et al., 2009; McCarthy et Technology continues to improve and some sectors of agri- al., 2021). An issue observed with providing supplements on culture are rapidly implementing new innovations into di- pasture is the large variability in consumption by individuals verse applications. The beef industry, however, is slower than within a group (Tait and Fisher, 1996; Bowman and Sowell, other agricultural industries in rate of adoption (Dahlen et al., 1997; Cockwill et al., 2000; Patterson et al., 2013), which 2014; Lamb et al., 2016). Several reasons likely exist for this is largely unseen and unknown by cattle management per- adoption lag, foremost of which are the lack of comprehen- sonnel. In addition, frequent observation of activity and re- sive technological solutions that can be implemented in ex- productive behavior of grazing cattle is often difficult due to pansive pasture settings, and the lack of solutions from which the expansive nature of pastures and being labor intensive management decisions can be made over the life of an animal. (Elischer et al., 2013). Electronic systems that can monitor Individual animals within a herd of cattle are unique, are in feeding, physical activity, and reproductive-related behavior varying stages of production, have specific nutritional needs, are now available. and present differing health statuses. Within the herd, indi- Activities reported in this study are aimed at developing vidual animal variation exists and changes throughout the a system (the Mobile Cow Command Center) that pairs production year, presenting real and relevant management is- multiple technologies into a single portable unit that would sues for progressive producers. allow for precision management of individuals within a herd Producers often provide mineral and/or protein and energy on expansive pastures to optimize production efficiency, supplements to grazing cattle to maintain targeted produc- improve animal health, and enhance profitability. Our tion goals for growth and reproductive performance (Schillo objectives were to develop a Mobile Cow Command Center et al., 1992; Ciccioli et al., 2005; Cappellozza et al., 2014) (MCCC) for monitoring heifers on native range specifically Received December 13, 2022 Accepted January 25, 2023. © The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. 2 McCarthy et al. to 1) examine the relationship between mineral and energy Training Period supplementation on intake, liver mineral concentrations, Two heifer development pens (N = 63 per pen) were utilized and metabolites and 2) examine activity, reproductive, and at the CGREC for a 2-week training period where one MCCC health behavior. unit was placed in each dry lot pen. A portion of the heifer development ration (corn silage) was placed into the feed bins and heifer intake was monitored. Only heifers with a history MATERIALS AND METHODS of feed consumption from the feeders were selected as exper- All animal procedures were approved by the Institutional imental units for this experiment. Animal Care and Use Committee at North Dakota State University (A18069). Heifer Selection All heifers were estrus synchronized using a controlled in- Study Area ternal drug release (CIDR; Zoetis, Parsippany, NJ) protocol Research was conducted at the Central Grasslands Research (7 d CO-Synch plus CIDR), with heifers receiving 2  mL in- Extension Center (CGREC), located near Streeter, ND from tramuscularly GnRH (Factrel; Zoetis, Parsippany, NJ) and July 25 to September 19. This area is characterized by a con- CIDR insert on day 0. Seven days later, the CIDR insert was tinental climate with warm summers and cold winters with a removed and a single injection of PGF (5  mL intramuscu- 2α majority (72%) of precipitation occurring between May and larly; Lutalyse; Zoetis, Parsippany, NJ) were administered September (Limb et al., 2018). August is the warmest month followed by GnRH and artificial insemination (AI), approxi- with a mean temperature of 18.6°C (NDAWN, 2017). mately 60 h later. All heifers received an estrus detection patch The pasture was 70 ha with a stocking rate of 1.99 Animal (Estrotect; Rockway Inc., Spring Valley, WI) to monitor estrus Unit Months (AUMs)/ha. The vegetation is classified as mixed- (Hill et al., 2014). On the day of AI, final heifer selection for grass prairie dominated by western wheatgrass (Pascopyrum the experiment was made based on 1) history of consuming smithii [Rydb.] À. Löve), green needlegrass (Nassella viridula feed from SmartFeed feeders and 2) activated estrus detection [Trin.] Barkworth) and blue grama (Bouteloua graciles [Willd. patches. A total of 60 of the 126 heifers met the criteria for ex Kunth] Lag. ex Griffiths). Other important species include inclusion in the experiment and were bred using sexed semen sedges (Carex spp.), prairie junegrass (Koeleria macrantha (Tehama Tahoe B767 14AN502) for female offspring. [Ledeb.] Schult.), sages (Artemisia spp.), goldenrods (Solidago spp.), kentucky bluegrass (Poa pratensis L.) a nonnative grass Grazing Period and western snowberry (Symphoricarpos occidentalis Hook.) a native shrub (Limb et al., 2018). Sixty crossbred yearling Angus heifers (initial BW = 400  ±  6  kg) were managed as a single pasture group with Mobile Cow Command Center Units free access to graze native range and were randomly assigned Each of two Mobile Cow Command Center (MCCC) units to 1 of 3 dietary treatments 1) no access to feed supplements were developed by pairing two commercially available (CON; N = 20), 2) free choice access to mineral supplement technologies into single trailer units that can be transported (MIN; Purina Wind & Rain Storm All-Season 7.5 Complete, and function anywhere cattle are managed. The first tech- Land O’Lakes, Inc., Arden Hills, MN, N = 20), or 3) free nology is the SmartFeed device (C-lock Inc., Rapid