Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Effects of reducing the standardized ileal digestible lysine and tryptophan to lysine ratio to slow growth of finishing pigs

Effects of reducing the standardized ileal digestible lysine and tryptophan to lysine ratio to... Translational Animal Science, 2022, 6, 1–7 https://doi.org/10.1093/tas/txac057 Advance access publication 6 May 2022 Non Ruminant Nutrition Effects of reducing the standardized ileal digestible lysine and tryptophan to lysine ratio to slow growth of finishing pigs † † †,1 †, Andres F. Tolosa, Mike D. Tokach, Robert D. Goodband, Jason C. Woodworth, † ‡, || Joel M. DeRouchey, Jordan T . Gebhardt, and Matt L. Wolfe Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506-0201, USA Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-0201, USA || Provimi North America, Brookville, OH 45309-8884, USA Corresponding author: goodband@ksu.edu ABSTRACT The COVID-19 global pandemic greatly affected pork processing plants in the United States. These pork processing plants were forced to ei- ther temporarily close or operate at reduced capacity due to the increased number of health-related employee absences. Because finishing pigs could not be timely marketed, methods to reduce growth performance were required to keep pigs from becoming too heavy at slaughter weight. Therefore, our objective was to determine the extent that reducing dietary standardized ileal digestible (SID) Lys and tryptophan-to- lysine ratio (Trp:Lys) ratio would slow finishing pig average daily gain (ADG) in a commercial setting. A total of 1,080 finishing pigs (327 × 1050, PIC; initially 32.3 kg) were used in a 119-d growth trial. Pigs were allotted by initial body weight (BW) and randomly assigned to 1 of 4 dietary treatments in a completely randomized block design with 27 pigs per pen and 10 pens per treatment. Three dietary regimes were formulated to contain either 100%, 90%, or 80% of the estimated SID Lys requirement for pigs in this facility, with a SID Trp:Lys ratio of 19%, with the excep- tion of the last dietary phase formulated to 17% SID Trp:Lys. Seven different dietary phases were fed. The SID Lys concentrations in the 100% diets were: 1.10%, 1.01%, 0.91%, 0.83%, 0.79%, 0.71%, or 0.67% SID Lys from 32 to 40, 40 to 51, 51 to 72, 72 to 85, 85 to 98, 98 to 112, and 112 to 130 kg, respectively. A fourth regime was formulated to 80% SID Lys with a SID Trp:Lys ratio of 16% (80–16% SID Trp:Lys) throughout all phases. Overall from d 0 to 119, ADG (linear, P < 0.001), final BW (linear, P < 0.001), and gain-to-feed (G:F) decreased (linear, P = 0.087) as SID Lys decreased from 100% to 80% of the estimated requirement. Pigs fed the 80–16% SID Trp:Lys diets had an additional decrease in ADG (P < 0.05) and G:F (P < 0.10) compared with pigs fed 80% of the SID Lys requirement with the normal Trp:Lys ratio. The reduction in SID Lys (from 100% to 80%) and reduction in SID Lys and Trp:Lys ratio resulted in an 8.6 and 11.7 kg, respectively, decrease in final BW compared with pigs fed Lys and Trp at the requirement (100%). This study provides alternatives for pork producers to reduce growth rate of finishing pigs. Key words: grow-finish pigs, lysine, slow down growth, tryptophan Abbreviations: ADG, average daily gain; ADFI, average daily feed intake; G:F, gain-to-feed; BW, body weight; SID, standardized ileal digestibility; Trp:Lys, tryptophan-to-lysine ratio; DDGS, distillers grains with solubles; STTD, standard total tract digestibility; COVID-19, coronavirus disease 2019 INTRODUCTION (Tokach et al., 2021). Therefore, pork producers were chal - lenged to find dietary strategies to decrease the growth rate In 2020, because of the COVID-19 global pandemic, pork of pigs. processing plants across the United States were either tem - Rao et al. (2021) and Helm et al. (2021) observed that porarily closed or had to decrease slaughter capacity due to pigs fed extremely low levels of Lys (all corn-based diets) the increased number of health-related employee absences. By had reduced ADG, gain-to-feed (G:F), and final body weight April 2020, one month after the United States government (BW). Soto et al. (2019) observed a 6.5% decrease in ADG issued a nationwide lockdown, processing plant capacity (i.e., as standardized ileal digestibility (SID) Lys decreased in the the level in which a processing plant uses its productive ca - diet from 0.75% to 0.45% in 100–125-kg pigs. In addition, pacity) decreased by 47% (USDA Agricultural Marketing altering the amino acid balance of the diet is another nutri - Service, 2020). As consequence, producers with pigs reaching tional strategy to investigate. Previous research has observed market weights were unable to access the processing plants that decreasing the ratio of Trp to Lys in the diet from 19% and had to find ways to reduce average daily gain (ADG) to 16% can reduce feed intake and decrease weight gain so pigs would not exceed packer upper weight limits which (Gonçalves et al., 2018). While there is considerable data would prevent harvesting. Swine producers have historically indicating the optimal nutrient fortifications to maximize aimed to improve growth rate and feed efficiency to decrease growth, there is limited data to examine nutrient alterations the time it takes for a pig to reach optimal marketing weight. to most efficiently slow growth rate and increase the amount The typical ADG during the finishing phase is between 800 of time needed to reach market weights in the event of a and 1,000 g/d with market weights of approximately 135 kg Received February 11, 2022 Accepted May 3, 2022. Published by Oxford University Press on behalf of the American Society of Animal Science 2022. This work is written by (a) US Government employee(s) and is in the public domain in the US. 2 Tolosa et al. processing plant or facility shutdowns. In response, this ex - MN). The barn was naturally ventilated and double-curtain- periment was conducted to determine the effect of reducing sided with a slatted concrete floor and deep manure storage. Lys and Trp on the growth performance of finishing pigs. Our Each pen (3.05 × 5.49 m) was equipped with a 5-hole stain - objective was to determine to what extent reducing the level less steel dry self-feeder (Thorp Equipment, Thorp, WI) and of SID Lys in diets for commercially raised grow-finish pigs a bowl waterer for ad libitum access to feed and water. The will decrease growth performance and to the extent that re - facility was equipped with a computerized feeding system ducing the tryptophan-to-lysine ratio (Trp:Lys) ratio would (FeedPro; Feedlogic Corp., Willmar, MN) that delivered and also decrease weight gain and slow down the growth of pigs recorded daily feed additions. The experiment was conducted in the finishing period. from June 19, 2020 to October 26, 2020. A total of 1,080 pigs (L337 × 1050, PIC; initially 32.0 kg) were used in a 119-d trial. Treatments were arranged in a MATERIALS AND METHODS randomized complete block design with 27 pigs per pen The Kansas State University Institutional Animal Care and and 10 pens per treatment. Initial pen weight served as Use Committee approved the protocol used in this study. the blocking factor. Dietary treatments were fed in seven phases and consisted of a control regimen (100% of the Animals and Diets estimated current SID Lys requirement curve for pigs in the The study was conducted at a commercial research-finishing New Horizon Farms production system) formulated to con - site in southwest Minnesota (New Horizon Farms, Pipestone, tain 1.10%, 1.01%, 0.91%, 0.83%, 0.79%, 0.71%, and Table 1. Composition of phases 1 and 2 experimental diets (as-fed basis) Phase 1 Phase 2 100 90 80 80%–16% Trp:Lys 100 90 80 80%–16% Trp:Lys Ingredient, % Corn 49.60 52.91 56.27 56.36 50.78 53.74 54.66 54.69 Soybean meal, 46.5% CP 7.51 4.25 0.93 0.87 3.86 0.79 – – DDGS 40.00 40.00 40.00 40.00 42.40 42.54 42.58 42.58 Limestone 1.39 1.42 1.44 1.44 1.42 1.44 1.45 1.45 Salt 0.46 0.46 0.46 0.46 0.45 0.45 0.45 0.45 l-Lys-HCl 0.68 0.65 0.63 0.63 0.67 0.65 0.55 0.55 dl-Met 0.05 0.02 – – 0.01 – – – l-Thr 0.12 0.10 0.09 0.08 0.11 0.10 0.05 0.05 l-Trp 0.07 0.07 0.07 0.04 0.08 0.07 0.06 0.04 Vitamin trace mineral premix 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Potassium chloride – – – – 0.10 0.10 0.10 0.10 Phytase 0.02 0.02 0.01 0.02 0.02 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 1.10 0.99 0.89 0.89 1.01 0.91 0.81 0.81 Ile:Lys 56 56 56 56 56 56 61 61 Met:Lys 31 30 30 30 30 30 33 33 Met and Cys:Lys 56 56 57 57 56 57 63 63 Thr:Lys 60 60 60 60 61 61 61 61 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 68 70 71 71 70 71 78 78 SID Lys:NE, g/Mcal 4.75 4.28 3.80 3.80 4.37 3.93 3.50 3.50 NE, kcal/kg 2,313 2,326 2,335 2,342 2,317 2,320 2,324 2,324 Ca, % 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 STTD P, % 0.36 0.35 0.32 0.34 0.36 0.33 0.33 0.33 Chemical analysis, % DM 86.98 87.12 87.58 87.25 87.36 87.68 87.40 86.99 CP 16.7 16.1 14.8 14.8 16.9 17.8 15.2 16.1 Experimental diets were fed for 2 and 4 weeks for phases 1 and 2, respectively. