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/lp/oxford-university-press/increased-lysine-metabolizable-energy-ratio-improves-grower-pig-GPdqYoZkN4
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- © The Author(s) 2018. Published by Oxford University Press on behalf of the American Society of Animal Science.
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- 2573-2102
- DOI
- 10.1093/tas/txy108
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Abstract
Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Increased lysine: metabolizable energy ratio improves grower pig performance dur- ing a porcine reproductive and respiratory syndrome virus challenge † † † † Wesley P. Schweer,* Omarh F. Mendoza, Caleb M. Shull, James Lehman, Aaron M. Gaines, ,‡ § ,1 Kent J. Schwartz, and Nicholas K. Gabler* *Department of Animal Science, Iowa State University, Ames, IA 50011; The Maschhoffs, LLC, Carlyle, IL ‡ § 62231; Ani-Tek Group, LLC, Shelbina, MO 63468; and Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA 50011 ABSTRACT: Porcine reproductive and respiratory syn- Exp. 1, increasing Lys:ME increased ADG (quadratic drome virus (PRRSV) reduces grower pig performance. P = 0.01) and G:F (linear and quadratic P = 0.04) in The amino acid (AA) requirements and lysine:metabo- control pigs over 35 d. In PRRSV-infected pigs, ADG lizable energy ratio (Lys:ME) of health-challenged pigs and G:F increased linearly with increasing Lys:ME for optimum performance are poorly understood. Two (P < 0.01). The Lys:ME for optimum ADG and G:F experiments were conducted to evaluate the effect of during PRRSV challenge was 2.83 and 3.17, respec- increasing standardized ileal digestible (SID) Lys:ME (g tively, compared to 2.24 and 2.83, respectively, in con- SID Lys per Mcal ME) on growth performance during trol pigs using a one-slope broken-line model. In Exp. 2, a PRRSV challenge. In Exp. 1, a total of 379 barrows pigs in the control barn became naturally infected after (51.3 ± 0.3 kg body weight [BW]) were allotted to one of 21 days post inoculation. Before infection, ADG and six diets (1.87 to 3.41 Lys:ME) for a 35-d growth study. G:F increased with increasing Lys:ME in control and In Exp. 2, a total of 389 barrows (29.2 ± 0.23 kg BW) PRRSV-infected pigs (linear and quadratic P < 0.05), were allotted to one of six diets (2.39 to 3.91 Lys:ME) for and optimum ADG and G:F were achieved at 3.02 and a 49-d growth study. These isocaloric diets represented 2.92 Lys:ME, respectively, in PRRSV-infected pigs com- 80% to 130% of National Research Council (NRC) pared to 2.82 and 3.22 Lys:ME, respectively, in control SID Lys requirement. For each experiment, pigs were pigs. Over the 49-d period, increasing Lys:ME improved randomly allotted across two barns of 24 pens each ADG (P < 0.01, linear and quadratic) and G:F (linear with seven to nine pigs per pen (four pens per diet per P < 0.01) in naturally infected pigs. The response was health status). On day 0, one barn was inoculated with similar in experimental infection for ADG (P < 0.01, lin- live PRRSV, one barn sham inoculated (control), and ear and quadratic) and G:F (linear P = 0.01). The opti- all pigs were started on experimental diets. Pen growth mum ratio for ADG (2.86 vs. 3.12 Lys:ME) and G:F performance and feed intake were recorded weekly and (3.18 vs. 3.08 Lys:ME) were similar between natural and gain-to-feed ratio (G:F) was calculated. Breakpoint experimental infection. In summary, increasing Lys:ME analysis was used to determine the Lys:ME that max- by 10% to 20% above NRC requirements improved per- imized average daily gain (ADG) and G:F over the 35 formance and feed efficiency during an experimental or 49-d test periods for Exp. 1 and 2, respectively. In and natural PRRSV challenge. Key words: lysine, metabolizable energy, pig, performance, porcine reproductive and respiratory syndrome virus © The Author(s) 2018. 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 Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com. Transl. Anim. Sci. 2018.XX:XX–XX doi: 10.1093/tas/txy108 Corresponding author: ngabler@iastate.edu Received June 8, 2018. Accepted September 28, 2018. 1 Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 INTRODUCTION Animal Care and Use Committee (IACUC# 8-16- 8330-S). This work was conducted between January Nutritional requirements have been well estab- and November 2017 in Ames, IA. lished for healthy pigs; however, requirements for Two experiments were conducted to deter- pigs facing health challenges are largely unexplored, mine the ideal SID Lys:ME for grow-finish bar - particularly amino acid (AA) requirements and rows (purebred Maschhoffs proprietary line these requirements in relation to energy intakes. It Duroc sires by commercial Yorkshire–Landrace has been established that pig performance and lean F1 females) during a PRRSV challenge. In both tissue accretion rates are decreased due to different experiments, pigs were split across two identi- pathogens (Escobar et al., 2004; Curry et al., 2017; cal barns with identical ventilation systems and Schweer et al., 2017; Helm et al., 2018); however, temperature set points. The two barns used were it is not known if this is a result of decreased feed approximately 15.2 m apart, contained two rooms intake. In addition, this may be due to a repartition- each, and each room had 12 large pens plus 2 ing of nutrients, specifically AA, to meet altered spare pens. Each pen contained a double-sided metabolic and immune needs (Klasing and Calvert, feeder and two nipple drinkers. In each pen, pigs 1999). Lysine is the first limiting AA for healthy had greater that 0.9 m per pig floor space. All pigs fed corn–soybean meal diets; however, AA per- test pen floor spaces, feeders, and waterers in each tinent to the immune system and its activation may room were identical. One barn was maintained differ from that of growth (Reeds et al., 1994; Le as a PRRS-negative control and the other inoc- Floc’h et al., 2004). ulated with a live PRRSV isolate (open reading Interestingly, Lys requirements (g per day frame [ORF] 5 sequence 1-18-4; Schweer et al. basis) are reduced in immune-stimulated pigs 2017). Pigs in the PRRSV barn were inoculated compared to control pigs (Williams et al., 1997b, on days post inoculation (dpi) 0 with 2 mL of live 1997c). This is due to a greater capacity for pro- PRRSV (1 mL intramuscular and 1 