Branched-chain amino acids (BCAA) are a collective group of amino acids (AA) made up of Leucine (Leu), Valine (Val), and Isoleucine (Ile). These three AA all share the first steps of catabolism, and an excess of one can lead to increased catabolism of all BCAA. Other AA such as Tryptophan (Trp) also interact with BCAA in normal metabolism. Finishing pig diets containing DDGS are often formulated with high inclusions of Lys-HCl and low soybean meal which leads to higher than optimum levels of Leu in relation to Val, Ile, and Trp. A recent meta-analysis (Cemin, 2019) suggested that high Leu diets require higher than normal ratios of Val, Ile, and Trp in order to maintain growth performance. However, data was not available to confirm this hypothesis and consequently two trials were conducted to determine if increasing the level of added Val, Ile, and Trp in low SBM/high Lys-HCl diets that have high Leu would improve performance of grow finish pigs. In the first trial a control diet with DDGS, higher SBM and low Lys-HCl was compared to DDGS-containing diets with lower SBM and higher Lys-HCl that were supplemented with higher levels of Val, Ile, and/or Trp. This study confirmed the negative impact on growth performance from diets with high levels of Leu when low levels of Val, Ile, and Trp were also present. However, supplementing increased levels of Val and Ile improved performance. The meta-analysis model was relatively accurate in predicting the performance of the pigs in this study. In the second trial a control diet with higher SBM and low Lys-HCl was compared to three diets with low SBM and high Lys-HCl with low, medium, or high ratios of Val, Ile, and Trp in relation to Leu. In this trial, the low ratio was close to published requirements of pigs, the medium ratio was slightly higher than those typically used to maximize growth performance, and the high ratio was much higher than typical commercial diets. Results showed that increasing the ratios of Val, Ile, and Trp from low to medium improved performance, but no additional benefit was observed from going to high supplementation levels. The prediction model was relatively accurate in predicting the performance of the medium ratio treatment but overestimated the performance of the high ratio treatment. This data suggests that increased supplementation of Val, Ile, and Trp are needed to improve growth performance when low SBM/high Lys-HCl diets that contain elevated Leu are fed, but high supplementation levels do not provide additional benefit. Collectively these trials show that when DDGS diets are fed that contain low SBM and high inclusions of Lys-HCl, the combination of high Leu and low Val, Ile, and Trp will result in poorer performance. Increasing the Val, Ile, and Trp to levels higher than typically formulated will restore performance. These trials provide solutions to producers to take advantage of lower diet costs when feeding DDGS diets with low SBM and high Lys-HCl in order to maintain growth performance similar to a higher priced diet containing higher levels of SBM. For more information, contact Dr. Jason Woodworth (JWoodworth@ksu.edu).
• Diets containing DDGS and high Lys-HCl with low SBM will result in pig growth performance lower than that observed with higher SBM diets, most likely as a result of an imbalance of branch chain amino acids.
• A recent meta-analysis resulted in a prediction equation that estimates growth performance based on the dietary concentrations of Leu, Val, Ile, and Trp.
• These trials helped validate the prediction equation and show that when increased concentrations of Leu are present in the diet, higher than normal levels of Val, Ile, and Trp are needed to optimize finishing pig growth performance.
• This data illustrates an opportunity for producers to take advantage of lower diet costs when feeding DDGS diets with low SBM and high Lys-HCl in order to maintain growth performance similar to a higher priced diet containing higher levels of SBM.