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 372–615 FTU per kg providing an estimated release ranging from 0.08 to 0.10 STTD P, %. DDGS, distillers grains with solubles; STTD, standard total tract digestibility. Dietary strategies to slow growth in pigs 3 0.67% SID Lys from 32 to 40, 40 to 51, 51 to 72, 72 to Statistical Analysis 85, 85 to 98, 98 to 112, and 112 to 130  kg, respectively. The pen was the experimental unit for all data. Response Two additional regimens contained 90% or 80% of the variables were analyzed using a general linear mixed model. SID Lys estimate. These three regimes were formulated to a Linear and quadratic contrasts were used to evaluate the ef - SID Trp:Lys ratio of 19% except for the last dietary phase fect of SID Lys reduction (treatments 100%, 90%, and 80%) which contained a 17% SID Trp:Lys ratio. The fourth reg- and a pairwise comparison was used to compare the 80% imen contained 80% of the SID Lys estimate with 16% SID SID Lys treatment with the 80%–16% SID Trp:Lys treat- Trp:Lys in all phases ( Tables 1–4). All diets were fed in meal ment. Heterogeneous residual variances as a function of the form and prepared at the New Horizon Farms feed mill response variables were fitted as needed. Model assumptions located in Pipestone, MN. were checked and considered to be appropriately met. The Pens of pigs were weighed, and feed disappearance was experimental data were analyzed using the lme4 package in measured approximately every 14 d throughout the exper - the R program (version 3.5.2, R Foundation for Statistical iment to determine ADG, average daily feed intake (ADFI), Computing, Vienna, Austria). Results were considered signifi - and G:F. In addition, pig removal, mortality, and evidence of cant at P ≤ 0.05 and a tendency at P ≤ 0.10. tail-biting were recorded. Two weeks before the end of the experiment, two pigs per pen were removed and marketed. RESULTS Later, final weights were obtained for the remaining pigs, and then they were marketed. No carcass data were collected be- For the overall period, ADG decreased (linear P, < 0.001), and a cause of restrictions to enter the processing plant due to the tendency (linear, P = 0.087) was observed for decreased G:F with ongoing outbreak of COVID-19. decreasing SID Lys (Table 5). The linear reduction in ADG was Table 2. Composition of phases 3 and 4 experimental diets (as-fed basis) Phase 3 Phase 4 100 90 80 80–16% Trp:Lys 100 90 80 80–16% Trp:Lys Ingredient, % Corn 53.65 54.75 54.95 54.98 61.42 62.41 62.63 62.65 Soybean meal, 46.5% CP 1.02 – – – 0.87 – – – DDGS 42.53 42.57 42.57 42.57 35.00 35.00 35.00 35.00 Limestone 1.31 1.32 1.32 1.32 1.26 1.27 1.27 1.27 Salt 0.45 0.45 0.45 0.45 0.49 0.49 0.45 0.45 l-Lys-HCl 0.65 0.57 0.45 0.45 0.58 0.51 0.40 0.40 l-Thr 0.11 0.07 0.01 0.01 0.10 0.07 0.01 0.01 l-Trp 0.07 0.06 0.05 0.02 0.07 0.06 0.04 0.02 Vitamin trace mineral premix 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Potassium chloride 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Phytase 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 0.91 0.82 0.73 0.73 0.83 0.74 0.66 0.66 Ile:Lys 56 60 68 68 56 60 67 67 Met:Lys 30 32 36 36 30 33 37 37 Met and Cys:Lys 56 61 69 69 58 63 70 70 Thr:Lys 62 62 62 62 63 63 63 63 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 71 76 86 86 72 77 87 87 SID Lys:NE, g/Mcal 3.95 3.56 3.16 3.16 3.51 3.16 2.81 2.81 NE, kcal/kg 2,315 2,320 2,320 2,320 2,366 2,357 2,359 2,359 Ca, % 0.53 0.53 0.53 0.53 0.51 0.51 0.51 0.51 STTD P, % 0.35 0.30 0.30 0.30 0.32 0.29 0.29 0.29 Chemical analysis, % DM 87.67 87.60 87.75 87.61 87.51 88.26 88.51 87.88 CP 17.9 16.3 16.0 16.1 18.15 15.9 16.4 16.2 Experimental diets were fed for 2 weeks. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 189–610 FTU per kg providing an estimated release ranging from 0.05 to 0.10 STTD P, %. 4 Tolosa et al. Table 3. Composition of phases 5 and 6 experimental diets (as-fed basis) Phase 5 Phase 6 100 90 80 80%–16% Trp:Lys 100 90 80 80%–16% Trp:Lys Ingredient, % Corn 65.90 67.52 67.69 67.71 67.51 67.66 67.80 67.82 Soybean meal, 46.5% CP 1.48 – – – – – – – DDGS 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 Limestone 1.20 1.21 1.21 1.21 1.16 1.16 1.16 1.16 Salt 0.52 0.45 0.45 0.45 0.45 0.45 0.45 0.45 l-Lys-HCl 0.53 0.49 0.39 0.38 0.49 0.40 0.31 0.31 l-Thr 0.10 0.07 0.02 0.02 0.08 0.04 – – l-Trp 0.06 0.05 0.04 0.02 0.06 0.04 0.03 0.01 Vitamin trace mineral premix 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Potassium chloride 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Phytase 0.02 0.01 0.01 0.02 0.01 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 0.79 0.71 0.63 0.63 0.71 0.64 0.57 0.57 Ile:Lys 56 58 65 66 58 64 72 72 Met:Lys 30 32 36 37 32 35 40 40 Met and Cys:Lys 58 61 69 70 61 68 76 76 Thr:Lys 63 63 63 63 64 64 65 65 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 72 75 85 85 75 83 94 94 SID Lys:NE, g/Mcal 3.31 2.98 2.65 2.65 2.98 2.69 2.39 2.39 NE, kcal/kg 2,381 2,381 2,381 2,392 2,381 2,381 2,381 2,381 Ca, % 0.49 0.49 0.49 0.49 0.47 0.47 0.47 0.47 STTD P, % 0.30 0.27 0.27 0.30 0.26 0.26 0.26 0.26 Chemical analysis, % DM 88.6 89.0 88.5 88.7 88.7 88.5 88.6 88.7 CP 15.7 15.5 15.1 15.4 13.4 13.1 13.4 14.3 Experimental diets were fed for 2 weeks. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 244–610 FTU per kg providing an estimated release ranging from 0.06 to 0.10 STTD P, %. found in all three reported phases (d 0–42, 42–84, and 84–119) pandemic. The increasing number of worker-related absences whereas the feed efficiency response was only significant from d resulted in a decrease in the utilization capacity of pork proc - 0 to 42. Pigs fed 90% and 80% of the estimated Lys requirement essing plants. Consequently, there was a major reduction in for these pigs were approximately 4.3 and 8.6 kg lighter than the number of pigs that could be processed daily ( Millet et pigs fed at their estimated requirement. There was no evidence of al., 2021; Hayes et al., 2021). Producers were faced with pigs treatment differences (P = 0.176) observed in ADFI. reaching market weights without the opportunity of being Within the 80% SID Lys treatments, overall ADG and BW slaughtered resulting in pigs above the processing plants’ were decreased (P < 0.05) when a further reduction of the SID weight limits. Pigs exceeding this upper weight limit have Trp:Lys ratio was applied. Pigs fed the lower SID Trp:Lys ratio virtually no economic value to the producer. Thus, swine diet were 3.1 kg lighter than the 80% SID Lys treatment and producers were forced to find alternatives to slow down 11.7 kg lighter in final BW compared with those fed 100% of growth so pigs can stay in the facilities until processing plants the Lys requirement estimate. For feed efficiency, pigs tended either re-opened or had the processing capacity to accept pigs (P < 0.10) to have decreased G:F when the lower SID Trp:Lys within the weight limit (Tokach et al., 2021). ratio was applied. There were no differences (P > 0.05) in pigs Management strategies such as increasing barn tempera- removed, total mortality, and incidences of tail-biting were not ture or reducing the floor space allowance per pig in the pen observed throughout the study (data not shown). (crowding) can result in reduced