mL intrana- teinaceous tissue accretion in healthy pigs as par- sal; 10 genomic PRRSV units per mL) whereas tial efficiency for Lys utilization may not be altered the control barn received a sham saline inocu- due to health status (Williams et al., 1997a). In lation. Pigs were allowed unrestricted access to addition, adequate energy is essential for a proper feed and water. During the challenge period, immune response. Diets deficient in protein and pigs were fed one of six experimental diets; body energy can lead to reduced growth during parasite weight (BW) and feed disappearance were meas- (Trichuris suis also known as whipworm) infection ured weekly to determine average daily gain (Pedersen et al., 2002). (ADG), average daily feed intake (ADFI), and Porcine reproductive and respiratory syn- to calculate feed efficiency. Experimental diets drome virus (PRRSV) is one of the most eco- (Tables 1 and 2) were corn–soybean meal based nomically significant pathogens to the swine and were formulated to be isocaloric (ME basis) industry. However, research pertaining to this and meet or exceed the nutritional requirements virus’s impact on nutritional requirements in of 50 to 100 kg and 25 to 50 kg pigs in Exp. 1 pigs is minimal. Our group has recently reported and 2, respectively (NRC, 2012). There was a in growing pigs that PRRSV reduces lean tissue stepwise increase in SID Lys:ME and minimum accretion rates (Schweer et al., 2017), but basal ratios of SID Thr, Trp, Met, Ile, and Val to SID endogenous losses of many AA and standardized Lys were maintained. The dietary SID Lys:ME ileal digestibilities (SID) of AA are not different levels were achieved by increasing soybean meal (Schweer et al., 2018). Therefore, the objective of and l -Lys·hydrochloride (HCl). By design, as these studies was to evaluate the effects of graded Lys:ME increased so did crude protein (CP), but levels of g SID Lys per Mcal ME (lysine:metabo- the essential AA to Lys ratios were maintained lizable energy ratio [Lys:ME]) on pig performance using crystalline AA. The diet was formulated during a health challenge in the growing phase. so a majority of the SID Lys requirement was This will allow for the optimal Lys:ME to be met with soybean meal to maintain commercial defined for PRRSV-challenged pigs. relevance. These diets correlated to 80%, 90%, 100%, 110%, 120%, and 130% of NRC (2012) Lys MATERIALS AND METHODS requirement that has been previously validated All procedures adhered to the ethical and internally within the Maschhoffs production sys- humane use of animals for research and were tem for 50 to 100 kg and 25 to 50 kg pigs used in approved by the Iowa State University Institutional Exp. 1 and 2, respectively. Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Table 1. Experiment 1 diet composition, as fed basis SID Lys:ME, g/Mcal Ingredients, % 1.87 2.18 2.49 2.80 3.11 3.41 Corn 87.16 84.13 81.07 77.74 73.95 70.29 Soybean meal, 48% 9.75 12.75 15.74 19.10 22.92 26.61 Limestone 1.00 1.01 1.02 1.02 1.02 1.03 Monocalcium phosphate, 21% 1.13 1.07 1.05 0.94 0.86 0.79 Salt 0.51 0.51 0.51 0.51 0.51 0.51 l -Lysine·HCl 0.27 0.31 0.34 0.37 0.38 0.39 Commercial VTM 0.11 0.11 0.11 0.11 0.11 0.11 l -Threonine 0.05 0.06 0.08 0.10 0.10 0.11 dl -Methionine 0.02 0.05 0.08 0.11 0.13 0.15 Optiphos 1000 — — — 0.004 0.006 0.009 Calculated composition DM, % 85.6 85.7 85.8 85.9 86.0 86.1 CP, % 11.4 12.6 13.9 15.2 16.8 18.3 ME, Mcal/kg 3.28 3.27 3.27 3.27 3.27 3.26 Total calcium, % 0.65 0.65 0.66 0.65 0.65 0.65 STTD phosphorus, % 0.32 0.32 0.32 0.31 0.30 0.31 SID AA Lys 0.61 0.71 0.81 0.92 1.02 1.11 Thr:Lys 0.60 0.60 0.60 0.60 0.60 0.60 Met:Lys 0.30 0.32 0.33 0.34 0.35 0.35 Met+Cys:Lys 0.57 0.57 0.57 0.57 0.57 0.57 Trp:Lys 0.16 0.16 0.16 0.16 0.17 0.17 Ile:Lys 0.58 0.58 0.57 0.57 0.58 0.59 Val:Lys 0.71 0.68 0.66 0.65 0.65 0.65 SID Lys:ME, g/Mcal 1.87 2.18 2.49 2.80 3.11 3.41 Total Lys, % 0.70 0.80 0.91 1.02 1.13 1.23 Analyzed composition DM, % 85.8 85.8 85.9 87.3 87.1 87.0 GE (Mcal) 3.75 3.82 3.80 3.86 3.87 3.88 CP, % 13.6 15.3 16.3 18.4 20.3 22.8 Total AA:Lys Thr:Lys 0.61 0.63 0.61 0.62 0.67 0.59 Met:Lys 0.28 0.29 0.29 0.31 0.33 0.28 Met+Cys:Lys 0.58 0.58 0.55 0.57 0.59 0.50 Trp:Lys 0.15 0.16 0.16 0.16 0.19 0.17 Ile:Lys 0.57 0.56 0.64 0.65 0.68 0.56 Val:Lys 0.71 0.68 0.72 0.72 0.74 0.63 Lys, total % 0.76 0.87 0.96 1.04 1.14 1.27 VTM = Vitamin-trace mineral premix, which supplied per kilogram of diet: vitamin A, 8,820 IU; vitamin D , 1,653 IU; vitamin E, 33.1 IU; vitamin K, 4.4 mg; riboflavin, 6.6 mg; niacin, 38.9 mg; pantothenic acid, 22.1 mg; vitamin B , 0.04 mg; I, 1.1 mg as potassium iodide; Se, 0.30 mg sodium selenite; Zn, 60.6 mg as zinc oxide; Fe, 36.4 mg as ferrous sulfate; Mn, 12.1 mg as manganous oxide; and Cu, 3.6 mg as copper sulfate. STTD = standardized total tract digestible. Experiment 1, 50 to 100 kg BW pigs a 14-d acclimation period during which all pigs were fed a common diet. At the time of PRRSV In Exp. 1, a total of 379 barrows (51.3 ± 0.32 kg inoculation, pigs were started on experimental BW) were randomly allotted to one of six dietary diets (Table 1), and performance was measured for treatments with four pens per treatment per health 35 d. Diets were formulated to contain 1.87, 2.18, status and 7 to 8 pigs per pen. Before arrival, all pigs 2.49, 2.80, 3.11, and 3.41 SID Lys:ME, represent- were vaccinated for Mycoplasma hyopneumoniae, ing 80%, 90%, 100%, 110%, 120%, and 130% of porcine circovirus, erysipelas, and ileitis, and were National Research Council (NRC) requirement, serologically negative for PRRSV as determined by respectively. Weekly after PRRSV inoculation, the polymerase chain reaction (PCR). Pigs were given Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Table 2. Experiment 2 diet composition, as fed basis SID Lys:ME, g/Mcal Ingredients, % 2.33 2.63 2.94 3.24 3.55 3.85 Corn 82.16 79.11 75.59 71.87 68.02 64.29 Soybean meal, 48% CP 14.55 17.52 21.08 24.84 28.73 32.49 Limestone 0.96 0.98 0.98 0.99 0.99 1.00 Monocalcium phosphate, 21% 1.01 0.99 0.89 0.80 0.72 0.64 Salt 0.51 0.51 0.51 0.51 0.51 0.51 l -Lysine·HCl 0.32 0.35 0.37 0.38 0.39 0.40 Beef tallow 0.25 0.25 0.25 0.25 0.25 0.25 Commercial VTM 0.11 0.11 0.11 0.11 0.11 0.11 l -Threonine 0.07 0.09 0.10 0.10 0.11 0.12 dl -Methionine 0.06 0.09 0.12 0.14 0.16 0.18 Optiphos 1000 0.00 0.00 0.008 0.008 0.009 0.012 Calculated composition DM, % 86.2 86.3 86.3 86.4 86.5 86.6 CP, % 13.0 14.2 