City, SD), choice access to energy supplement (NRG; Purina Accuration which is a self-contained system designed to measure supple- Range Supplement 33, Land O’Lakes, Inc., Arden Hills, MN, ment intake and feeding behavior from individual cattle in N = 20). The manufacturer recommendation for daily intake group settings. The system is solar powered and includes a of the mineral supplement was 113 g. The NRG supplement radio-frequency identification (RFID) reader, weigh scales, was formulated by adding 68.1 kg MIN to a 907.4 kg mix- access control gate, a feed bin, and a cloud-based interface ture of 60% ground corn and 40% Accuration (25.5 % CP; which continuously logs feed intake and feeding behavior Table 1) with an anticipated daily intake of 1.63  kg. Thus, data. The programming of the SmartFeed units is flexible, if heifers in the NRG treatment consumed 1.63  kg of sup- with the ability to assign specific animals to specific feeders plement, and heifers in the MIN treatment consumed 113 g, and to prohibit entry of individual animals once a daily target then both the MIN and NRG heifers would be consuming intake is achieved. The second technology included in the the same amount of the mineral product used. The MIN MCCC was the CowManager system (CowManager B.V., the and NRG supplements were delivered via the MCCC units Netherlands), which fits over an RFID ear tag and uses ad- which were located within 50 m of the waterer in the pasture. ditional sensors to monitor cow reproductive (estrus alerts), Feeders were set to restrict access of CON heifers from either feeding-related (eating, rumination, and activity level), and trailer unit, with MIN and NRG heifers having ad libitum ac- health-associated data. The CowManager ear tag continu- cess to the trailer containing their respective feed assignment. ously registers movements from the cow’s ear and classifies Because few heifers consumed either supplement early in the the data through proprietary algorithms (Pereira et al., 2018). grazing season (Figure 1), feed intake data were summarized Data are sent through a wireless connection, via a router over a 57-d period; from the time of pregnancy diagnosis placed on the top of the MCCC unit. Data are then received (July 25) until removal from pasture (September 19). through a coordinator unit that is attached to a computer in a The CowManager system reported the minutes spent lab (approximately 200 m line of site from the MCCC units) during each hour of every day in activity categories in- that automatically uploaded the data for viewing on any de- cluding “eating”, “ruminating”, “not active”, “active”, vice with an internet connection. Each MCCC contained 2 and “highly active”, with a proprietary model and avail- SmartFeed units, controlling hardware and the CowManager able through the web-based application. Estrus-related router in an enclosed trailer with open feed access areas and alerts were continuously generated via the CowManager retractable wheels for transport. system, including classifications of “in heat”, “potential”, or Precision management of beef heifers 3 Table 1. Dietary ingredient and nutrient composition of mineral (MIN) and were dried in a forced-air oven at 60°C for at least 48 h and energy with mineral (NRG) supplement fed to grazing beef heifers then ground to pass through a 2-mm screen using a Wiley mill (Arthur H. Thomas, Philadelphia, PA). Clipped forage % DM basis samples for each location reported herein were composite 1 2 Nutrient analysis NRG MIN over all locations within the representative sampling date and reported as averages within month. Forage samples were DM 94.95 — analyzed at the North Dakota State University Nutrition Ash 12.69 — Laboratory for dry matter (DM), ash, N (Kjehldahl method), CP 25.49 — Ca, P, and ether extract (EE) by standard procedures (AOAC, N 4.08 — 1990). Crude protein (CP) was calculated by multiplying N NDF 15.77 — by 6.25. Neutral detergent fiber (NDF) and acid detergent ADF 5.78 — fiber (ADF) concentrations were determined by the modi- Ether extract 6.17 — fied method of Van Soest et al. (1991) using a fiber analyzer Mineral analysis, mg/kg (Ankom Technology Corp., Fairport, NY). Samples were also analyzed for Cu, Zn, Co, Mo, Fe, S, and Se using inductively Ca 18,499 176,939 coupled plasma optical emission spectroscopy (ICP-OES) P 10,047 76,274 by the Veterinary Diagnostic Laboratory at Michigan State S 7,150 8,165 University. Se <100.0 <100.0 Fe 462 6,628 Liver Sample Collection and Analysis Cu 1,079 796.3 Because the liver is a major organ of mineral storage and Zn 429.9 2,590.5 concentrations of minerals in the liver are indicative of min- Mo 8.6 15.7 eral status in ruminants (Spears et al., 2022), liver samples were collected at pasture turnout and at the final day of Mn 202.6 2,860.4 monitoring via biopsy from a subset of heifers from each re- Co 67.14 10.35 spective treatment (N = 24, 8 per treatment). Liver biopsy samples (approximately 20 mg) were collected as previously NRG = Purina Accuration Range Supplement 33 with added MIN (Purina Wind & Rain Storm All-Season 7.5 Complete; Land O’Lakes, Inc., Arden described by McCarthy et al. (2020). Liver samples frozen Hills, MN). Formulated by adding 68.1 kg MIN to a 907.4 kg mixture of at −20°C, then sent on ice to the Veterinary Diagnostic 60% ground corn and 40% Accuration. MIN = Purina Wind & Rain Storm All-Season 7.5 Complete (Land Laboratory at Michigan State University and were evaluated O’Lakes, Inc., Arden Hills, MN). Ingredients: Dicalcium Phosphate, for concentrations of minerals using inductively coupled Monocalcium Phosphate, Calcium Carbonate, Salt, Processed Grain plasma mass spectrometry (ICP-MS). ByProducts, Vegetable Fat, Plant Protein Products, Potassium Chloride, Magnesium Oxide, Vitamin E Supplement, Vitamin A Supplement, Natural and Artificial Flavors, Calcium Lignin Sulfonate, Ethoxyquin Blood Collection and Serum Analysis (a Preservative), Manganese Sulfate, Vitamin D3 Supplement, Zinc Blood metabolites were analyzed from a subset of heifers Sulfate, Basic Copper Chloride, Ethylenediamine Dihydroiodide, Cobalt Carbonate. The vitamin was labeled to contain 136,054, 13,605, and 136 from each respective treatment (N = 30). Blood samples were IU/kg of Vitamins A, D, and E, respectively. 