growth but also negatively affect animal welfare ( Gonyou et al., 2006). Therefore, the most practical and favorable alternative to slow growth, while DISCUSSION not impacting animal welfare, is to use dietary strategies that The year 2020 was tremendously challenging for the swine reduce protein deposition, and therefore, decrease growth industry supply chain due to the impact of the COVID-19 rate of the pig. Dietary strategies to slow growth in pigs 5 Table 4. Composition of phase 7 experimental diet (as-fed basis) these reductions resulted in a linearly decreased ADG and G:F. Similarly,Li et al. (2012) evaluated the performance of grow- Phase 7 finish pigs at three different body weight ranges (i.e., 29–47, 54–76, and 84–109 kg) and observed that pigs fed less SID Lys Ingredient, % 100 90 80 80–16% Trp:Lys had reduced ADG and a decrease in G:F compared with pigs Ingredient, % fed greater concentrations of SID Lys. Their study fed pigs a diet with SID Lys reduced by 19.8%, 11.6%, and 19.1% of Corn 78.90 81.16 82.74 82.75 the requirement estimate in the previously mentioned weight Soybean meal, 3.62 1.54 – – 46.5% CP ranges (0.77 vs. 0.96, 0.68 vs. 0.77, and 0.55 vs. 0.68% SID Lys). These reductions resulted in an 8.8%, 6.4%, or 10.2% DDGS 15.00 15.00 15.00 15.00 decrease in ADG and a 12.8%, 9.1%, or 7.7% decrease in Limestone 1.09 1.10 1.11 1.11 feed efficiency. For the pigs in the heavier weight range (84– Salt 0.60 0.45 0.45 0.45 109  kg) the 19.1% SID Lys reduction resulted in a 2.9  kg l-Lys-HCl 0.40 0.39 0.35 0.35 lower final body weight after 28 d, therefore, these pigs would l-Thr 0.09 0.08 0.06 0.06 need 3.6 extra days to reach a maximum BW of 109  kg. A l-Trp 0.03 0.03 0.03 0.02 more recent study by Soto et al. (2019) using pigs over 100 kg Vitamin trace 0.09 0.09 0.09 0.09 (102  ±  0.4  kg) fed pigs up to 27.4% less SID Lys than the mineral estimated requirement for maximum ADG and observed that premix there was a linear reduction in ADG of pigs. This body of lit - Potassium 0.10 0.10 0.10 0.10 erature helped set the stage when producers had to reduce the chloride growth of their pigs due to extensive supply chain disruptions Phytase 0.02 0.02 0.02 0.02 within the industry during the COVID-19 pandemic. Also, Lipinate 0.05 0.05 0.05 0.05 an additional repeatable consequence of reducing the dietary Calculated analysis SID Lys level below requirement was a worsening of feed effi- ciency that must be considered. SID AA, % Other dietary alternatives to slow down growth include Lys 0.67 0.61 0.54 0.54 increasing the dietary fiber content of the diet that conse - Ile:Lys 56 56 58 58 quently reduces nutrient digestibility and increases digesta Met:Lys 29 31 33 33 viscosity and volume (frequently associated with satiety) Met and Cys:Lys 57 60 65 65 (Kerr and Shurson, 2013; Helm et al., 2021 ). However, Helm Thr:Lys 65 65 65 65 et al. (2021) fed pigs 75–105  kg BW a diet with increased Trp:Lys 17.0 17.0 17.0 16.0 levels of neutral detergent fiber (NDF) from 9.5% to 25% Val:Lys 71 73 77 77 and observed a tendency for a decrease in weight gain during the initial 7 d of feeding with no impact thereafter. SID Lys:NE, 2.77 2.49 2.22 2.22 g/Mcal Within the same experiment, Helm et al. (2021) aimed to severely impact growth by decreasing indispensable amino NE, kcal/kg 2,439 2,452 2,459 2,459 acid concentrations in the diet by either replacing 50% of Ca, % 0.45 0.45 0.45 0.45 soybean meal and feed-grade amino acids with corn or by STTD P, % 0.25 0.25 0.24 0.24 feeding a 97% corn-based diet without soybean meal or Chemical analysis, % feed-grade amino acids. These diets resulted in a decrease DM 87.4 87.5 87.8 87.5 of 0.37% and 0.76% of SID Lys, respectively; however, the CP 14.0 13.7 13.6 13.6 SID Trp:Lys increased from 0.18% to 0.22% and 0.26%, respectively. This reduction in SID Lys resulted in a linear de - Experimental diets were fed for 2 weeks. crease in ADG of 17% and 59% and G:F of 16% and 60% Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg when pigs were fed diets with 0.48% and 0.18% SID Lys vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, compared with pigs fed 0.77% SID Lys, respectively, which and 11 µg vitamin B12. 3 is in agreement with results from the current experiment. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) provided at 615 FTU per kg with an estimated release of 0.10% available P. Rao et al. (2021) fed finishing pigs a diet with reduced SID Feed additive for animals used for managing carcass fat composition Lys where pigs in the control treatment were fed 0.70% SID (Nutriquest LLC, Mason City, IA). Lys and two additional diets were formulated at 0.50% and 0.18% SID Lys. They observed a 17.4% and 16.3% decrease Multiple amino acid titration studies aimed to estimate in ADG and a 14.9% and 15.2% reduction in G:F as SID Lys amino acid concentrations for optimal growth and efficiency was reduced in the diet from 0.70% to 0.50% and 0.18% of the pig have been conducted and help to understand that SID Lys, respectively. There was no impact on ADFI observed when essential or limiting amino acids, such as Lys and Trp, as SID Lys was reduced. were reduced, performance was impacted. Early studies by Furthermore, research has elucidated that an amino acid Hahn et al. (1995) illustrated that when Lys was fed below imbalance can result in detrimental effects on growth perfor - the requirement, daily gain and feed efficiency were affected mance. Reducing or increasing amino acids in the diet, can negatively. In their study,Hahn et al. (1995) determined that cause amino acid imbalances. Therefore, reducing the ratio the SID Lys requirement for barrows and gilts from 80 to of Leu, Val, or Trp in relation to Lys or increasing the sulfur 120  kg was 0.49 and 0.52%, respectively. The lowest level amino acids (SAA) to Lys ratio can consequently decrease the of SID Lys fed was 0.41%, which represented a reduction gain and overall growth of the pig ( Gonçalves et al., 2018 ; of 16.3% and 21.2% for barrows and gilts, respectively, and Cemin et al., 2019; Tokach et al., 2021). Edmonds and Smith 6 Tolosa et al. 1,2 Table 5. Effects of reducing SID Lys and SID Trp:Lys ratio on growth performance of grow-finish pigs 3 4 SID Lys, % P Item 100 90 80 80%–16% Trp:Lys SEM Linear Quadratic BW, kg d 0 32.3 32.4 32.4 32.3 0.87 0.507 0.630 a b d 42 66.4 65.0 62.4 60.0 1.13 0.001 0.185 c d d 84 102.2 99.2 96.0 93.5 1.28 0.001 0.947 a b d 119 134.0 129.7 125.4 122.3 1.40 0.001 0.999 d 0–42 a b ADG, kg 0.77 0.73 0.68 0.62 0.010 0.001 0.209 c d ADFI, kg 1.83 1.86 1.83 1.74 0.005 0.964 0.524 a b G:F 0.418 0.395 0.371 0.357 0.0591 0.001 0.869 d 42–84 ADG, kg 0.87 0.83 0.82 0.81 0.009 0.001 0.305 ADFI, kg 2.49 2.43 2.38 2.43 0.057 0.122 0.943 G:F 0.348 0.341 0.343 0.332 0.0943 0.752 0.66 d 84–119 ADG, kg 0.95 0.93 0.91 0.89 0.012 0.001 0.988 ADFI, kg 3.29 3.22 3.14 3.19 0.053 0.055 0.919 G:F 0.289 0.289 0.288 0.280 0.0692 0.887 0.969 Overall (d 0–119) a b ADG, kg 0.85 0.82 0.79 0.76 0.006 0.001 0.887 ADFI, kg 2.46 2.43 2.38 2.37 0.049 0.176 0.786 d c G:F 0.349 0.339 0.333 0.323 0.0550 0.087 0.862 A total of 1,080 pigs (initially 32.3 kg) were used with 27 pigs per pen and 10 replications per treatment. BW = body weight; ADG = average daily gain; ADFI = average daily feed intake; G:F = gain-to-feed ratio. Standardized ileal digestible (SID) Lys of the estimated requirement (100%, 90%, or 80%) or 80% with an additional reduction of SID Trp:Lys ratio to 16%. Treatments 100, 90 and 80 were fed 19% Trp:Lys ratio from 0 to 98d with the exception of the last phase were the ratio of Trp:Lys was 17%, from 98 to 119d. Linear and quadratic contrasts included treatments 100, 90 and 80. a,b Treatment: 80 vs. 80–16% Trp:Lys differ (P ≤ 0.05). c,d Treatment: 80 vs. 80–16% Trp:Lys differ (P ≤ 0.10). (2021) evaluated increasing the level of SAA by increasing the ADG and ADFI was observed for growing and finishing pigs level of feed-grade Met in the diet. Their diets resulted in an from 50 to 80 and 80 to 110 kg resulting in final BW being increased ratio of SID SAA:Lys from 3.87% to 5.05% on pigs reduced by 1.9 or 2.2 kg, respectively, which was explained from 109 to 144 kg. Increasing