15.6 17.2 18.7 20.2 ME, Mcal/kg 3.29 3.29 3.29 3.29 3.29 3.29 Total calcium, % 0.63 0.64 0.63 0.63 0.63 0.63 STTD phosphorus, % 0.31 0.31 0.30 0.30 0.29 0.28 SID AA Lys 0.77 0.86 0.97 1.07 1.17 1.27 Thr:Lys 0.60 0.60 0.60 0.60 0.60 0.60 Met:Lys 0.32 0.33 0.34 0.34 0.35 0.35 Met+Cys:Lys 0.57 0.57 0.57 0.57 0.57 0.57 Trp:Lys 0.16 0.16 0.16 0.17 0.17 0.17 Ile:Lys 0.58 0.58 0.58 0.59 0.59 0.60 Val:Lys 0.67 0.66 0.65 0.65 0.65 0.65 SID Lys:ME, g/Mcal 2.33 2.63 2.94 3.24 3.55 3.85 Lys, total % 0.86 0.97 1.08 1.18 1.29 1.40 Analyzed composition DM, % 86.3 86.1 86.5 86.6 86.5 86.8 GE, Mcal/kg 3.73 3.80 3.81 3.84 3.86 3.84 CP, % 14.1 15.7 16.1 17.9 20.2 20.8 Total AA:Lys Thr:Lys 0.57 0.61 0.64 0.61 0.62 0.61 Met:Lys 0.26 0.31 0.32 0.32 0.30 0.30 Met+Cys:Lys 0.49 0.57 0.56 0.55 0.53 0.53 Trp:Lys 0.15 0.18 0.18 0.17 0.18 0.17 Ile:Lys 0.53 0.64 0.64 0.59 0.61 0.62 Val:Lys 0.63 0.71 0.70 0.64 0.66 0.66 Lys, total % 1.00 1.00 1.07 1.21 1.38 1.44 VTM=Vitamin-trace mineral premix, which supplied per kilogram of diet: vitamin A, 8,820 IU; vitamin D , 1,653 IU; vitamin E, 33.1 IU; vitamin K, 4.4 mg; riboflavin, 6.6 mg; niacin, 38.9 mg; pantothenic acid, 22.1 mg; vitamin B , 0.04 mg; I, 1.1 mg as potassium iodide; Se, 0.30 mg sodium selenite; Zn, 60.6 mg as zinc oxide; Fe, 36.4 mg as ferrous sulfate; Mn, 12.1 mg as manganous oxide; and Cu, 3.6 mg as copper sulfate. STTD = standardized total tract digestible. same two pigs per pen were bled for PRRSV PCR on BW. Shipping and pre-slaughter handling were and enzyme-linked immunosorbent assay (ELISA). the same for control and PRRSV-infected pigs. After the experimental period, all pigs were fed a common multiphase diet that met or exceeded NRC Experiment 2, 25 to 50 kg BW pigs (2012) requirements until pigs reached market BW (approximately 128 kg BW), at which time pigs In Exp. 2, a total of 389 barrows (29.2 ± 0.23 kg were slaughtered, and carcass data collected from BW) were vaccinated for M. hyopneumoniae, por- the slaughter plant (JBS, Marshalltown, IA). Pigs cine circovirus, erysipelas, and ileitis before arrival, were shipped for slaughter in two groups approxi- and serologically negative for PRRSV as deter- mately 5 d apart and these two groups were based mined by PCR. Barrows were randomly allotted to Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 one of six dietary treatments formulated to contain MA) and a commercial ELISA kit (HerdCheck 2.33, 2.63, 2.94, 3.24, 3.55, and 3.85 SID Lys:ME, PRRS X3; IDEXX Laboratories, Inc, Westbrook, representing 80%, 90%, 100%, 110%, 120%, and ME), respectively. 130% of NRC requirement, respectively (Table 2). Each treatment had four pens per treatment per Statistics health status with seven to nine pigs per pen. After Data within health status were analyzed using a 10-d acclimation on a common diet, pigs were the PROC MIXED procedure of SAS (SAS inoculated with PRRSV and started on experimen- Institute Inc, Cary, NC) for linear and quadratic tal diets for a 49-d growth study. Between 21 and effects of increasing SID Lys:ME. Pen served as the 28 dpi, the control barn became naturally infected experimental unit in both experiments. Data were with PRRSV and were confirmed positive by serum considered significant if P ≤ 0.05 and a trend if P PCR. The PRRSV strain isolated from the control ≤ 0.10. For all experiments, both one-slope straight barn was considered identical to the challenge iso- broken-line and quadratic broken-line analysis was late used in the PRRS barn by ORF-5 sequence. conducted as described by Robbins et al. (2006) to After the experimental period, all pigs were fed a estimate SID Lys:ME requirement for ADG and common multiphase diet that met or exceeded NRC G:F of each health status (control or PRRS pigs). (2012) requirements until pigs reached market BW In Exp. 1, breakpoint analysis was performed on (approximately 130 kg BW). In Exp. 2, carcass data performance over the 35-d experimental period. were not obtained from the slaughter plant. In Exp. 2, breakpoint analysis was performed on performance from 0 to 21 dpi, the period for which Diet Analysis control pigs were negative for PRRSV. Further, Analysis of gross energy (GE) in experimen- breakpoint analysis was performed over the 49-d tal diets in both experiments was carried out using experimental period (Exp. 2) to determine if SID bomb calorimetry (Oxygen Bomb Calorimeter Lys:ME requirements are similar between pigs nat- 6200; Parr Instrument Company, Moline, IL). urally and experimentally infected with PRRSV. Dietary dry matter (DM) in both experiments was carried out in a commercial laboratory (Midwest RESULTS Labs, Omaha, NE). Dietary AA and nitrogen (N) analysis were conducted by Ajinomoto Heartland, Diet Analysis Inc (Eddyville, IA). AA and N analysis were per- Experimental diets were formulated to con- formed using method 994.12, 999.13, and 990.03 tain 1.87, 2.18, 2.49, 2.80, 3.11, and 3.41 and 2.33, according to AOAC (2007) methods, and CP was 2.63, 2.94, 3.24, 3.55, and 3.85 g SID Lys per Mcal calculated (N × 6.25). ME in Exp. 1 and 2, respectively (Tables 1 and 2, respectively). Proximate and AA analysis of the Blood Collection and Analysis diets determined that experimental diets were for- In both experiments, 8 to 10 mL blood samples mulated similarly to the calculated values. The ratio were collected from the jugular vein into serum of SID Thr, Met + Cys, Trp, Ile, and Val to SID Lys tubes (BD Vacutainer, Franklin Lakes, NJ) while remained the same across all diets. As expected, CP pigs were snare restrained. In Exp. 1, the same increased as soybean meal inclusion increased. two pigs per pen were bled weekly during the 35-d challenge period. In Exp. 2, six pigs per room (12 Breakpoint Analysis pigs per barn) were randomly selected and bled weekly during the 49-d challenge period. Serum To determine the optimal dietary Lys:ME for from these pigs was pooled within room after centri- control and PRRS-infected pigs, we analyzed and fugation. Serum was allowed to clot then separated reported data using both straight broken-line and by centrifugation (2,000 × g, 15 min at 4 °C), ali- quadratic broken-line models. Nonlinear regression quoted and submitted to the Iowa State University analysis showed that both models fit the data simi- Veterinary Diagnostic Laboratory. Real-time larly (based on the R values). We reported two mod- reverse transcription PCR (RT-PCR) and