3 collected at pasture turnout and at the final day of monitoring Analysis for concentrations of trace minerals was done using an ICP-OES panel for premix evaluation with the lowest detection limit for Se of via jugular venipuncture into serum tubes (10  mL; Becton 100 mg/kg. Company guaranteed analysis for concentrations of Se in MIN Dickinson Co., Franklin Lakes, NJ), allowed to clot for supplement was 27 mg/kg. 30  min and centrifuged at 1,500 × g at 4°C for 20  min. Serum was separated and stored in plastic vials at −20°C “suspicious”. Pregnancy detection was performed 34 d after until further analysis. Serum samples were analyzed for glu- AI via transrectal ultrasonography (7.0-MHz transducer, 500 cose and NEFA. Samples were analyzed using the Synergy H1 V Aloka, Wallingford, CT). Continuous monitoring with Microplate Reader (Biotek, Winooski, VT) with the Infinity the CowManager tag provided data related to heifer estrus Glucose Hexokinase Kit (Thermo Scientific, Waltham, MA) activity. A retrospective analysis was conducted to deter- and NEFA-C Kit (WAKO Chemicals, Inc., Richmond, VA). mine the accuracy of estrus-related alerts generated via the The intra- and interassay CV was 2.62% and 3.41%, for CowManager system versus a known pregnancy status de- serum glucose, respectively and 7.75% and 8.29%, for serum termined via ultrasound. Similarly, a retrospective analysis NEFA, respectively. was conducted to evaluate the accuracy of health events that Statistical Analysis were flagged via the CowManager system (reported as “sick”, “very sick”, or “no movement”) by comparing electronic Heifers assigned to MIN and NRG treatments that did not alerts with treatment logs generated by the animal care staff. voluntarily consume their assigned supplements from the It is important to note that the CowManager system has been electronic feeders were retrospectively added to CON treat- validated using the proprietary algorithm in populations of ment for analysis, resulting in a final N of 29 CON, 18 MIN dairy cows housed indoors (Bikker et al., 2014) and grazing ,and 13 NRG heifers, respectively. Data were analyzed as a (Pereira et al., 2018). completely randomized design with heifer used as the ex- perimental unit for all analysis. Performance and intake Forage Collection and Analysis data were analyzed using the GLM procedure of SAS (9.4, Forage samples were obtained every 2 weeks from 20 dif- SAS Inst. Inc., Cary, NC) with treatment as the fixed effect. ferent locations in the pasture in a diagonal line across the Blood metabolites were also analyzed using the GLM pro- pasture. The forage samples were hand clipped to a height cedure and the model statement used contained the effects of 3.75 cm above ground (Undi et al., 2008). Forage samples of treatment and baseline serum metabolite concentrations 4 McCarthy et al. Figure 1. Daily intake of mineral (MIN) or energy with mineral (NRG) supplements of heifers grazing native range over the duration of the grazing season. The 57-d monitoring period was initiated from the time of pregnancy diagnosis (July 25th) until removal from pasture (September 19th). Treatments include: MIN (N = 18), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 13), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. at pasture turnout. Concentrations of mineral in liver attended feeders compared with MIN (2.1 ± 0.6 min/d) and samples were analyzed using the GLM procedure and the CON heifers (1.3  ±  0.6  min/d). Additionally, NRG heifers model statement used contained the effect of treatment, with visited the feeders more (P < 0.001) times (9.20  ±  0.34 values from baseline pasture turnout liver samples used as times/d) on days they attended feeders compared with MIN a covariate. Total mineral intake from supplemental sourced (2.71 ± 0.34 times/d) and CON heifers (1.94 ± 0.34 times/d). was calculated by multiplying total supplement intake over Over the 57-day monitoring period, heifers in the MIN the 57-day monitoring period by the analyzed concentration treatment consumed 49.3  ±  37  g/d of mineral supplement. of the respective supplement (MIN or NRG) consumed by Heifers in the NRG treatment consumed 1,257.1 ± 37 g/d of individual heifers. Total mineral intake data were analyzed energy supplement. Mean values for NRG supplement intake using the GLM procedure of SAS with a model including by heifers in the CON treatment were driven by 3 heifers that treatment. Data for activities including daily time spent consumed a total of 63.3 g/d over the monitoring period at eating, ruminating, not active, active, and highly active were the NRG supplement feeder. Mean values for MIN supple- analyzed using the MIXED procedure of SAS for repeated ment intake by heifers in the CON treatment were driven by measures in time with treatment, day, and their interaction in 26 feeding attempts where 2.8  g/d of MIN supplement was the model. Results are reported as least square means using consumed during 7.7 of the 57 d (13% attendance) during the the LSMEANS statement for liver and plasma. For all anal- monitoring period. Over the monitoring period, NRG heifers ysis, significance was set at P ≤ 0.05. spent more (P < 0.001) time (2.9 ± 0.34 min/d) at the feeder compared with MIN (0.72  ±  0.34  min/d) and CON heifers (0.18  ±  0.34  min/d). Additionally, during the monitoring period, NRG heifers visited the feeders more (P < 0.001) times RESULTS