SID SAA:Lys ratio in the diet by a reduction in ADG and ADFI when fed 15% vs. 18% resulted in a significant reduction in ADG of 62% when pigs SID Trp:Lys ratio for both bodyweight ranges. Reducing SID were the fed highest level of SAA compared to pigs fed the Trp:Lys in a diet that is also deficient in Lys was observed to lowest SAA:Lys ratio. In addition, Trp is typically the second further decrease growth and resulted in a lighter pig compared limiting amino acid in corn-soybean meal-based diets and acts with pigs fed a diet with Lys at the requirement in the current as a precursor to important biological roles, such as the syn - experiment, which is in agreement with previous data (Salyer thesis of serotonin, which is associated with regulating stress, et al., 2013; Gonçalves et al., 2018 ; Liu et al., 2019). All in sleep, and appetite ( Le Floc’h and Seve, 2007 ). Therefore, re- all, this information illustrates the impact that amino acid ducing the level of Trp in relation to Lys in the diet can further imbalances in the diet have on the performance of grow-finish reduce growth by decreasing feed intake. Multiple studies pigs. Previous trials were carried out with small groups of have evaluated the response in performance of pigs fed a diet pigs and in university research facilities, therefore, data were formulated with varying ratios of Trp:Lys.Salyer et al. (2013) needed to evaluate the effect of reducing Lys and Trp to Lys noted that ADG, ADFI, and BW were negatively impacted if ratio on growth performance utilizing larger pig groups and pigs were fed less than 16.5 and 19.5% SID Trp:Lys from 36 commercial facilities. To the best of our knowledge, this is the to 73 and 66 to 124 kg of BW, respectively. This is consistent first study that has been carried out under field conditions with Gonçalves et al. (2018) that observed reducing Trp in the that evaluated the effect of reducing Lys and Trp:Lys ratio in diet from 19% to 16% of Lys resulted in reduced feed intake diets on the growth performance of finishing pigs and decreased weight gain, and therefore, reduced G:F. In a The current study showed that if producers fed 80% of the similar fashion, Liu et al. (2019) conducted two experiments SID Lys requirement to pigs starting at 32 kg, it would take evaluating various SID Trp:Lys ratios in a diet fed to pigs 10.9 more days to reach 134 kg which was the final weight from 50 to 80 and 80 to 110 kg, and it was estimated that of the pigs fed the diet formulated to meet the amino acid the optimal SID Trp:Lys ratio for maximum ADG was 18% requirements. In addition, if pigs were fed a diet with 80% for both bodyweight ranges. A quadratic reduction in both SID Lys and 16% SID Trp:Lys, it would take an additional Dietary strategies to slow growth in pigs 7 Hahn, J. D., R. R. Biehl, and D. H. Baker.1995. Ideal digestible lysine 4.5 days (a total of 15.4 days) to achieve the same weight. level for early- and late-finishing swine.J . Anim. Sci. 73:773–784. This dietary strategy would enable producers to provide doi:10.2527/1995.733773x. pigs more time in the barn avoiding becoming too heavy Hayes, D. J., L. L. Schulz, C. E. Hart, and K. L. Jacobs.2021. A descrip- and risking economic penalties or acceptance to processing tive analysis of the COVID-19 impacts on U.S. pork, turkey, and plants. egg markets. Agribusiness 37:122–141. doi: 10.1002/agr.21674. In conclusion, the COVID-19 pandemic forced pork Helm, E. T., J. F. Patience, M. R. Romoser, C. D. Johnson, J. W. Ross, and N. producers and nutritionists to evaluate situations that had K. Gabler. 2021. Evaluation of increased fiber, decreased amino acids, not been a priority of the industry in the past and that can be or decreased electrolyte balance as dietary approaches to slow finish - helpful in future scenarios, such as human disease pandemics ing pig growth rates. J. Anim. Sci. 7:1–9. doi:10.1093/jas/skab164. or supply chain disruptions This study presents useful in - Kerr, B. J., and G. C. Shurson. 2013. Strategies to improve fiber utili - zation in swine. J. Anim. Sci. Biotechnol. 4:11. doi:10.1186/2049- formation to producers regarding dietary changes to slow the 1891-4-11. growth of pigs during the grow-finish period. Le Floc’h, N., and B. Seve. 2007. Biological roles of tryptophan and its metabolism: Potential implications for pig feeding. Livest. Sci. 112(1–2):23–32. ACKNOWLEDGMENTS Li, P., Z. Z, W. D, X. L, R. Zhang, and P. X. 2012. Effects of the Contribution no. 22-231-J of the Kansas Agricultural standardized ileal digestible lysine to metabolizable energy ratio on Experiment Station, Manhattan, 66506-0201. We would like performance and carcass characteristics of growing-finishing pigs. to thank the staff of New Horizon Farms, Pipestone MN, for J. Anim. Sci. Biotechnol. 3:9. doi:10.1186/2049-1891-3-9. Liu, J. B., H. L. Yan, S. C. Cao, J. Liu, X. Z. Li, and H. F. Zhang. use of animals and technical support. 2019. The response of performance in grower and finisher pigs to diets formulated to different tryptophan to lysine ratios. Li v. Sci. 222:25–30. doi:10.1016/j.livsci.2019.01.016. Conflict of interest statement Millet, S., S. De Smet, E. F. Knol, B. G, P. Trevisi, S. Vigors, K. Nilsson, None declared. and J. Van Meensel. 2021. How two concurrent pandemics put a spoke in the wheel of intensive pig production. Anim. Frontiers 11:14–18. doi:10.1093/af/vfaa051. LITERATURE CITED Rao, Z., M. D. Tokach, J. C. Woodworth, J. M. DeRouchey, R. D. Goodband, Cemin, H. S., M. D. Tokach, S. S. Dritz, J. C. Woodworth, J. M. and J. T. Gebhardt. 2021. Evaluation of nutritional strategies to slow DeRouchey, and R. D. Goodband.2019. Meta-regression analysis growth rate then induce compensatory growth in 90-kg finishing pigs. to predict the influence of branched-chain and large neutral amino Transl. Anim. Sci 5:1–11. doi:10.1093/tas/txab037. acids on growth performance of pigs. J. Anim. Sci. 97:2505–2514. Salyer, J. A., M. D. Tokach, J. M. DeRouchey, S. S. Dritz, R. D. doi:10.1093/jas/skz118. Goodband, and J. L. Nelssen.2013. Effects of standardized ileal Edmonds, M. S., and J. W. Smith. 2021. Amino acid imbalance with digestible tryptophan:lysine in diets containing 30% dried distillers excess methionine in late-finishing pigs: effects on performance grains with solubles on finishing pig performance and carcass traits. and carcass quality. Trans. Anim. Sci 5:197. doi:10.1093/tas/ J. Anim. Sci. 91:3244–3252. doi:10.2527/jas.2012-5502. txab197. Soto, J. A., M. D. Tokach, S. S. Dritz, J. C. Woodworth, J. M. DeRouchey, Gonçalves, M. A. D., M. D. Tokach, N. M. Bello, K. J. Touchette, R. R. D. Goodband, and F. Wu. 2019. Optimal dietary standardized D. Goodband, J. M. DeRouchey, J. C. Woodworth, and S. S. Dritz. ileal digestible lysine and crude protein concentration for growth 2018. Dose–response evaluation of the standardized ileal digest - and carcass performance in finishing pigs weighing greater than ible tryptophan: lysine ratio to maximize growth performance 100 kg. J. Anim. Sci. 97:1701–1711. doi:10.1093/jas/skz052. of growing-finishing gilts under commercial conditions. Animal Tokach, M. D., B. D. Goodband, J. M. DeRouchey, J. C. Woodworth, 12:1380–1387. doi:10.1017/S1751731117002968. and J. T. Gebhardt. 2021. Slowing pig growth during COVID-19, Gonyou, H. W., M. C. Brumm, E. Bush, J. Deen, S. A. Edwards, T. models for use in future market fluctuations. Anim. Front. 11:23– Fangman, J. J. McGlone, M. Meunier-Salaun, R. B. Morrison, 27. doi:10.1093/af/vfaa047. H. Spoolder, et al. 2006. Application of broken-line analysis to USDA Agricultural Marketing Service 2020. National daily direct assess floor space requirements of nursery and grower-finisher hog prior day—slaughtered swine [accessed November 22, 2020]. pigs expressed on an allometric basis.J . Anim. Sci. 84:229–235. https://mpr.datamart.ams.usda.gov/menu.do?path=Products\Hogs\ doi:10.2527/2006.841229x. Daily%20Swine http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Translational Animal Science Oxford University Press

Effects of reducing the standardized ileal digestible lysine and tryptophan to lysine ratio to slow growth of finishing pigs

Loading next page...