serum els as selection of a specific model can dramatically antibody testing for PRRSV was performed using affect the identification of the requirement (Robbins commercial reagents (VetMAX PRRSV NA and et al., 2006; Nemechek et al., 2011). Also noted by EU reagents; Thermo Fisher Scientific, Waltham, Robbins et al. (2006), in a curvilinear response the Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 intersection of a straight broken-line and quad- PRRSV antibody increased causing a main effect ratic regression curve may more accurately define a of dpi (P < 0.001). requirement that can alternatively be defined using Before feeding experimental diets and inoc- a quadratic broken-line model. This multiple-model ulation, growth performance and feed efficiency approach has been reported in evaluating lysine were not different in control or PRRSV-infected requirements of nursery pigs (Jones et al., 2014). pigs (Table 4). Over the 35-d test period, control pig ADG increased as SID Lys:ME increased (quadratic, P = 0.013). G:F increased (linear, Experiment 1 P = 0.039; quadratic, P = 0.037) as SID Lys:ME In Exp. 1, there were two mortalities in the con- increased. Feed intake was not different over the trol barn and three in the PRRS barn. Both pigs in 35-d test period in control pigs. In the post-chal- the control barn succumbed to hemorrhagic bowel lenge period, when all pigs were on a common syndrome. Two unthrifty pigs in the PRRS barn diet, there were no performance differences (P > were euthanized shortly after arrival, and the third 0.10, data not shown). Pig growth and feed intake was determined to expire from porcine dermatitis from 0 dpi to market (76-d period) were not dif- and nephropathy syndrome. There were no associa- ferent (P > 0.10); however, G:F increased up to tions between mortality and dietary treatment. 3.11 SID Lys:ME resulting in a significant quad- Before experimental inoculation with PRRSV ratic effect (P = 0.040). Over the 35-d period, in both experiments, all pigs were negative for PRRSV-infected pig ADG and G:F increased PRRSV and antibody. In Exp. 1, control pigs linearly with increasing SID Lys:ME (P = 0.001 remained negative for PRRSV and antibody and P = 0.002, respectively), and ADFI tended throughout the 35-d experimental diet period and to increase (linear, P = 0.068). Similar to control to market, as expected. No diet or diet × dpi inter- pigs, there was no difference after 35 dpi when all actions were detected for PRRSV PCR Ct value or pigs were on a common diet (data not shown). Log PRRSV genomic content (Table 3). Similarly, From inoculation to market (78 ± 2 d), ADG no differences were detected for PRRSV antibody increased linearly with increasing SID Lys:ME (P > 0.10). Expectedly, PRRSV Ct value and Log (P = 0.011); however, ADFI and G:F were not genomic content decreased over time whereas different (P > 0.10). Table 3. Effect of increasing SID Lys:ME on PRRS viremia and antibody, Exp. 1 SID Lys:ME, g/Mcal P value Parameter 1.87 2.18 2.49 2.80 3.11 3.41 SEM Diet dpi Diet × dpi PRRSV Ct value dpi 7 21.9 21.5 23.5 23.0 21.9 22.0 1.28 0.124 <0.001 0.951 dpi 14 32.8 27.3 30.0 31.4 28.8 32.3 dpi 21 33.7 32.7 33.7 33.9 32.7 33.3 dpi 28 37.0 34.2 37.0 36.8 36.6 36.5 dpi 35 37.0 35.5 35.5 37.0 36.2 37.0 Genomic PRRSV/mL dpi 7 7.33 7.30 6.99 7.01 7.34 7.31 0.71 0.407 <0.001 0.946 dpi 14 3.36 4.92 4.92 4.49 4.60 4.24 dpi 21 2.40 3.41 3.11 3.76 4.12 3.93 dpi 28 0.00 2.26 0.00 0.78 0.82 0.88 dpi 35 0.00 1.15 1.00 0.00 0.96 0.00 PRRSV S/P ratio dpi 7 0.07 0.15 0.04 0.04 0.09 0.04 0.12 0.929 <0.001 0.676 dpi 14 2.22 2.12 2.24 1.90 2.08 2.10 dpi 21 2.28 2.29 2.30 2.13 2.18 2.24 dpi 28 2.02 2.24 2.25 2.21 2.13 2.19 dpi 35 2.19 2.25 2.19 2.13 2.07 2.10 n = 4 pens per diet, 7–8 pigs per pen. Main effect of diet, day post inoculation (dpi) and diet × dpi interaction. Cycle threshold (Ct), Ct ≥ 37.0 denotes PRRS negative. Log transformation of PRRSV genomic content/mL. PRRS X3 antibody sample to positive (S/P) ratio, <0.40 denotes PRRS negative. Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Table 4. Effect of increasing SID Lys:ME on growth performance in healthy and PRRSV-infected growing pigs, Exp. 1 SID Lys:ME, g/Mcal P value2 Parameter 1.87 2.18 2.49 2.80 3.11 3.41 SEM Linear Quadratic Pre-challenge Control Start BW, kg 36.4 36.4 36.4 36.3 36.4 36.4 0.80 0.962 0.989 ADG, kg 1.02 0.94 0.97 1.01 0.93 1.00 0.03 0.832 0.383 ADFI, kg 1.82 1.79 1.81 1.78 1.75 1.87 0.05 0.893 0.260 G:F 0.558 0.525 0.535 0.570 0.533 0.540 0.013 0.784 0.933 PRRSV Start BW, kg 36.8 36.7 37.0 37.0 36.9 37.0 0.76 0.811 0.928 ADG, kg 1.03 0.99 1.05 1.08 1.08 1.01 0.03 0.372 0.148 ADFI, kg 1.88 1.71 1.86 1.88 1.88 1.86 0.04 0.278 0.669 G:F 0.548 0.578 0.565 0.575 0.570 0.548 0.015 0.922 0.110 Challenge Control Start BW, kg 50.6 49.6 50.0 50.5 49.4 50.4 1.09 0.914 0.675 ADG, kg 1.05 1.11 1.14 1.12 1.13 1.11 0.02 0.069 0.013 ADFI, kg 2.79 2.91 2.85 2.83 2.71 2.87 0.06 0.695 0.891 G:F 0.375 0.383 0.403 0.395 0.418 0.388 0.009 0.039 0.037 PRRSV Start BW, kg 52.2 51.6 52.7 53.3 52.9 52.2 0.89 0.563 0.454 ADG, kg 0.70 0.74 0.76 0.86 0.84 0.86 0.04 0.001 0.396 ADFI, kg 2.05 1.99 2.16 2.13 2.12 2.13 0.05 0.068 0.374 G:F 0.343 0.370 0.353 0.408 0.395 0.403 0.014 0.002 0.536 Overall Control End BW, kg 128.0 130.2 131.5 130.9 130.4 130.4 2.04 0.481 0.336 ADG, kg 1.02 1.06 1.07 1.06 1.07 1.05 0.02 0.387 0.129 ADFI, kg 2.95 3.08 3.00 2.98 2.91 3.04 0.05 0.849 0.955 G:F 0.345 0.343 0.358 0.355 0.368 0.345 0.005 0.128 0.040 PRRSV End BW, kg 128.4 129.4 128.5 129.0 128.6 129.7 0.93 0.569 0.788 ADG, kg 0.95 0.97 0.98 0.98 0.99 1.02 0.02 0.011 0.841 ADFI, kg 2.40 2.34 2.46 2.45 2.42 2.47 0.06 0.240 0.964 G:F 0.398 0.415 0.398 0.398 0.410 0.413 0.010 0.500 0.643 n = 4 pens per diet, 7 to 8 pigs per pen. Linear and quadratic orthogonal contrast. Pre-challenge adaptation period (–14 to 0 dpi), all pigs on common diet. Challenge period (0 to 35 dpi), pigs fed experimental diets. Overall challenge period (0 dpi to market; control = 76 d, PRRS = 78 ± 2 d). Breakpoint analysis was used to determine ADG and G:F were predicted to be 3.71 and 4.22 the optimal SID Lys:ME to maximize growth and SID Lys:ME, respectively; however, these values feed efficiency in control and PRRSV-infected pigs are outside of the maximum SID 3.41 Lys:ME diet (Figure 1). It was determined that optimal ADG tested and should be studied further. in control pigs was achieved