AND DISCUSSION daily (6.18 ± 0.15 times/d) than MIN (2.71 ± 0.15 times/d) Heifer Intake, Feeding Behavior, and Performance and CON heifers (0.25 ± 0.15 times/d). Intake of energy and mineral supplements were minimal Certainly, heifers not assigned to the respective treatments during the early portion of the grazing season but began to did attempt to consume supplement. However, the SmartFeed increase in midAugust as the quality of native range declined system was able to limit the frequency of feeder attendance (Figure 1). Proportion of days attending feeders was greater and supplement consumption by heifers that were not desig- (P < 0.001) for NRG heifers (68  ±  2.04%) compared with nated to consume the respective supplements via that online MIN heifers (41  ±  2.04%). Overall number of days heifers control system. Cows that were being fed in SmartFeed units were present at the NRG and MIN feeders was 38.7 and (McCarthy et al., 2021) consumed more mineral supplement 23.1  ±  1.2 d of the 57 d, respectively. More supplement (P on average (125.4 g/d) than heifers reported herein. In com- < 0.001) was consumed on days that NRG heifers attended parison, Smith et al. (2016) built a custom mineral feeder with feeders (1,877 ± 76 g/d of energy supplement) compared with an RFID reader and reported that steers that had access to a days when MIN heifers attended feeders (122  ±  76  g/d of commercially available free-choice mineral consumed 72 g/d mineral supplement). Energy supplement heifers spent more per head over a 90-d grazing period. The mineral disappear- (P = 0.01) time at the feeders (4.1 ± 0.6 min/d) on days they ance in Smith et al. (2016) was within a range of manufacturer Precision management of beef heifers 5 recommended intakes of 40 to 125 g/head per day. Moreover, ADG (0.75 kg/d) over a 19-day feeding period (Cappellozza researchers in Oklahoma (Reuter et al., 2017) conducted a et al., 2014a). Heifers on the NRG treatment in the current pilot study using the SmartFeed system to characterize the experiment were likely substituting a portion of forage in- daily variation in soybean meal supplement with the inclu- take with the supplement consumed (Summers et al., 2015). sion of salt on intake by group-housed, self-fed grazing steers. Collectively, heifers assigned to the NRG treatment may have Fifteen steers from Reuter et al. (2017) consumed 1,210 g/d simply not consumed enough supplement over the course of of supplement with a 45% salt inclusion for a 14-d period. the experiment to compensate for reduced forage intake and Although steers consumed a similar amount of supplement elicit a subsequent gain response. compared to heifers reported herein, variation among ani- Blood Metabolites mals was also reported with animals visiting 5.1 ± 1.3 times/d over the 14-d period (Reuter et al., 2017). Over the duration Though no gain response was observed, concentrations of this study, heifers visited the feeders a similar number of of glucose in serum were 14% greater (P = 0.01) in NRG times compared with those reported by Reuter et al. (2017) heifers compared with CON and MIN heifers at the end utilizing the same feeder technologies. The variation among of the monitoring period (Table 2). Similar concentrations animals from Reuter et al. (2017) suggests that competition of glucose have been reported in beef heifers offered low- for use of one SmartFeed unit may have been a challenge starch energy supplements daily or three times weekly (76.3 because intervals between different RFID readings (animals and 70.5 mg/dL, respectively; Moriel et al., 2012) or where exchanging places at the feeder) was less than 1  s per an- heifers received either energy (provided as cracked corn, soy- imal. Heifers in the current study may have been experiencing bean meal, and urea) or protein (provided as soybean meal) similar challenges with competition at the feeder even though supplements while consuming cool-season forages (65.0 they had an additional SmartFeed unit to visit. This postulate and 65.1  mg/dL, respectively; Cappellozza et al., 2014b). was corroborated with visual observations of heifers vigor- Since starch is a major dietary precursor for glucose in ously exchanging places at the feeder when the herd did visit ruminants (Huntington, 1997), the observation of elevated the proximity of the feeders. concentrations of glucose in heifers receiving the NRG (i.e. The manufacturer label for the mineral supplement pro- starch-based) supplement was expected. Starch fermenta- vided recommended optimum intakes of 113  g/head daily. tion in the rumen results in greater propionate and less ac- Over the 57-day monitoring period, 1 in 18 (0.06%) MIN etate production, and therefore a greater supply of glucose heifers consumed recommended MIN intake, but heifers did to the animal (Huntington, 1997). Furthermore, other studies not attend feeders daily. On days they did attend the feeder 10 (Cooke et al., 2008) have reported increases in plasma glu- of the 18 (56%) heifers that attended the feeders consumed cose concentration in heifers supplemented infrequently and recommended feeding rates of MIN supplement. Variation attributed those increases to the time required for synthesis in individual consumption has been related to number and and activation of gluconeogentic enzymes to change glucose placement of feeders, individual animal preference, weather, synthesis and released by the liver. individual and herd behavior, characteristics of the feedstuff, There were no differences among treatments in and feed additives that may be included (Tait and Fisher, concentrations of NEFA in serum at the conclusion of 1996; Bowman and Sowell, 1997; Smith et al., 2016). the experiment (P = 0.85; Table 2). Circulating NEFA Overall, heifer final BW was similar among treatments concentrations reflect fat mobilized from