 
/lp/oxford-university-press/effects-of-reducing-the-standardized-ileal-digestible-lysine-and-lIdJ2Chsdd
Copyright
Published by Oxford University Press on behalf of the American Society of Animal Science 2022.
eISSN
2573-2102
DOI
10.1093/tas/txac057
Publisher site
See Article on Publisher Site

Abstract

Translational Animal Science, 2022, 6, 1–7 https://doi.org/10.1093/tas/txac057 Advance access publication 6 May 2022 Non Ruminant Nutrition Effects of reducing the standardized ileal digestible lysine and tryptophan to lysine ratio to slow growth of finishing pigs † † †,1 †, Andres F. Tolosa, Mike D. Tokach, Robert D. Goodband, Jason C. Woodworth, † ‡, || Joel M. DeRouchey, Jordan T . Gebhardt, and Matt L. Wolfe Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506-0201, USA Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-0201, USA || Provimi North America, Brookville, OH 45309-8884, USA Corresponding author: goodband@ksu.edu ABSTRACT The COVID-19 global pandemic greatly affected pork processing plants in the United States. These pork processing plants were forced to ei- ther temporarily close or operate at reduced capacity due to the increased number of health-related employee absences. Because finishing pigs could not be timely marketed, methods to reduce growth performance were required to keep pigs from becoming too heavy at slaughter weight. Therefore, our objective was to determine the extent that reducing dietary standardized ileal digestible (SID) Lys and tryptophan-to- lysine ratio (Trp:Lys) ratio would slow finishing pig average daily gain (ADG) in a commercial setting. A total of 1,080 finishing pigs (327 × 1050, PIC; initially 32.3 kg) were used in a 119-d growth trial. Pigs were allotted by initial body weight (BW) and randomly assigned to 1 of 4 dietary treatments in a completely randomized block design with 27 pigs per pen and 10 pens per treatment. Three dietary regimes were formulated to contain either 100%, 90%, or 80% of the estimated SID Lys requirement for pigs in this facility, with a SID Trp:Lys ratio of 19%, with the excep- tion of the last dietary phase formulated to 17% SID Trp:Lys. Seven different dietary phases were fed. The SID Lys concentrations in the 100% diets were: 1.10%, 1.01%, 0.91%, 0.83%, 0.79%, 0.71%, or 0.67% SID Lys from 32 to 40, 40 to 51, 51 to 72, 72 to 85, 85 to 98, 98 to 112, and 112 to 130 kg, respectively. A fourth regime was formulated to 80% SID Lys with a SID Trp:Lys ratio of 16% (80–16% SID Trp:Lys) throughout all phases. Overall from d 0 to 119, ADG (linear, P < 0.001), final BW (linear, P < 0.001), and gain-to-feed (G:F) decreased (linear, P = 0.087) as SID Lys decreased from 100% to 80% of the estimated requirement. Pigs fed the 80–16% SID Trp:Lys diets had an additional decrease in ADG (P < 0.05) and G:F (P < 0.10) compared with pigs fed 80% of the SID Lys requirement with the normal Trp:Lys ratio. The reduction in SID Lys (from 100% to 80%) and reduction in SID Lys and Trp:Lys ratio resulted in an 8.6 and 11.7 kg, respectively, decrease in final BW compared with pigs fed Lys and Trp at the requirement (100%). This study provides alternatives for pork producers to reduce growth rate of finishing pigs. Key words: grow-finish pigs, lysine, slow down growth, tryptophan Abbreviations: ADG, average daily gain; ADFI, average daily feed intake; G:F, gain-to-feed; BW, body weight; SID, standardized ileal digestibility; Trp:Lys, tryptophan-to-lysine ratio; DDGS, distillers grains with solubles; STTD, standard total tract digestibility; COVID-19, coronavirus disease 2019 INTRODUCTION (Tokach et al., 2021). Therefore, pork producers were chal - lenged to find dietary strategies to decrease the growth rate In 2020, because of the COVID-19 global pandemic, pork of pigs. processing plants across the United States were either tem - Rao et al. (2021) and Helm et al. (2021) observed that porarily closed or had to decrease slaughter capacity due to pigs fed extremely low levels of Lys (all corn-based diets) the increased number of health-related employee absences. By had reduced ADG, gain-to-feed (G:F), and final body weight April 2020, one month after the United States government (BW). Soto et al. (2019) observed a 6.5% decrease in ADG issued a nationwide lockdown, processing plant capacity (i.e., as standardized ileal digestibility (SID) Lys decreased in the the level in which a processing plant uses its productive ca - diet from 0.75% to 0.45% in 100–125-kg pigs. In addition, pacity) decreased by 47% (USDA Agricultural Marketing altering the amino acid balance of the diet is another nutri - Service, 2020). As consequence, producers with pigs reaching tional strategy to investigate. Previous research has observed market weights were unable to access the processing plants that decreasing the ratio of Trp to Lys in the diet from 19% and had to find ways to reduce average daily gain (ADG) to 16% can reduce feed intake and decrease weight gain so pigs would not exceed packer upper weight limits which (Gonçalves et al., 2018). While there is considerable data would prevent harvesting. Swine producers have historically indicating the optimal nutrient fortifications to maximize aimed to improve growth rate and feed efficiency to decrease growth, there is limited data to examine nutrient alterations the time it takes for a pig to reach optimal marketing weight. to most efficiently slow growth rate and increase the amount The typical ADG during the finishing phase is between 800 of time needed to reach market weights in the event of a and 1,000 g/d with market weights of approximately 135 kg Received February 11, 2022 Accepted May 3, 2022. Published by Oxford University Press on behalf of the American Society of Animal Science 2022. This work is written by (a) US Government employee(s) and is in the public domain in the US. 2 Tolosa et al. processing plant or facility shutdowns. In response, this ex - MN). The barn was naturally ventilated and double-curtain- periment was conducted to determine the effect of reducing sided with a slatted concrete floor and deep manure storage. Lys and Trp on the growth performance of finishing pigs. Our Each pen (3.05 × 5.49 m) was equipped with a 5-hole stain - objective was to determine to what extent reducing the level less steel dry self-feeder (Thorp Equipment, Thorp, WI) and of SID Lys in diets for commercially raised grow-finish pigs a bowl waterer for ad libitum access to feed and water. The will decrease growth performance and to the extent that re - facility was equipped with a computerized feeding system ducing the tryptophan-to-lysine ratio (Trp:Lys) ratio would (FeedPro; Feedlogic Corp., Willmar, MN) that delivered and also decrease weight gain and slow down the growth of pigs recorded daily feed additions. The experiment was conducted in the finishing period. from June 19, 2020 to October 26, 2020. A total of 1,080 pigs (L337 × 1050, PIC; initially 32.0 kg) were used in a 119-d trial. Treatments were arranged in a MATERIALS AND METHODS randomized complete block design with 27 pigs per pen The Kansas State University Institutional Animal Care and and 10 pens per treatment. Initial pen weight served as Use Committee approved the protocol used in this study. the blocking factor. Dietary treatments were fed in seven phases and consisted of a control regimen (100% of the Animals and Diets estimated current SID Lys requirement curve for pigs in the The study was conducted at a commercial research-finishing New Horizon Farms production system) formulated to con - site in southwest Minnesota (New Horizon Farms, Pipestone, tain 1.10%, 1.01%, 0.91%, 0.83%, 0.79%, 0.71%, and Table 1. Composition of phases 1 and 2 experimental diets (as-fed basis) Phase 1 Phase 2 100 90 80 80%–16% Trp:Lys 100 90 80 80%–16% Trp:Lys Ingredient, % Corn 49.60 52.91 56.27 56.36 50.78 53.74 54.66 54.69 Soybean meal, 46.5% CP 7.51 4.25 0.93 0.87 3.86 0.79 – – DDGS 40.00 40.00 40.00 40.00 42.40 42.54 42.58 42.58 Limestone 1.39 1.42 1.44 1.44 1.42 1.44 1.45 1.45 Salt 0.46 0.46 0.46 0.46 0.45 0.45 0.45 0.45 l-Lys-HCl 0.68 0.65 0.63 0.63 0.67 0.65 0.55 0.55 dl-Met 0.05 0.02 – – 0.01 – – – l-Thr 0.12 0.10 0.09 0.08 0.11 0.10 0.05 0.05 l-Trp 0.07 0.07 0.07 0.04 0.08 0.07 0.06 0.04 Vitamin trace mineral premix 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Potassium chloride – – – – 0.10 0.10 0.10 0.10 Phytase 0.02 0.02 0.01 0.02 0.02 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 1.10 0.99 0.89 0.89 1.01 0.91 0.81 0.81 Ile:Lys 56 56 56 56 56 56 61 61 Met:Lys 31 30 30 30 30 30 33 33 Met and Cys:Lys 56 56 57 57 56 57 63 63 Thr:Lys 60 60 60 60 61 61 61 61 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 68 70 71 71 70 71 78 78 SID Lys:NE, g/Mcal 4.75 4.28 3.80 3.80 4.37 3.93 3.50 3.50 NE, kcal/kg 2,313 2,326 2,335 2,342 2,317 2,320 2,324 2,324 Ca, % 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 STTD P, % 0.36 0.35 0.32 0.34 0.36 0.33 0.33 0.33 Chemical analysis, % DM 86.98 87.12 87.58 87.25 87.36 87.68 87.40 86.99 CP 16.7 16.1 14.8 14.8 16.9 17.8 15.2 16.1 Experimental diets were fed for 2 and 4 weeks for phases 1 and 2, respectively. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 372–615 FTU per kg providing an estimated release ranging from 0.08 to 0.10 STTD P, %. DDGS, distillers grains with solubles; STTD, standard total tract digestibility. Dietary strategies to slow growth in pigs 3 0.67% SID Lys from 32 to 40, 40 to 51, 51 to 72, 72 to Statistical Analysis 85, 85 to 98, 98 to 112, and 112 to 130  kg, respectively. The pen was the experimental unit for all data. Response Two additional regimens contained 90% or 80% of the variables were analyzed using a general linear mixed model. SID Lys estimate. These three regimes were formulated to a Linear and quadratic contrasts were used to evaluate the ef - SID Trp:Lys ratio of 19% except for the last dietary phase fect of SID Lys reduction (treatments 100%, 90%, and 80%) which contained a 17% SID Trp:Lys ratio. The fourth reg- and a pairwise comparison was used to compare the 80% imen contained 80% of the SID Lys estimate with 16% SID SID Lys treatment with the 80%–16% SID Trp:Lys treat- Trp:Lys in all phases ( Tables 1–4). All diets were fed in meal ment. Heterogeneous residual variances as a function of the form and prepared at the New Horizon Farms feed mill response variables were fitted as needed. Model assumptions located in Pipestone, MN. were checked and considered to be appropriately met. The Pens of pigs were weighed, and feed disappearance was experimental data were analyzed using the lme4 package in measured approximately every 14 d throughout the exper - the R program (version 3.5.2, R Foundation for Statistical iment to determine ADG, average daily feed intake (ADFI), Computing, Vienna, Austria). Results were considered signifi - and G:F. In addition, pig removal, mortality, and evidence of cant at P ≤ 0.05 and a tendency at P ≤ 0.10. tail-biting were recorded. Two weeks before the end of the experiment, two pigs per pen were removed and marketed. RESULTS Later, final weights were obtained for the remaining pigs, and then they were marketed. No carcass data were collected be- For the overall period, ADG decreased (linear P, < 0.001), and a cause of restrictions to enter the processing plant due to the tendency (linear, P = 0.087) was observed for decreased G:F with ongoing outbreak of COVID-19. decreasing SID Lys (Table 5). The linear reduction in ADG was Table 2. Composition of phases 3 and 4 experimental diets (as-fed basis) Phase 3 Phase 4 100 90 80 80–16% Trp:Lys 100 90 80 80–16% Trp:Lys Ingredient, % Corn 53.65 54.75 54.95 54.98 61.42 62.41 62.63 62.65 Soybean meal, 46.5% CP 1.02 – – – 0.87 – – – DDGS 42.53 42.57 42.57 42.57 35.00 35.00 35.00 35.00 Limestone 1.31 1.32 1.32 1.32 1.26 1.27 1.27 1.27 Salt 0.45 0.45 0.45 0.45 0.49 0.49 0.45 0.45 l-Lys-HCl 0.65 0.57 0.45 0.45 0.58 0.51 0.40 0.40 l-Thr 0.11 0.07 0.01 0.01 0.10 0.07 0.01 0.01 l-Trp 0.07 0.06 0.05 0.02 0.07 0.06 0.04 0.02 Vitamin trace mineral premix 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Potassium chloride 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Phytase 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 0.91 0.82 0.73 0.73 0.83 0.74 0.66 0.66 Ile:Lys 56 60 68 68 56 60 67 67 Met:Lys 30 32 36 36 30 33 37 37 Met and Cys:Lys 56 61 69 69 58 63 70 70 Thr:Lys 62 62 62 62 63 63 63 63 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 71 76 86 86 72 77 87 87 SID Lys:NE, g/Mcal 3.95 3.56 3.16 3.16 3.51 3.16 2.81 2.81 NE, kcal/kg 2,315 2,320 2,320 2,320 2,366 2,357 2,359 2,359 Ca, % 0.53 0.53 0.53 0.53 0.51 0.51 0.51 0.51 STTD P, % 0.35 0.30 0.30 0.30 0.32 0.29 0.29 0.29 Chemical analysis, % DM 87.67 87.60 87.75 87.61 87.51 88.26 88.51 87.88 CP 17.9 16.3 16.0 16.1 18.15 15.9 16.4 16.2 Experimental diets were fed for 2 weeks. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 189–610 FTU per kg providing an estimated release ranging from 0.05 to 0.10 STTD P, %. 4 Tolosa et al. Table 3. Composition of phases 5 and 6 experimental diets (as-fed basis) Phase 5 Phase 6 100 90 80 80%–16% Trp:Lys 100 90 80 80%–16% Trp:Lys Ingredient, % Corn 65.90 67.52 67.69 67.71 67.51 67.66 67.80 67.82 Soybean meal, 46.5% CP 1.48 – – – – – – – DDGS 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 Limestone 1.20 1.21 1.21 1.21 1.16 1.16 1.16 1.16 Salt 0.52 0.45 0.45 0.45 0.45 0.45 0.45 0.45 l-Lys-HCl 0.53 0.49 0.39 0.38 0.49 0.40 0.31 0.31 l-Thr 0.10 0.07 0.02 0.02 0.08 0.04 – – l-Trp 0.06 0.05 0.04 0.02 0.06 0.04 0.03 0.01 Vitamin trace mineral premix 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Potassium chloride 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Phytase 0.02 0.01 0.01 0.02 0.01 0.01 0.01 0.01 Calculated analysis SID AA, % Lys 0.79 0.71 0.63 0.63 0.71 0.64 0.57 0.57 Ile:Lys 56 58 65 66 58 64 72 72 Met:Lys 30 32 36 37 32 35 40 40 Met and Cys:Lys 58 61 69 70 61 68 76 76 Thr:Lys 63 63 63 63 64 64 65 65 Trp:Lys 19.0 19.0 19.0 16.0 19.0 19.0 19.0 16.0 Val:Lys 72 75 85 85 75 83 94 94 SID Lys:NE, g/Mcal 3.31 2.98 2.65 2.65 2.98 2.69 2.39 2.39 NE, kcal/kg 2,381 2,381 2,381 2,392 2,381 2,381 2,381 2,381 Ca, % 0.49 0.49 0.49 0.49 0.47 0.47 0.47 0.47 STTD P, % 0.30 0.27 0.27 0.30 0.26 0.26 0.26 0.26 Chemical analysis, % DM 88.6 89.0 88.5 88.7 88.7 88.5 88.6 88.7 CP 15.7 15.5 15.1 15.4 13.4 13.1 13.4 14.3 Experimental diets were fed for 2 weeks. Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) was provided at a range of 244–610 FTU per kg providing an estimated release ranging from 0.06 to 0.10 STTD P, %. found in all three reported phases (d 0–42, 42–84, and 84–119) pandemic. The increasing number of worker-related absences whereas the feed efficiency response was only significant from d resulted in a decrease in the utilization capacity of pork proc - 0 to 42. Pigs fed 90% and 80% of the estimated Lys requirement essing plants. Consequently, there was a major reduction in for these pigs were approximately 4.3 and 8.6 kg lighter than the number of pigs that could be processed daily ( Millet et pigs fed at their estimated requirement. There was no evidence of al., 2021; Hayes et al., 2021). Producers were faced with pigs treatment differences (P = 0.176) observed in ADFI. reaching market weights without the opportunity of being Within the 80% SID Lys treatments, overall ADG and BW slaughtered resulting in pigs above the processing plants’ were decreased (P < 0.05) when a further reduction of the SID weight limits. Pigs exceeding this upper weight limit have Trp:Lys ratio was applied. Pigs fed the lower SID Trp:Lys ratio virtually no economic value to the producer. Thus, swine diet were 3.1 kg lighter than the 80% SID Lys treatment and producers were forced to find alternatives to slow down 11.7 kg lighter in final BW compared with those fed 100% of growth so pigs can stay in the facilities until processing plants the Lys requirement estimate. For feed efficiency, pigs tended either re-opened or had the processing capacity to accept pigs (P < 0.10) to have decreased G:F when the lower SID Trp:Lys within the weight limit (Tokach et al., 2021). ratio was applied. There were no differences (P > 0.05) in pigs Management strategies such as increasing barn tempera- removed, total mortality, and incidences of tail-biting were not ture or reducing the floor space allowance per pig in the pen observed