at 2.24 and 2.38 SID Carcass composition was evaluated when pigs Lys:ME using a one-slope and quadratic bro- reached approximately 128 kg BW (Table 5). All ken-line model, respectively. Optimal G:F was control pigs were marketed at 76 dpi, and there was achieved at 2.83 and 2.95 Lys:ME in a one-slope no difference in final BW (P > 0.10). There was a and quadratic broken-line model, respectively. In quadratic effect (P = 0.016) of SID Lys:ME on PRRSV-infected pigs, optimal ADG and G:F were fat depth where fat depth decreased from 1.87 to achieved at 2.83 and 3.17 SID Lys:ME, respec- 2.80 SID Lys:ME and increased from 2.80 to 3.41 tively, using a one-slope broken-line model. When SID Lys:ME. Concurrently, there was a linear ten- using a quadratic broken-line model, the optimal dency (P = 0.060) for lean percentage to increase Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 A) 1300 B) 1300 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal C) 0.50 D) 0.50 0.48 0.48 0.46 0.46 0.44 0.44 0.42 0.42 0.40 0.40 0.38 0.38 0.36 0.36 0.34 0.34 0.32 0.32 0.30 0.30 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal Figure 1. Data points represent treatments means from four pens per experimental diet per health status (Exp. 1). One-slope straight broken-line and quadratic broken-lines were fitted for maximum ADG (A and B) and G:F (C and D) expressed as a function of SID Lys:ME (g SID Lys per Mcal ME) over a 35-d growth period in control (A,C) and PRRSV (B,D) infected pigs, respectively. (A) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 2.24 g/Mcal (Y plateau = 1123.6 ADG; slope below requirement = −216.1; r = 0.38). The quadratic 2 2 broken-line model resulted in a SID Lys:ME requirement of 2.38 g/Mcal (Y = 1123.6 − 302.5(2.38 − g SID Lys/Mcal) ; r = 0.38). (B) The one- slope straight broken-line model yielded a SID Lys:ME requirement of 2.83 g/Mcal (Y plateau = 847.4 ADG; slope below requirement = −167.2; 2 2 r = 0.47). The quadratic broken-line model yielded a SID Lys:ME requirement of 3.71 g/Mcal (Y = 865.9 − 52.3(3.71 − g SID Lys/Mcal) ; r = 0.45); however, this predicted requirement is outside the range of the diets tested. (C) The one-slope straight broken-line model yielded a SID Lys:ME requirement of 2.83 g/Mcal (Y plateau = 0.401 G:F; slope below requirement = –0.026; r = 0.23). The quadratic broken-line model yielded 2 2 a SID Lys:ME requirement of 2.95 g/Mcal (Y = 0.400 – 0.023(2.95 – g SID Lys/Mcal) ; r = 0.25). (D) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 3.17 g/Mcal (Y plateau = 0.404 G:F; slope below requirement = −0.046; r = 0.41). The quadratic bro- 2 2 ken-line model projected a SID Lys:ME requirement of 4.22 g/Mcal (Y = 0.413 – 0.013(4.22 − g SID Lys/Mcal) ; r = 0.41); however, the predicted requirement is outside the range of the experimental diets. as SID Lys:ME increased. Hot carcass weight and infection, two due to gastric ulcers, one to rectal dress percentage were not impacted by increasing prolapse, and one to bacterial endocarditis. In both SID Lys:ME in control pigs. In PRRSV-infected barns, there were no treatment effects on mortality. pigs, fat depth increased linearly (P = 0.045), and Pigs responded more severely to PRRSV infection loin depth showed a strong tendency (P = 0.059) than anticipated, therefore to decrease the impact to decrease with increasing SID Lys:ME. Days to of opportunist bacteria and avoid a high num- market decreased from 80 to 77 d as SID Lys:ME ber of mortalities, antibiotics (Chlortetracycline; increased (linear, P = 0.004). PharmGate Animal Health, Omaha, NE) were delivered through the water for the entire barn from 11 to 14 dpi. Experiment 2 As there were no differences in PRRS viremia or The control and PRRS barn experienced three antibody attributed to diet in Exp. 1, pigs in Exp. 2 and nine mortalities, respectively. Two mortalities were randomly bled across diets to confirm PRRSV in the control barn were a result of porcine derma- infection status in control pigs (Table 6). In Exp. 2, titis and nephropathy syndrome and one from hem- control pigs remained PRRSV negative until 21 dpi; orrhagic bowel syndrome. In the PRRS barn, five however, after 21 dpi, the control pigs were natu- mortalities were a result of secondary respiratory rally infected with the same PRRSV isolate used for Translate basic science to industry innovation Gain:Feed ADG, g/d ADG, g/d Gain:Feed Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Table 5. Effect of increasing SID Lys:ME on carcass characteristics in control and PRRSV-infected pigs, Exp. 1 SID Lys:ME, g/Mcal P value Parameter 1.87 2.18 2.49 2.80 3.11 3.41 SEM Linear Quadratic Control Live weight, kg 128.0 130.2 131.5 130.9 130.4 130.4 2.04 0.481 0.336 HCW , kg 97.2 100.4 99.9 97.0 98.7 97.9 1.41 0.722 0.405 Dress % 76.1 77.2 76.0 74.1 75.7 75.1 1.28 0.312 0.837 Lean % 53.4 52.0 54.1 54.9 54.2 53.7 0.79 0.205 0.355 Fat thickness, mm 20.76 20.36 20.13 18.38 20.12 20.98 0.58 0.782 0.016 Loin depth, mm 60.19 61.05 62.96 60.31 63.60 63.35 1.24 0.060 0.994 Days to market 76 76 76 76 76 76 — — — PRRSV Live weight, kg 128.4 129.3 128.5 129.0 128.6 129.6 0.93 0.581 0.800 HCW , kg 97.4 94.7 98.0 96.5 97.7 96.8 1.72 0.755 0.975 Dress % 75.8 73.2 76.2 74.8 75.9 74.7 1.27 0.920 0.918 Lean % 52.5 54.9 54.0 53.7 53.1 53.3 0.96 0.867 0.272 Fat depth, mm 19.71 18.96 20.43 20.57 21.28 21.09 0.78 0.045 0.968 Loin depth, mm 64.70 63.48 63.09 61.91 60.46 60.93 1.72 0.059 0.791 Days to market 80 80 78 78 77 77 0.88 0.004 0.627 n = 4 pen per diet, 7 to 8 pigs per pen. Linear and quadratic orthogonal contrasts. HCW = hot carcass weight. All pigs marketed at 76 to 80 d after start of experimental diets and were fed a common control diet. determine the impact of a natural PRRSV infection Table 6. PRRS viremia and antibody of control compared to experimental infection. and PRRSV-infected pigs, Exp. 2 Before experimental infection at 0 dpi, control P value pig performance and feed efficiency were not differ - Parameter Control PRRSV SEM Diet dpi Diet × dpi ent (Table 7). During the first challenge period (0 PRRSV Ct value to 21 dpi) when control pigs were uninfected, ADG dpi 7 37.0 21.3 1.55 0.115 0.010 <0.001 (linear P < 0.001, quadratic P = 0.020) and G:F dpi 14 37.0 28.6 (linear P < 0.001) increased as Lys:ME increased. dpi 21 35.8 34.7 Feed intake increased from 2.33 to 3.24 Lys:ME dpi 28 24.1 36.2 and then decreased, resulting