body reserves, (433  ±  6  kg; P = 0.42). Interestingly, treatment did not in- with elevated concentrations often associated with negative fluence body weight gain (P = 0.76) during the monitoring energy balance. Nevertheless, it is important to note that period, with heifer ADG equal to 0.46  kg/d. Many studies heifers from all treatments were in a positive nutritional highlight enhanced gain in heifers consuming supplemental status based on similar ADG and, therefore, no mobilization feeds (Delcurto et al., 2000; Engel et al., 2008; Summers of body reserves was likely necessary in any treatments. As et al., 2015). However, previous studies have reported that animals experience compensatory gain, concentrations of neither trace mineral supplementation nor source (organic NEFA have been reported to rapidly decline (Ellenberger et and inorganic) affected cow BW or BCS (Olson et al., 1999; al., 1989). McFarlane et al. (2017) provided protein supple- Muehlenbein et al., 2001; Ahola et al., 2004). Similarly, preg- ment to growing heifers grazing winter forage and reported nant heifers provided an energy supplement as a mixture of no differences in concentrations of NEFA in serum, which cracked corn, soybean meal, and urea while consuming low- was not expected due to the fact that the authors observed quality cool-season forages in feedlot pens reported similar BW changes in heifers. In contrast, Cappellozza et al. (2014b) Table 2. Effects of mineral (MIN) or energy with mineral (NRG) supplements on concentrations of serum metabolites in heifers grazing native range Treatment P-value Item CON MIN NRG SEM TRT NEFA, µmol/L 327.1 326.2 291.7 47.04 0.85 b b a Glucose, mg/dL 66.7 66.5 75.9 2.12 0.01 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 10), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 8), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. Results covariately adjusted to baseline serum sample taken at pasture turnout. 6 McCarthy et al. reported that control heifers had greater concentrations of programming effects on offspring conceived and gestated in NEFA compared with heifers receiving either energy (pro- extensive pasture conditions. vided as cracked corn, soybean meal, and urea) or protein (provided as soybean meal) supplements while consuming Forage Analysis cool-season forages. Although it is important to note that Forage nutrient content appeared to decrease over the course Cappellozza et al. (2014b) reported unexpected differences of the grazing period (Table 3) observed by percentage of with control heifers, all heifers were in a positive nutritional CP decreasing and greater NDF values over the season. As status. Therefore, lack of differences among treatments re- forage nutritive value decreased, we observed increases in ported herein was likely due to heifers not being in negative supplement intakes (Figure 1). A decrease in the forage nu- energy balance through the grazing period. tritive value is typical in diets of grazing cattle during the It is important to note that during the time of supple- advancing season (Bedell, 1971; Johnson et al., 1998; Cline mentation in the current study, heifers were in early stages et al., 2009; McCarthy et al., 2021). Typically, the nutrient of gestation. The maternal gastrointestinal tract is critical availability of grazed forages fluctuates by environmental for nutrient acquisition and is a major nutrient sink during conditions, forage species, soil type and stage of maturity pregnancy (Vonnahme et al., 2015) and the relationship be- (NASEM, 2016). tween maternal nutrient intake during pregnancy and fetal For beef breeding cattle, recommended allowances for growth are extremely important (Redmer et al., 2004; Dahlen Se, Fe, Cu, Zn and Mn are 0.10, 50, 10, 30 and 40 mg/kg et al., 2021; Reynolds et al., 2022). Research from Perry et al. of diet, respectively (NASEM, 2016). Iron in pastures has (1999) determined that low dietary protein (provided as cot- been shown to have seasonal fluctuations with peaks in tonseed meal) in the first trimester of pregnancy followed by spring and autumn (Suttle, 2010), where our current forage increased protein in the second trimester may have an effect Fe concentrations are greater over the course of the grazing on placental development and thus subsequent impacts on season. According to Corah and Dargatz (1996), forage Fe calf body weight in primiparous heifers. In addition, a similar is within adequate levels at 50 to 200 mg/kg. Most forage mineral and protein/energy supplements fed to beef heifers contains 70 to 500  mg Fe/kg (NASEM, 2016), which the during early gestation resulted in altered fetal liver and femur current pasture falls within the range. Concentrations of weights, concentrations of mineral in fetal liver and muscle, Cu in forage were marginal to deficient (4 to 7 vs. < 4 mg/ concentrations of amino acids in the amniotic fluid, and al- kg, respectively; Corah and Dargatz, 1996). Forages vary tered placental gene expression by day 83 of gestation (Diniz in Cu content, with legumes usually having higher content et al., 2021; Menezes et al., 2021; McCarthy et al., 2022; than grasses (NASEM, 2016). Moreover, concentrations of Menezes et al., 2022). Therefore, observations of altered Zn were deficient (<20  mg/kg) until midAugust to early metabolite and mineral profiles as observed in the current September. According to Corah and Dargatz (1996), Mo, experiment may be impacting the developing fetus, and fur- Co, and Mn were adequate (<1, 0.1 to 0.25, and >40 mg/ ther investigation is warranted to determine the potential of kg, respectively). As stated by Suttle (2010), Mn values for using electronic feeding equipment to impose developmental pastures vary, with a mean value of 86 mg/kg. In addition, Table 3. Forage analysis of representative sample composites of pasture