throughout the study (data not shown). (crowding) can result in reduced growth but also negatively affect animal welfare ( Gonyou et al., 2006). Therefore, the most practical and favorable alternative to slow growth, while DISCUSSION not impacting animal welfare, is to use dietary strategies that The year 2020 was tremendously challenging for the swine reduce protein deposition, and therefore, decrease growth industry supply chain due to the impact of the COVID-19 rate of the pig. Dietary strategies to slow growth in pigs 5 Table 4. Composition of phase 7 experimental diet (as-fed basis) these reductions resulted in a linearly decreased ADG and G:F. Similarly,Li et al. (2012) evaluated the performance of grow- Phase 7 finish pigs at three different body weight ranges (i.e., 29–47, 54–76, and 84–109 kg) and observed that pigs fed less SID Lys Ingredient, % 100 90 80 80–16% Trp:Lys had reduced ADG and a decrease in G:F compared with pigs Ingredient, % fed greater concentrations of SID Lys. Their study fed pigs a diet with SID Lys reduced by 19.8%, 11.6%, and 19.1% of Corn 78.90 81.16 82.74 82.75 the requirement estimate in the previously mentioned weight Soybean meal, 3.62 1.54 – – 46.5% CP ranges (0.77 vs. 0.96, 0.68 vs. 0.77, and 0.55 vs. 0.68% SID Lys). These reductions resulted in an 8.8%, 6.4%, or 10.2% DDGS 15.00 15.00 15.00 15.00 decrease in ADG and a 12.8%, 9.1%, or 7.7% decrease in Limestone 1.09 1.10 1.11 1.11 feed efficiency. For the pigs in the heavier weight range (84– Salt 0.60 0.45 0.45 0.45 109  kg) the 19.1% SID Lys reduction resulted in a 2.9  kg l-Lys-HCl 0.40 0.39 0.35 0.35 lower final body weight after 28 d, therefore, these pigs would l-Thr 0.09 0.08 0.06 0.06 need 3.6 extra days to reach a maximum BW of 109  kg. A l-Trp 0.03 0.03 0.03 0.02 more recent study by Soto et al. (2019) using pigs over 100 kg Vitamin trace 0.09 0.09 0.09 0.09 (102  ±  0.4  kg) fed pigs up to 27.4% less SID Lys than the mineral estimated requirement for maximum ADG and observed that premix there was a linear reduction in ADG of pigs. This body of lit - Potassium 0.10 0.10 0.10 0.10 erature helped set the stage when producers had to reduce the chloride growth of their pigs due to extensive supply chain disruptions Phytase 0.02 0.02 0.02 0.02 within the industry during the COVID-19 pandemic. Also, Lipinate 0.05 0.05 0.05 0.05 an additional repeatable consequence of reducing the dietary Calculated analysis SID Lys level below requirement was a worsening of feed effi- ciency that must be considered. SID AA, % Other dietary alternatives to slow down growth include Lys 0.67 0.61 0.54 0.54 increasing the dietary fiber content of the diet that conse - Ile:Lys 56 56 58 58 quently reduces nutrient digestibility and increases digesta Met:Lys 29 31 33 33 viscosity and volume (frequently associated with satiety) Met and Cys:Lys 57 60 65 65 (Kerr and Shurson, 2013; Helm et al., 2021 ). However, Helm Thr:Lys 65 65 65 65 et al. (2021) fed pigs 75–105  kg BW a diet with increased Trp:Lys 17.0 17.0 17.0 16.0 levels of neutral detergent fiber (NDF) from 9.5% to 25% Val:Lys 71 73 77 77 and observed a tendency for a decrease in weight gain during the initial 7 d of feeding with no impact thereafter. SID Lys:NE, 2.77 2.49 2.22 2.22 g/Mcal Within the same experiment, Helm et al. (2021) aimed to severely impact growth by decreasing indispensable amino NE, kcal/kg 2,439 2,452 2,459 2,459 acid concentrations in the diet by either replacing 50% of Ca, % 0.45 0.45 0.45 0.45 soybean meal and feed-grade amino acids with corn or by STTD P, % 0.25 0.25 0.24 0.24 feeding a 97% corn-based diet without soybean meal or Chemical analysis, % feed-grade amino acids. These diets resulted in a decrease DM 87.4 87.5 87.8 87.5 of 0.37% and 0.76% of SID Lys, respectively; however, the CP 14.0 13.7 13.6 13.6 SID Trp:Lys increased from 0.18% to 0.22% and 0.26%, respectively. This reduction in SID Lys resulted in a linear de - Experimental diets were fed for 2 weeks. crease in ADG of 17% and 59% and G:F of 16% and 60% Provided per kg of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg when pigs were fed diets with 0.48% and 0.18% SID Lys vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, compared with pigs fed 0.77% SID Lys, respectively, which and 11 µg vitamin B12. 3 is in agreement with results from the current experiment. Optiphos 2000 (Huvepharma, Sofia, Bulgaria) provided at 615 FTU per kg with an estimated release of 0.10% available P. Rao et al. (2021) fed finishing pigs a diet with reduced SID Feed additive for animals used for managing carcass fat composition Lys where pigs in the control treatment were fed 0.70% SID (Nutriquest LLC, Mason City, IA). Lys and two additional diets were formulated at 0.50% and 0.18% SID Lys. They observed a 17.4% and 16.3% decrease Multiple amino acid titration studies aimed to estimate in ADG and a 14.9% and 15.2% reduction in G:F as SID Lys amino acid concentrations for optimal growth and efficiency was reduced in the diet from 0.70% to 0.50% and 0.18% of the pig have been conducted and help to understand that SID Lys, respectively. There was no impact on ADFI observed when essential or limiting amino acids, such as Lys and Trp, as SID Lys was reduced. were reduced, performance was impacted. Early studies by Furthermore, research has elucidated that an amino acid Hahn et al. (1995) illustrated that when Lys was fed below imbalance can result in detrimental effects on growth perfor - the requirement, daily gain and feed efficiency were affected mance. Reducing or increasing amino acids in the diet, can negatively. In their study,Hahn et al. (1995) determined that cause amino acid imbalances. Therefore, reducing the ratio the SID Lys requirement for barrows and gilts from 80 to of Leu, Val, or Trp in relation to Lys or increasing the sulfur 120  kg was 0.49 and 0.52%, respectively. The lowest level amino acids (SAA) to Lys ratio can consequently decrease the of SID Lys fed was 0.41%, which represented a reduction gain and overall growth of the pig ( Gonçalves et al., 2018 ; of 16.3% and 21.2% for barrows and gilts, respectively, and Cemin et al., 2019; Tokach et al., 2021). Edmonds and Smith 6 Tolosa et al. 1,2 Table 5. Effects of reducing SID Lys and SID Trp:Lys ratio on growth performance of grow-finish pigs 3 4 SID Lys, % P Item 100 90 80 80%–16% Trp:Lys SEM Linear Quadratic BW, kg d 0 32.3 32.4 32.4 32.3 0.87 0.507 0.630 a b d 42 66.4 65.0 62.4 60.0 1.13 0.001 0.185 c d d 84 102.2 99.2 96.0 93.5 1.28 0.001 0.947 a b d 119 134.0 129.7 125.4 122.3 1.40 0.001 0.999 d 0–42 a b ADG, kg 0.77 0.73 0.68 0.62 0.010 0.001 0.209 c d ADFI, kg 1.83 1.86 1.83 1.74 0.005 0.964 0.524 a b G:F 0.418 0.395 0.371 0.357 0.0591 0.001 0.869 d 42–84 ADG, kg 0.87 0.83 0.82 0.81 0.009 0.001 0.305 ADFI, kg 2.49 2.43 2.38 2.43 0.057 0.122 0.943 G:F 0.348 0.341 0.343 0.332 0.0943 0.752 0.66 d 84–119 ADG, kg 0.95 0.93 0.91 0.89 0.012 0.001 0.988 ADFI, kg 3.29 3.22 3.14 3.19 0.053 0.055 0.919 G:F 0.289 0.289 0.288 0.280 0.0692 0.887 0.969 Overall (d 0–119) a b ADG, kg 0.85 0.82 0.79 0.76 0.006 0.001 0.887 ADFI, kg 2.46 2.43 2.38 2.37 0.049 0.176 0.786 d c G:F 0.349 0.339 0.333 0.323 0.0550 0.087 0.862 A total of 1,080 pigs (initially 32.3 kg) were used with 27 pigs per pen and 10 replications per treatment. BW = body weight; ADG = average daily gain; ADFI = average daily feed intake; G:F = gain-to-feed ratio. Standardized ileal digestible (SID) Lys of the estimated requirement (100%, 90%, or 80%) or 80% with an additional reduction of SID Trp:Lys ratio to 16%. Treatments 100, 90 and 80 were fed 19% Trp:Lys ratio from 0 to 98d with the exception of the last phase were the ratio of Trp:Lys was 17%, from 98 to 119d. Linear and quadratic contrasts included treatments 100, 90 and 80. a,b Treatment: 80 vs. 80–16% Trp:Lys differ (P ≤ 0.05). c,d Treatment: 80 vs. 80–16% Trp:Lys differ (P ≤ 0.10). (2021) evaluated increasing the level of SAA by increasing the ADG and ADFI was observed for growing and finishing pigs level of feed-grade Met in the diet. Their diets resulted in an from 50 to 80 and 80 to 110 kg resulting in final BW being increased ratio of SID SAA:Lys from 3.87% to 5.05% on pigs