A meta-regression analysis to evaluate the influence of branched-chain amino acids in lactation diets on sow and litter growth performance

The branched-chain amino acids (BCAA) Ile, Leu, and Val are three dietary essential amino acids for lactating sows; however, effects of dietary BCAA on sow and litter growth performance in the literature are equivocal. Thus, a meta-regression analysis was conducted to evaluate the effects of BCAA and their interactions in lactating sow diets to predict litter growth performance, sow bodyweight change, and sow feed intake. Thirty-four publications that represented 43 trials from 1997 to 2020 were used to develop a database that contained 167 observations. Diets for each trial were reformulated using NRC. 2012. Nutrient requirements of swine. 11th ed. Washington, DC: National Academies Press nutrient loading values in an Excel-based spreadsheet. Amino acids were expressed on a standardized ileal digestible (SID) basis. Regression model equations were developed with the MIXED procedure of SAS (Version 9.4, SAS Institute, Cary, NC) and utilized the inverse of reported squared SEM with the WEIGHT statement to account for heterogeneous errors across studies. Predictor variables were assessed with a step-wise manual forward selection for model inclusion. Additionally, statistically significant (P < 0.05) predictor variables were required to provide an improvement of at least 2 Bayesian information criterion units to be included in the final model. Significant predictor variables within three optimum equations developed for litter ADG included the count of weaned pigs per litter, NE, SID Lys, CP, sow ADFI, Val:Lys, Ile:Lys, and Leu:Val. For sow BW change, significant predictor variables within two developed models included litter size at 24 h, sow ADFI, Leu:Lys, and Ile + Val:Leu. The optimum equation for sow ADFI included Leu:Trp, SID Lys, NE, CP, and Leu:Lys as significant predictor variables. Overall, the prediction equations suggest that BCAA play an important role in litter growth, sow BW change, and feed intake during lactation; however, the influence of BCAA on these criteria is much smaller than that of other dietary components such as NE, SID Lys, sow ADFI, and CP. Prediction equations developed for lactating sow and litter growth performance suggest that branched-chain amino acids play an important role in litter growth, sow bodyweight change, and feed intake during lactation. Lay Summary The branched-chain amino acids Ile, Leu, and Val are three dietary essential amino acids necessary for both skeletal and milk protein synthesis of lactating sows. Since the late 1990s, sows are producing much larger and heavier litters and commonly receive diets with greater concentrations of crystalline amino acids. This practice unintentionally increases Leu and may create imbalances among the dietary branched-chain amino acids. Nonetheless, sow and litter growth responses to branched-chain amino acids and large neutral amino acids such as Trp are equivocal within the available literature. Therefore, a meta-regression analysis was conducted to evaluate the effects of branched-chain amino acids and their interactions in lactating sow diets to predict litter growth performance, sow bodyweight change, and sow feed intake. The developed models for litter average daily gain suggest that Leu, Ile, and Val impact litter growth, but the effects of branched-chain amino acids are much smaller than the effects of dietary net energy, Lys, and crude protein. Furthermore, the developed models suggest that increasing Leu:Lys and reducing Ile + Val:Leu ratios can positively influence sow bodyweight change during lactation. Additionally, our model suggests that reduced Leu:Trp and increased Leu:Lys positively influence sow feed intake during lactation.