grazed by beef heifers provided either mineral (MIN) or energy with mineral (NRG) supplement from June to September Grazing period Item June July August September TDN 60.5 62.0 60.6 58.6 CP, % 9.02 7.1 6.8 5.9 Ash 10.04 9.4 10.3 10.5 NDF, % 62.87 59.1 61.1 64.5 ADF, % 35.9 34.1 35.9 38.4 Ca, % 0.21 0.33 0.41 0.42 P, % 0.40 0.14 0.12 0.10 S, % 0.1416 0.1498 0.1616 0.1503 Se, mg/kg <10.0 <10.0 <10.0 <10.0 Fe, mg/kg <50 101 130 166 Cu, mg/kg 4.6 4.1 4.5 3.8 Zn, mg/kg 14.8 17.7 20.0 23.7 Mo, mg/kg 1.4 1.4 1.7 1.3 Mn, mg/kg 59 60.7 84.0 100.4 Co, mg/kg <1.00 <1.00 <1.00 <1.00 Clipped forage samples from 20 different locations reported herein are composite over all locations within the representative sampling dates. Values presented are mean values of the representative sampling dates within the given month: June (N= 1), July (N = 3), August (N = 2), and September (N = 3). TDN = 88.9 – (0.79 × ADF%); Holland and Kezar, 1995 Precision management of beef heifers 7 Mn requirements for breeding cattle are higher than Liver Mineral Concentrations and Supplemental growing and finishing cattle due to reproduction demands Mineral Intake (NASEM, 2016). At the end of the monitoring period, concentrations of Se and Similar forage responses in the Northern Great Plains Fe in liver of NRG heifers were greater (P = 0.01; Table 4) have been reported by investigators (Johnson et al., 1998; than CON, whereas MIN were intermediate. Concentrations Cline et al., 2009) who have observed increases in forage of liver Co at the end of the monitoring period were greater fiber content with the advancing season. In addition, avail- in NRG heifers (P < 0.001) compared with MIN, which were able forage protein may decrease enough over the grazing greater (P < 0.001) than CON. Furthermore, no differences (P season that optimal livestock performance may require ≥ 0.12) were observed in concentrations of liver Cu, Zn, Mo, supplementation (Bodine et al., 2001). As noted, intakes and Mn among treatments. According to guidelines published of NRG supplement by heifers increased with advancing by Kincaid (2000), liver concentrations of Fe, Zn, Se, Mo, season. Furthermore, mineral intake is often affected by and Mn in all treatment groups were considered adequate at season of the year, with the greatest intakes often during the the end of the grazing period. Additionally, concentrations of winter or dry season when forages stop growing, become liver Co in all treatment groups were above levels considered high in fiber and lignin and low in digestibility (McDowell, to be satisfactory (0.08 to 0.12 μg/g DM; McNaught, 1948). 1996). This was also corroborated with MIN supplemented In contrast, Cu values would be considered marginal (33 heifers that started consuming more supplement later in the to 125 μg/g DM; Kincaid, 2000). The lower concentrations season. Moreover, native forages typically grazed by beef of Cu noted in CON heifers can be supported by the low cattle are generally deficient to marginal in Cu, Mn, Se, and forage value for Cu concentrations reported herein and Zn concentrations (Umoh et al., 1982); therefore, supplying therefore mineral supplementation may result in increased supplemental minerals under these grazing conditions are concentrations of Cu in heifers grazing native range. typically performed. Over the course of the grazing season, Data in the current report align with McDowell (1996) the most notable change in forage mineral concentra- who suggested that the most efficient method for providing tion were noted in decreasing concentrations of Cu, and supplemental minerals may be through a combination with increasing concentrations of Fe, Zn, and Mn. concentrates to ensure that adequate intake of minerals Table 4. Effects of mineral (MIN) or energy with mineral (NRG) supplements on liver mineral concentrations at pasture removal in heifers grazing native range Treatment P-value Item , µg/g CON MIN NRG SEM TRT b a,b a Se 1.40 1.61 1.85 0.118 0.01 b a,b a Fe 197.7 213.0 286.0 28.57 0.05 Cu 75.3 106.0 110.2 16.39 0.12 Zn 99.8 103.3 112.6 8.60 0.47 Mo 3.65 3.93 3.70 0.269 0.58 Mn 9.25 8.99 10.66 0.810 0.27 c b a Co 0.13 0.32 0.41 0.02 <0.001 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 7), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 5), free choice access to energy and mineral supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)] Results covariately adjusted to baseline liver biopsy taken at pasture turnout. Table 5. Total supplemental mineral intake in heifers consuming mineral (MIN) or energy with mineral (NRG) supplements over a 57-d period Treatment P-value Item, g CON MIN NRG SEM TRT c b a Fe 1.1 18.6 33.1 1.96 <0.0001 b b a Cu 0.5 2.2 77.3 2.69 <0.0001 c b a Zn 0.5 7.3 30.8 1.23 <0.0001 b b a Mo 0.005 0.044 0.616 0.022 <0.0001 c b a Mn 0.48 8.04 14.52 0.852 <0.0001 b b a Co 0.026 0.029 4.81 0.167 <0.0001 a,b Means within a row with a different superscript differ (P < 0.05). Treatments include: CON (N = 12), no access to feed supplements; MIN (N = 7), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 5), free choice access to energy and mineral supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. 