reduced by 1.9 or 2.2 kg, respectively, which was explained from 109 to 144 kg. Increasing SID SAA:Lys ratio in the diet by a reduction in ADG and ADFI when fed 15% vs. 18% resulted in a significant reduction in ADG of 62% when pigs SID Trp:Lys ratio for both bodyweight ranges. Reducing SID were the fed highest level of SAA compared to pigs fed the Trp:Lys in a diet that is also deficient in Lys was observed to lowest SAA:Lys ratio. In addition, Trp is typically the second further decrease growth and resulted in a lighter pig compared limiting amino acid in corn-soybean meal-based diets and acts with pigs fed a diet with Lys at the requirement in the current as a precursor to important biological roles, such as the syn - experiment, which is in agreement with previous data (Salyer thesis of serotonin, which is associated with regulating stress, et al., 2013; Gonçalves et al., 2018 ; Liu et al., 2019). All in sleep, and appetite ( Le Floc’h and Seve, 2007 ). Therefore, re- all, this information illustrates the impact that amino acid ducing the level of Trp in relation to Lys in the diet can further imbalances in the diet have on the performance of grow-finish reduce growth by decreasing feed intake. Multiple studies pigs. Previous trials were carried out with small groups of have evaluated the response in performance of pigs fed a diet pigs and in university research facilities, therefore, data were formulated with varying ratios of Trp:Lys.Salyer et al. (2013) needed to evaluate the effect of reducing Lys and Trp to Lys noted that ADG, ADFI, and BW were negatively impacted if ratio on growth performance utilizing larger pig groups and pigs were fed less than 16.5 and 19.5% SID Trp:Lys from 36 commercial facilities. To the best of our knowledge, this is the to 73 and 66 to 124 kg of BW, respectively. This is consistent first study that has been carried out under field conditions with Gonçalves et al. (2018) that observed reducing Trp in the that evaluated the effect of reducing Lys and Trp:Lys ratio in diet from 19% to 16% of Lys resulted in reduced feed intake diets on the growth performance of finishing pigs and decreased weight gain, and therefore, reduced G:F. In a The current study showed that if producers fed 80% of the similar fashion, Liu et al. (2019) conducted two experiments SID Lys requirement to pigs starting at 32 kg, it would take evaluating various SID Trp:Lys ratios in a diet fed to pigs 10.9 more days to reach 134 kg which was the final weight from 50 to 80 and 80 to 110 kg, and it was estimated that of the pigs fed the diet formulated to meet the amino acid the optimal SID Trp:Lys ratio for maximum ADG was 18% requirements. In addition, if pigs were fed a diet with 80% for both bodyweight ranges. A quadratic reduction in both SID Lys and 16% SID Trp:Lys, it would take an additional Dietary strategies to slow growth in pigs 7 Hahn, J. D., R. R. Biehl, and D. H. Baker.1995. Ideal digestible lysine 4.5 days (a total of 15.4 days) to achieve the same weight. level for early- and late-finishing swine.J . Anim. Sci. 73:773–784. This dietary strategy would enable producers to provide doi:10.2527/1995.733773x. pigs more time in the barn avoiding becoming too heavy Hayes, D. J., L. L. Schulz, C. E. Hart, and K. L. Jacobs.2021. A descrip- and risking economic penalties or acceptance to processing tive analysis of the COVID-19 impacts on U.S. pork, turkey, and plants. egg markets. Agribusiness 37:122–141. doi: 10.1002/agr.21674. In conclusion, the COVID-19 pandemic forced pork Helm, E. T., J. F. Patience, M. R. Romoser, C. D. Johnson, J. W. Ross, and N. producers and nutritionists to evaluate situations that had K. Gabler. 2021. Evaluation of increased fiber, decreased amino acids, not been a priority of the industry in the past and that can be or decreased electrolyte balance as dietary approaches to slow finish - helpful in future scenarios, such as human disease pandemics ing pig growth rates. J. Anim. Sci. 7:1–9. doi:10.1093/jas/skab164. or supply chain disruptions This study presents useful in - Kerr, B. J., and G. C. Shurson. 2013. Strategies to improve fiber utili - zation in swine. J. Anim. Sci. Biotechnol. 4:11. doi:10.1186/2049- formation to producers regarding dietary changes to slow the 1891-4-11. growth of pigs during the grow-finish period. Le Floc’h, N., and B. Seve. 2007. Biological roles of tryptophan and its metabolism: Potential implications for pig feeding. Livest. Sci. 112(1–2):23–32. ACKNOWLEDGMENTS Li, P., Z. Z, W. D, X. L, R. Zhang, and P. X. 2012. Effects of the Contribution no. 22-231-J of the Kansas Agricultural standardized ileal digestible lysine to metabolizable energy ratio on Experiment Station, Manhattan, 66506-0201. We would like performance and carcass characteristics of growing-finishing pigs. to thank the staff of New Horizon Farms, Pipestone MN, for J. Anim. Sci. Biotechnol. 3:9. doi:10.1186/2049-1891-3-9. Liu, J. B., H. L. Yan, S. C. Cao, J. Liu, X. Z. Li, and H. F. Zhang. use of animals and technical support. 2019. The response of performance in grower and finisher pigs to diets formulated to different tryptophan to lysine ratios. Li v. Sci. 222:25–30. doi:10.1016/j.livsci.2019.01.016. Conflict of interest statement Millet, S., S. De Smet, E. F. Knol, B. G, P. Trevisi, S. Vigors, K. Nilsson, None declared. and J. Van Meensel. 2021. How two concurrent pandemics put a spoke in the wheel of intensive pig production. Anim. Frontiers 11:14–18. doi:10.1093/af/vfaa051. LITERATURE CITED Rao, Z., M. D. Tokach, J. C. Woodworth, J. M. DeRouchey, R. D. Goodband, Cemin, H. S., M. D. Tokach, S. S. Dritz, J. C. Woodworth, J. M. and J. T. Gebhardt. 2021. Evaluation of nutritional strategies to slow DeRouchey, and R. D. Goodband.2019. Meta-regression analysis growth rate then induce compensatory growth in 90-kg finishing pigs. to predict the influence of branched-chain and large neutral amino Transl. Anim. Sci 5:1–11. doi:10.1093/tas/txab037. acids on growth performance of pigs. J. Anim. Sci. 97:2505–2514. Salyer, J. A., M. D. Tokach, J. M. DeRouchey, S. S. Dritz, R. D. doi:10.1093/jas/skz118. Goodband, and J. L. Nelssen.2013. Effects of standardized ileal Edmonds, M. S., and J. W. Smith. 2021. Amino acid imbalance with digestible tryptophan:lysine in diets containing 30% dried distillers excess methionine in late-finishing pigs: effects on performance grains with solubles on finishing pig performance and carcass traits. and carcass quality. Trans. Anim. Sci 5:197. doi:10.1093/tas/ J. Anim. Sci. 91:3244–3252. doi:10.2527/jas.2012-5502. txab197. Soto, J. A., M. D. Tokach, S. S. Dritz, J. C. Woodworth, J. M. DeRouchey, Gonçalves, M. A. D., M. D. Tokach, N. M. Bello, K. J. Touchette, R. R. D. Goodband, and F. Wu. 2019. Optimal dietary standardized D. Goodband, J. M. DeRouchey, J. C. Woodworth, and S. S. Dritz. ileal digestible lysine and crude protein concentration for growth 2018. Dose–response evaluation of the standardized ileal digest - and carcass performance in finishing pigs weighing greater than ible tryptophan: lysine ratio to maximize growth performance 100 kg. J. Anim. Sci. 97:1701–1711. doi:10.1093/jas/skz052. of growing-finishing gilts under commercial conditions. Animal Tokach, M. D., B. D. Goodband, J. M. DeRouchey, J. C. Woodworth, 12:1380–1387. doi:10.1017/S1751731117002968. and J. T. Gebhardt. 2021. Slowing pig growth during COVID-19, Gonyou, H. W., M. C. Brumm, E. Bush, J. Deen, S. A. Edwards, T. models for use in future market fluctuations. Anim. Front. 11:23– Fangman, J. J. McGlone, M. Meunier-Salaun, R. B. Morrison, 27. doi:10.1093/af/vfaa047. H. Spoolder, et al. 2006. Application of broken-line analysis to USDA Agricultural Marketing Service 2020. National daily direct assess floor space requirements of nursery and grower-finisher hog prior day—slaughtered swine [accessed November 22, 2020]. pigs expressed on an allometric basis.J . Anim. Sci. 84:229–235. https://mpr.datamart.ams.usda.gov/menu.do?path=Products\Hogs\ doi:10.2527/2006.841229x. Daily%20Swine

Journal

Translational Animal ScienceOxford University Press

Published: May 6, 2022

Keywords: grow-finish pigs; lysine; slow down growth; tryptophan

References