in a quadratic effect dpi 49 32.2 37.0 (P = 0.039). When breakpoint analysis was per- PRRSV S/P ratio formed on 0 to 21 dpi performance, optimal ADG dpi 7 0.00 0.87 0.18 <0.001 <0.001 0.005 dpi 14 0.00 1.54 and G:F was achieved at 2.82 and 3.22 Lys:ME, dpi 21 0.01 1.62 respectively, in a one-slope broken-line model dpi 28 0.19 1.74 (Figure 2). In a quadratic broken-line model, opti- dpi 49 1.78 1.75 mal ADG was attained at 3.32 Lys:ME. Optimal G:F was predicted at 4.22 Lys:ME; however, this n = 4 pens per diet, 7 to 8 pigs per pen. 2 was outside the range of the experimental diets Main effect of diet, day post inoculation (dpi) and diet × dpi interaction. tested. In PRRSV pigs, 21 d ADG, ADFI, and Cycle threshold (Ct), Ct ≥ 37.0 denotes PRRS negative. G:F increased linearly with increasing Lys:ME PRRS X3 antibody sample to positive (S/P) ratio, <0.40 denotes (P ≤ 0.001, all parameters), and ADG and G:F PRRS negative. also demonstrated a quadratic effect (P = 0.043 and P = 0.006, respectively). Breakpoint analysis experimental infection (ORF 5 sequence 1-18-4). The determined optimal ADG and G:F at 3.02 and control pigs became infected with PRRSV around 2.92, respectively, in a one-slope broken-line model 21 dpi, therefore, data were analyzed as two separate and 3.41 and 3.22, respectively, in a quadratic challenge periods. The first challenge period, 0 to 21 broken-line model. dpi, represents when control pigs were not infected In Exp. 2, control pigs became infected with with PRRSV. The second period, 0 to 49 dpi, is to PRRSV after 21 dpi. Therefore, performance Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 Table 7. Effect of increasing SID Lys:ME on growth performance in healthy and PRRSV-infected pigs and natural and experimental PRRSV infection, Exp. 2 SID Lys:ME, g/Mcal SEM P value Parameter 2.33 2.63 2.94 3.24 3.55 3.85 Linear Quadratic Pre-challenge Control Start BW, kg 23.0 23.1 23.1 22.9 22.8 22.4 0.46 0.299 0.396 ADG, kg 0.48 0.58 0.52 0.46 0.52 0.48 0.04 0.521 0.631 ADFI, kg 1.24 1.36 1.29 1.26 1.33 1.25 0.04 0.886 0.260 G:F 0.388 0.420 0.398 0.363 0.393 0.385 0.026 0.564 0.968 PRRSV Start BW, kg 23.3 23.5 23.7 23.9 23.5 22.9 0.57 0.684 0.248 ADG, kg 0.59 0.53 0.58 0.66 0.64 0.62 0.02 0.008 0.808 ADFI, kg 1.43 1.30 1.35 1.41 1.35 1.31 0.04 0.264 0.943 G:F 0.408 0.405 0.435 0.463 0.473 0.473 0.014 <0.001 0.600 Challenge 1 Control Start BW, kg 28.2 29.5 28.8 27.9 28.6 27.7 0.71 0.283 0.405 ADG, kg 0.65 0.81 0.87 0.92 0.92 0.92 0.05 <0.001 0.020 ADFI, kg 1.57 1.87 1.76 1.86 1.74 1.72 0.08 0.489 0.039 G:F 0.415 0.433 0.493 0.500 0.533 0.535 0.012 <0.001 0.123 PRRSV Start BW, kg 29.7 29.1 30.0 31.1 30.5 29.7 0.73 0.413 0.323 ADG, kg 0.19 0.26 0.43 0.45 0.39 0.49 0.04 <0.001 0.043 ADFI, kg 0.71 0.74 0.90 0.96 0.88 0.98 0.06 0.001 0.262 G:F 0.265 0.345 0.478 0.470 0.443 0.493 0.028 <0.001 0.006 Challenge 2 Natural infection ADG, kg 0.58 0.69 0.72 0.82 0.78 0.77 0.03 <0.001 0.003 ADFI, kg 1.49 1.66 1.61 1.79 1.68 1.63 0.06 0.086 0.029 G:F 0.390 0.418 0.443 0.460 0.463 0.473 0.013 <0.001 0.143 Experimental infection ADG, kg 0.55 0.58 0.72 0.78 0.73 0.75 0.03 <0.001 0.007 ADFI, kg 1.23 1.23 1.46 1.54 1.41 1.50 0.05 <0.001 0.037 G:F 0.445 0.468 0.495 0.503 0.515 0.500 0.018 0.011 0.147 Overall Control End BW, kg 116.2 130.2 123.4 130.7 131.5 125.2 2.49 0.016 0.006 ADG, kg 0.88 1.01 0.95 1.03 1.03 0.98 0.02 0.002 0.003 ADFI, kg 1.66 1.85 1.78 1.97 1.85 1.80 0.07 0.120 0.032 G:F 0.530 0.548 0.535 0.520 0.560 0.543 0.016 0.529 0.812 PRRSV End BW, kg 121.4 120.9 129.3 129.9 129.7 132.5 2.62 0.002 0.473 ADG, kg 0.90 0.90 0.97 0.97 0.97 1.01 0.02 0.001 0.712 ADFI, kg 1.44 1.41 1.66 1.72 1.61 1.69 0.05 <0.001 0.048 G:F 0.625 0.638 0.585 0.563 0.610 0.598 0.016 0.091 0.081 n = 4 pens per diet, 7 to 8 pigs per pen. Linear and quadratic orthogonal contrast. Pre-challenge adaptation period (–14 to 0 dpi), all pigs on common diet. Challenge period 1 (0 to 21 dpi), pigs fed experimental diets. Challenge period 2 (0 to 49 dpi), Control barn naturally infected with PRRSV after 21 dpi, pigs fed experimental diets. Overall challenge period (0 dpi to market); control pigs naturally infected after 21 dpi, PRRSV pigs experimentally infected at 0 dpi. and feed efficiency were evaluated from 0 to 49 with PRRSV, ADG increased linearly from dpi to determine the effect of natural vs. experi- 2.33 to 3.24 with increasing Lys:ME, resulting mental infection. In pigs naturally infected in both linear and quadratic effects (P < 0.001 Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 A) 1100 B) 1100 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal C) 0.58 0.58 D) 0.54 0.54 0.50 0.50 0.46 0.46 0.42 0.42 0.38 0.38 0.34 0.34 0.30 0.30 0.26 0.26 0.22 0.22 0.18 0.18 0.14 0.14 0.10 0.10 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal Figure 2. Data points represent treatment means from four pens per experimental diet per health status (Exp. 2). One-slope straight bro- ken-line and quadratic broken-lines were fitted for maximum ADG (A and B) and G:F (C and D) expressed as a function of standardized ileal digestible (SID) Lys:ME (g SID Lys per Mcal ME) over a 21-d growth period in control (A,C) and PRRSV (B,D) infected pigs, respectively. (A) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 2.82 g/Mcal (Y plateau = 908.8 ADG; slope below require- ment = −526.7; r = 0.59). The quadratic broken-line model resulted in a SID Lys:ME requirement of 3.32 g/Mcal (Y = 921.9 − 267.2(3.32 − g SID 2 2 Lys/Mcal) ; r = 0.61). (B) The one-slope straight broken-line model yielded a SID Lys:ME requirement of 3.02 g/Mcal (Y plateau = 442.2 ADG; slope below requirement = −387.3; r = 0.65). The quadratic broken-line model yielded a SID Lys:ME requirement of 3.41 g/Mcal (Y = 445.4 − 2 2 235.8(3.41 − g SID Lys/Mcal) ; r = 0.63). (C) The one-slope straight broken-line model yielded a SID Lys:ME requirement of 3.22 g/Mcal (Y plateau = 0.521 G:F; slope below requirement = −0.129; r = 0.74). The quadratic broken-line model yielded a SID Lys:ME requirement of 4.29 g/ 2 2 Mcal (Y = 0.544 – 0.036(4.29 – g SID Lys/Mcal) ; r = 0.78); however, this predicted value is outside the range of the experimental diets tested. (D) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 2.92 g/Mcal (Y plateau = 0.469 G:F; slope below require- ment = −0.361; r = 0.72). The quadratic broken-line model projected a SID Lys:ME requirement of 3.22 g/Mcal (Y = 0.472 – 0.272(3.22 − g SID 2 2 Lys/Mcal) ; r = 0.69). and P = 0.003, respectively). Also, in naturally Pigs experimentally infected with PRRSV infected pigs, ADFI increased quadratically demonstrated a similar response to increasing (P = 0.029) with a peak at 3.24 Lys:ME and Lys:ME, with ADG and ADFI having a lin- G:F increased linearly (P < 0.001) and with ear (P < 0.001, both parameters) and quadratic Lys:ME. From 0 dpi to market (approximately (P = 0.007 and P = 0.037, respectively) response, 100 d), ADG increased as Lys:ME increased, whereas G:F responded linearly to increasing causing an increase in final BW (linear P < 0.02, Lys:ME (P = 0.011). Overall, final BW and ADG quadratic P < 0.01, both parameters). Overall increased linearly with Lys:ME (linear P ≤ 0.002, feed intake increased in a quadratic manner both parameters). Feed intake increased from 2.33 (P = 0.032). Breakpoint analysis determined to 3.24 Lys:ME then decreased, leading to a lin- 2.85 and 3.41 Lys:ME for optimal ADG using ear (P < 0.001) and quadratic effect (P = 0.048). one-slope and quadratic broken-line models, Optimal ADG was achieved at 3.12 and 3.47 respectively (Figure 3). Optimal G:F Lys:ME Lys:ME using one-slope and quadratic broken-line was achieved at 3.18 and 3.85 in one-slope breakpoint analysis, respectively. Optimal G:F was and quadratic broken-line models, respectively achieved at 3.08 and 3.52 Lys:ME using one-slope (Figure 3). and quadratic broken-line models, respectively. Translate basic science to industry innovation ADG, g/d Gain:Feed ADG, g/d Gain:Feed Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 A) 1000 B) 500 500 400 400 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal C) 0.57 D) 0.57 0.55 0.55 0.53 0.53 0.51 0.51 0.49 0.49 0.47 0.47 0.45 0.45 0.43 0.43 0.41 0.41 0.39 0.39 0.37 0.37 0.35 0.35 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 SIDLys:ME, g/Mcal SIDLys:ME, g/Mcal Figure 3. Data points represent treatments means from four pens per experimental diet per health status (Exp. 2). One-slope straight broken-line and quadratic broken-lines were fitted for maximum ADG (A and B) and G:F (C and D) expressed as a function of standardized ileal digest- ible (SID) Lys:ME (g SID Lys per Mcal ME) over a 49-d growth period in pigs that experienced a natural (A,C) or experimental (B,D) PRRSV infection, respectively. (A) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 2.86 g/Mcal (Y plateau = 771.3 ADG; slope below requirement = −360.0; r = 0.62). The quadratic broken-line model resulted in a SID Lys:ME requirement of 3.41 g/Mcal 2 2 (Y = 784.4 – 176.4(3.41 − g SID Lys/Mcal) ; r = 0.67). (B) The one-slope straight broken-line model yielded a SID Lys:ME requirement of 3.12 g/ Mcal (Y plateau = 749.6 ADG; slope below requirement = −276.8; r = 0.71). The quadratic broken-line model yielded a SID Lys:ME requirement 2 2 of 3.47 g/Mcal (Y = 748.6 – 171.3(3.47 – g SID Lys/Mcal) ; r = 0.67); however, this predicted requirement is outside the range of the diets tested. (C) The one-slope straight broken-line model yielded a SID Lys:ME requirement of 3.18 g/Mcal (Y plateau = 0.466 G:F; slope below require- ment = –0.089; r = 0.64). The quadratic broken-line model yielded a SID Lys:ME requirement of 3.85 g/Mcal (Y = 0.471 – 0.036(3.85 – g SID Lys/ 2 2 Mcal) ; r = 0.65). (D) The one-slope straight broken-line model resulted in a SID Lys:ME requirement of 3.08 g/Mcal (Y plateau = 0.506 G:F; slope below requirement = −0.081; r = 0.36). The quadratic broken-line model projected a SID Lys:ME requirement of 3.52 g/Mcal (Y = 0.508 – 2 2 0.044(3.52 − g SID Lys/Mcal) ; r = 0.36). DISCUSSION improvement in feed efficiency when Met, Thr, and Trp were increased 20% relative to Lys. In contrast, In healthy growing pigs, Lys is the first limit- when immune system activation was modeled using ing AA for growth, and recommendations for Lys repeated lipopolysaccharides (LPS), Met+Cys requirements have been widely established (NRC, requirement was reduced (Rakhshandeh et al., 2012). Interestingly, when pigs are housed under 2014), but Met:Met+Cys requirement for protein unsanitary conditions, the Lys requirement for deposition increased (Litvak et al., 2013). These growth is reduced (Williams et al., 1997b, 1997c), data suggest that AA requirements in a model which has been attributed to a reduced capacity that mimics inflammation may be different from for protein accretion (Williams et al., 1997a); how- that of healthy pigs. Therefore, we conducted two ever, efficiency of Lys utilization may not be dif- experiments to determine how increasing Lys:ME ferent between healthy and immune-stimulated impacted growth performance in healthy and pigs. Therefore, reduced feed intake, and thus Lys PRRSV challenge pigs. intake, likely contributes to the reduction in lean To the best of our knowledge, this is the first set tissue accretion and growth. In a similar unsani- of experiments to determine the Lys:ME require- tary model, van der Meer et al. (2016) reported an ments for optimal ADG and G:F in pigs challenged Translate basic science to industry innovation ADG,g/d Gain:Feed ADG, g/d Gain:Feed Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 with PRRSV. Compared to healthy cohorts in is somewhat similar to results from Williams et al. Exp. 1, PRRSV increased Lys:ME requirement (1997b, 1997c) where growth was similar at simi- for ADG by 21% to 36% depending on the sta- lar Lys intake; however, these two studies used an tistical model used; however, the quadratic model unsanitary environment challenge model not a predicted Lys:ME requirement to be 3.71 Lys:ME live virus. In Exp. 2, 0 to 21 dpi ADG in control which is above the 3.41 Lys:ME tested in the study and PRRSV-infected pigs was maximized at 18.7 suggesting that the requirement could be higher and 10.6 g per day total Lys intake, respectively. than the test diets. Similarly, PRRSV increased the Control pigs had Lys intakes were close to the Lys:ME for optimal G:F by 11% to 30%. Similar predicted 16.9 g Lys per day intake recommended to the predicted quadratic requirement for ADG, by the NRC (2012) for 25 to 50 kg pigs. Although the G:F prediction was above the 3.41 Lys:ME PRRSV-infected pigs were well below NRC (2012) diet and, therefore, the requirement may be higher recommendation total Lys intake, PRRSV-infected than the tested diets. In Exp. 2, and in agreement pigs had Lys intakes close to the 