8 McCarthy et al. along with other nutrients are consumed. This strategy can and CON heifers spent a similar amount of time being be effective in decreasing the variability in free-choice trace highly active (141.1 and 141.4  min/d, respectively), with mineral intake and bolstering tissue stores during winter NRG heifers spending 20 more minutes being highly active or when energy/protein supplements are provided. The (165.3  min/d; P < 0.0001) compared with other treatments. NRG treatment in the current experiment was formulated Heifers reported herein were moving throughout the pasture so that at a projected intake level, heifers would consume as a herd of 60 cattle, which may explain the high level of the same 113  g/head daily of the same mineral source the activity reported from the 13 NRG heifers as they competed MIN heifers were receiving. Though NRG heifers did not for supplement from the 2 feeder spaces in the MCCC units. achieve the anticipated intake, they ultimately consumed The CowManager system has been validated for rumination greater (P < 0.0001; Table 5) amounts of supplemental and activity measures in dairy cattle kept in freestalls (Bikker Fe, Cu, Zn, Mo, MN, and Co compared with MIN heifers et al., 2014), or grazing (Pereira et al., 2018), and with feedlot that just had free choice access to the mineral supplement. cattle in confinement (Wolfger et al., 2015). However, there Therefore, increased liver concentrations of Co for NRG is paucity of data related to beef cattle managed in extensive heifers compared with MIN heifers were not unexpected. grazing scenarios. Also, NRG heifers consumed 77.96% more Fe compared to The retrospective evaluation of estrus alerts generated total supplemental mineral intake in MIN heifers, therefore via the CowManager system revealed that 16 of 28 heifers corroborating the increased concentrations of Fe in the liver (57%) confirmed pregnant via ultrasound were incorrectly of NRG heifers. In addition, because a majority of NRG identified as displaying some type of estrus behavior (two consumption was late in the monitoring period, we antici- reported as in heat, 11 reported as potential, and three re- pate that if heifers were allowed to continue their respective ported as suspicious). If producers were using this tech- treatments for additional time that concentrations of other nology for estrus detection in a pasture setting, additional liver minerals would subsequently diverge between the MIN confirmation of estrus behavior would be important to and NRG heifers. consider for use in AI breeding. Additional resources such as estrus detection patches to determine heat state (Hill Activity Monitoring T ags et al., 2014) or visual observations may be beneficial to Data from the CowManager tags indicated that MIN heifers have as additional or alternative means to validate estrus spent more time (P < 0.0001; Table 6) eating compared to alerts generated by the CowManager system. Multiple es- CON with the least amount of min/d eating being observed trus detection technologies [Cowmanager SensOor (Agis by the NRG heifers. Eating behavior can be defined as when Automatisering, Harmelen, the Netherlands), HR Tag (SCR a cow had eating jaw movements and the muzzle was in close Engineers Ltd., Netanya, Israel), Ice-Qube (IceRobotics contact with the ground (Nielsen, 2013; Pereira et al., 2018). Ltd., Edinburgh, UK), DVM bolus (DVM Systems, LLC, Furthermore, NRG heifers spent more time (P < 0.0001) Greeley, CO) and The Track a Cow (Animart Inc., Beaver ruminating compared with CON and MIN heifers. Pereira et Dam, WI)] have been validated on dairy cattle (Dolecheck al. (2018) defined rumination as when a cow was standing, et al., 2015), in which all activity measures increased during walking, or lying and the cow regurgitated a bolus and chewed estrus compared with animals not in estrus. Additionally, the cud while moving her head and jaw in a circular motion these validations have analyzed correlations among dif- and then swallowing the masticate. Heifers consuming NRG ferent technologies on the same animal or comparing human supplement spent more time (P < 0.0001) not being active observations of estrus or activity measures. Nevertheless, compared with MIN (180.8  min/d) being intermediate and the current study did not evaluate additional technologies CON (175.6  min/d) heifers spending the least amount of to compare estrus activity, did not have visual observation, time not active. Conversely, CON heifers were most active and was not evaluated as an indicator of estrus for first- (234.7 min/d; P < 0.0001) compared to MIN being interme- service AI. diate and NRG heifers being the less active compared to other The retrospective evaluation of health alerts generated treatments (200.5 and 187.6  min/d, respectively). Mineral via the CowManager system revealed 34 out of 60 heifers Table 6. Activity of heifers monitored using CowManager ear tags while grazing native range and access to mineral (MIN) or energy with mineral (NRG) supplements Treatment Parameter , min/d CON MIN NRG SEM P-value b c a Eating 535.3 572.6 497.3 5.57 <0.0001 a a b Ruminating 352.2 345.4 393.3 4.13 <0.0001 a b c Not active 175.6 180.8 198.7 1.83 <0.0001 c b a Active 234.7 200.5 187.6 5.04 <0.0001 b a c Highly active 144.4 141.1 165.3 1.17 <0.0001 a,b Means within a row with a different superscript differ (P ≤ 0.05). Treatments include: CON (N= 29), no access to feed supplements; MIN (N = 18), free choice access to mineral supplement [Purina Wind & Rain Storm All-Season 7.5 Complete (Land O’Lakes, Inc., Arden Hills, MN)]; NRG (N = 13), free choice access to energy supplement [Purina Accuration Range Supplement 33 with added MIN (Land O’Lakes, Inc., Arden Hills, MN)]. Parameters from the CowManager system (CowManager B.V, the Netherlands) are collected continuously and each minute is classified into behavioral categories (i.e., “eating”, “ruminating”, “not active”, “active”, and “highly active”) using a proprietary model. Precision management of beef heifers 9 generated 146 health alerts, but only 3 heifers of the heifers and Education Graduate Research Assistantship programs initiating an electronic health alert needed clinical treatment for their support for this effort. Appreciation is expressed to (each for symptoms associated with foot rot). Animal care personnel at the Central Grasslands Research and Extension staff identified an additional nine heifers that required treat- Center for assistance with animal handling and forage col- ment for foot rot for which no health alert was generated by lection, and the NDSU Animal Science Nutrition Laboratory. the CowManager system. On a beef operation, to minimize loss of health costs, it is essential to observe behavioral and CONFLICT OF INTEREST STATEMENT physiological changes as early as possible. Therefore, utilizing automatic monitoring of activity and feeding behavior can None declared. provide producers and researchers with an early warning tool (Bikker et al., 2014). However, utilizing sensor monitoring systems requires the producer or researcher to rely on their in- LITERATURE CITED tuition and experience (herdsmanship) when interpreting the Ahola, J. K., D. S. Baker, P. D. Burns, R. G. Mortimer, R. M. Enns, J. C. available information to make intervention decisions (Rutten Whittier, T. W. Geary, and T. E. Engle. 2004. Effect of copper, zinc, et al., 2013). These technologies provide benefits to producers and manganese supplementation and source on reproduction, min- and researchers when they can easily monitor cattle without eral status, and performance in grazing beef cattle over a two-year disturbing natural behavior; however, technologies must ac- period. J. Anim. Sci. 82:2375–2383. doi:10.2527/2004.8282375x curately and easily quantify behavioral and physiological AOAC. 1990. Official methods of analysis. 15th ed. Arlington, VA: As- sociation of Official Analytical Chemists. parameters (Senger, 1994). Some monitoring systems for ru- Bedell, T. E. 1971. Nutritive value of forage and diets of sheep and mination and estrus have been validated with high accuracy in cattle from oregon subclover-grass mixtures. J. Range Manage. dairy cattle (Bikker et al., 2014; Dolecheck et al., 2015); how- 24:125–133. doi:10.2307/3896521 ever, validation of rumination collars in beef cattle resulted Bikker, J. P., H. van Laar, P. Rump, J. Doorenbos, K. van Meurs, G. in underestimated rumination times (Goldhawk et al., 2013). M. Griffioen, and J. Dijkstra. 2014. Technical note: evaluation of More research is required to refine the algorithms for esti- an ear-attached movement sensor to record cow feeding behavior mation of activity and behavioral parameters when used in and activity. J. Dairy Sci. 97:2974–2979. doi:10.3168/jds.2013- beef cattle grazing extensive pastures. Having a more refined algorithm for grazing beef cattle may enhance monitoring of Bodine, T. N., H. T. Purvis, and D. L. Lalman. 2001. Effects of sup- estrus and health events in beef cattle production systems. plement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle. J. Anim. Sci. 79:1041–1051. doi:10.2527/2001.7941041x Bowman, J. G. P., and B. F. Sowell. 1997. Delivery method and supple- CONCLUSIONS ment consumption by grazing ruminants: a review. J. Anim. Sci. Our objectives were to develop a Mobile Cow Command 75:543–550. doi:10.2527/1997.752543x Center (MCCC) for monitoring heifers on native range specif- Cappellozza, B. I., R. F. Cooke, T. A. Guarnieri Filho, and D. W. Bohnert. 2014a. Supplementation based on protein or energy ingredients to ically to 1) examine the relationship between mineral and en- beef cattle consuming low-quality cool-season forages: I. Forage ergy supplementation on intake, liver mineral concentrations, degradability parameters in rumen-fistulated steers and physio- and metabolites and 2) examine activity, reproductive, and logical responses in pregnant heifers. J. Anim. Sci. 92:2716–2724. health behavior. The MCCC units were deployed successfully doi:10.2527/jas.2013-7441 and serve as portable units that use solar power to run indi- Cappellozza, B. I., R. F. Cooke, M. M. Reis, P. Moriel, D. H. Keisler, and vidual components and upload data to cloud-based data acqui- D. W. Bohnert. 2014b. Supplementation based on protein or en- sition platforms. Though not all assigned heifers voluntarily ergy ingredients to beef cattle consuming low-quality cool-season consumed feed from electronic feeders, the SmartFeed units forages: II. Performance, reproductive, and metabolic responses were able to control intake of individual animals assigned to of replacement heifers. J. Anim. Sci. 92:2725–2734. doi:10.2527/ different treatments in a group pasture scenario. Our results jas.2013-7442 clearly show the ability of the electronic feeders to control Ciccioli, N. H., S. L. Charles-Edwards, C. Floyd, R. P. Wettemann, H. T. Purvis, K. S. Lusby, G. W. Horn, and D. L. Lalman. 2005. Inci- intake for precision feeding of individuals in extensive group dence of puberty in beef heifers fed high- or low-starch diets for managed scenarios. The potential exists to develop targeted different periods before breeding1. J. Anim. Sci. 83:2653–2662. management strategies for cattle with distinct nutrient needs doi:10.2527/2005.83112653x (i.e., high and low body condition scores or mixed groups of Cline, H. J., B. W. Neville, G. P. Lardy, and J. S. Caton. 2009. Influence cows and heifers) while being managed in common pastures. of advancing season on dietary composition, intake, site of diges- Furthermore, the CowManager system was able to detect di- tion, and microbial efficiency in beef steers grazing a native range vergence in highly active behavior but also reported many in western North Dakota. J. Anim. Sci. 87:375–383. doi:10.2527/ false health and estrus-related alerts. Technological solutions jas.2007-0833 must be made that incorporate algorithms developed using Cockwill, C. L., T. A. McAllister, M. E. Olson, D. N. Milligan, B. J. training sets originating from pasture-based beef cattle for Ralston, C. Huisma, and R. K. Hand. 2000. 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Journal

Translational Animal ScienceOxford University Press

Published: Jan 28, 2023

Keywords: activity monitoring; beef cattle; electronic feeder; mineral; supplement; grazing

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