12.8 g per day Lys with Exp. 1, optimal ADG was achieved at 3% to intake reported by Williams et al. (1997c) for opti- 7% higher Lys:ME in PRRSV-infected pigs com- mal growth in 25 kg pigs raised under immune-stim- pared to healthy controls. The PRRSV decreased ulated, unsanitary environmental conditions. Lys:ME requirement to achieve optimal G:F by 9% Infection appeared more severe in Exp. 2 as com- to 25%; however, optimal G:F in control pigs using pared to Exp. 1, likely because pigs were younger, a quadratic model predicted a requirement above therefore, more severe infection could result in Lys the diets tested. Because control pigs in Exp. 2 efficiency differences. became infected with PRRSV, the optimal Lys:ME When pigs are experimentally infected with a was able to be determined for natural vs. experi- pathogen, the population is on the same disease mental PRRSV infection. The optimal ADG and plane as opposed to a natural infection that can G:F was achieved at slightly higher Lys:ME levels lead to persistent, recurring infection (Yoon et al., in naturally infected pigs compared to experimen- 1999; Chand et al., 2012). Pigs that experienced nat- tally infected cohorts. These data contrast with the ural and experimental PRRSV infection reached a classic articles by Williams et al. (1997a, 1997b, similar peak viremia based on Ct values, and simi- 1997c) that show Lys requirements to be less in lar peak antibody. Naturally infected pigs appear to immune-stimulated pigs compared to healthy pigs; have experienced a shorter viremia duration; how- however, Lys efficiency was not different between ever, the same pigs were not bled for the duration groups, suggesting growth differences are related of the growth period to more accurately determine to feed intake and Lys intake. A similar response PRRSV and antibody dynamics. Pigs became nat- occurs in broilers challenged with LPS, where Lys urally infected around 45 kg, which likely allowed utilization by muscle does not change, but Lys them to cope better with disease. As mentioned, utilization by the immune system increases 6-fold pigs naturally and experimentally infected with (Klasing and Calvert, 1999). As mentioned pre- PRRSV had a similar Lys:ME for optimal growth. viously, soybean meal was used to increase diet- Therefore, it is difficult to elucidate the effect of ary Lys, therefore, intake of other AA are likely BW or diet on a potential protective role of against increased. Acute-phase protein synthesis requires a chronic PRRSV infection. large portion of aromatic AA (Reeds et al., 1994). In the U.S. swine industry, soybean meal is pri- Also, increased Met and Met + Cys can be bene- marily used to increase Lys and essential AA concen- ficial to protein deposition in LPS-challenged pigs trations in the diet. Feeding increased soybean meal (Litvak et al., 2013; Rakhshandeh et al., 2014). levels to PRRSV infected pigs may also have poten- Altogether, increased intake of these AA and oth- tial benefits for PRRS viral clearance (Rochell et al., ers can reduce the need for lean tissue catabolism 2015); however, Lys:ME was not different between and preserve lean tissue and therefore growth. diets. In the study presented herein, altering Lys:ME In Exp. 1, although ADG was different between by increasing soybean meal content of the diets did control and PRRSV-infected pigs, growth was opti- not alter viral titers, PRRSV genomic content or mized at total Lys intake of 22 and 21.5 g per day antibody response within the PRRSV-challenged for control and PRRSV-infected pigs, respec- pigs (Exp. 1). Although contrary to Rochell et al. tively, and both were close to the recommended (2015), this result is consistent with a previous study 20.5 g per day total Lys intake for 50 to 75 kg pigs from our group (Schweer et al., 2018). Increased by the NRC (2012). Although growth was differ- dietary soybean meal, regardless of Lys:ME can ent, it was optimized at similar Lys intake, which also increase performance in finishing pigs naturally Translate basic science to industry innovation Downloaded from https://academic.oup.com/tas/advance-article-abstract/doi/10.1093/tas/txy108/5128260 by guest on 16 October 2018 infected with PRRSV and porcine circoviral dis- pigs in Exp. 2, therefore, further studies should ease (Boyd et al., 2010). In 8 kg pigs infected with be conducted to more accurately determine the PRRSV, ADG was also improved in a soybean meal Lys:ME requirement. In Exp. 2, it was also deter- diet vs. a soybean meal plus crystalline AA diet with mined that Lys:ME for optimal ADG and G:F the same Lys:ME (Rochell et al., 2015). Although a between pigs naturally and experimentally infected linear increase in ADG and G:F has been reported in with PRRSV was not different. Altogether, increas- 55 kg pigs that were PRRSV positive at weaning as ing Lys:ME above the NRC requirement increased SID lysine increases (Shelton et al., 2011). In agree- performance and feed efficiency in PRRSV-infected ment with these reports, pigs infected with PRRSV pigs, and the response was similar between natural in this study showed linear improvements in ADG and experimental PRRSV infection. and G:F as Lys:ME increased. In agreement with Li et al. (2012), fat thick- ACKNOWLEDGMENTS ness was impacted by Lys:ME in control pigs. In This project was supported by the National this study, there was a clear quadratic effect while Pork Board, The Maschhoffs LLC, and by the Li et al. demonstrated both linear and quadratic Animal Health and Disease Research Capacity effects; however, in this study experimental diets Grant Program by State of Iowa funds from the were not fed up until carcass data were collected USDA National Institute of Food and Agriculture. as was the case in the study performed by Li et al. Conflict of interest statement. None declared. (2012). Interestingly, when comparing fat thick- ness in control and PRRSV-infected pigs, there LITERATURE CITED is an opposite effect of Lys:ME, where fat thick- AOAC. 2007. Official methods of analysis of AOAC interna- ness decreased from 1.87 to 2.80 Lys:ME in con- tional, 18th ed. Gaithersburg (MD): AOAC International. trol pigs and then increased up to 3.41 Lys:ME. In Boyd, R. D., M. E. Johnston, and C. E. Zier-Rush. 2010. 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Journal
Translational Animal Science – Oxford University Press
Published: Oct 12, 2018