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Effects of varying branched-chain amino acid ratio using corn gluten meal, L-isoleucine, and L-valine on 0-21d turkey poult performance

Estanich, E., K. Bowen, L.Knarr, E. Lynch, S. Noll, A. Garcia Morales and J. Moritz

Providing amino acids (AA) in concentrations that optimize production performance is critical to turkey production. The branched-chain amino acids (BCAA) leucine (Leu), isoleucine (Ile), and valine (Val) are essential AA needed for protein synthesis and energy production, in addition to performing anabolic signaling functions via activation of the mechanistic target of rapamycin (mTOR) pathway. Due to the similarity of chemical structure among the three BCAA, imbalanced dietary ratios can lead to metabolic competition and enzymatic degradation of limiting BCAA, particularly in diets with excess Leu. Concentrated corn protein ingredients such as corn gluten meal (CG) contain high levels of Leu and thus can alter BCAA requirement; however, L-Ile and L-Val may be added to balance BCAA ratios. The objective of this study was to evaluate the effects of manipulating BCAA ratios in diets using CG, L-Ile, and L-Val on live performance of Nicholas Select turkey hens from 0-21d of age. Using a 38.4% corn and 49.8% soybean meal-based diet as the Control, five treatments were created to model the impact of BCAA ratio: Low CG (5.5%), High CG (11%), High CG + Val, High CG + Ile, and High CG + Val + Ile. Formulated Leu:Lys ratios were 1.30, 1.43, 1.60, 1.58, 1.60, and 1.58, respectively. Diets were fed to 15 replicate cages of 8 poults from 0-3d and 6 poults from 3-21d, utilizing a randomized complete block design. Performance was measured on day 14 and 21 and analyzed using a one- way ANOVA followed by Fisher’s LSD test where appropriate (α=0.05). Performance data at day 14 and 21 indicated that High CG decreased feed intake, bird weight, live weight gain, and increased feed conversion ratio relative to the Control (P<0.05). Additions of L-Ile and L-Val produced performance equivalent to the Control (P<0.05) at d14 and decreased feed conversion ratio relative to the Control (P<0.05) at d21.

These results suggest that starter diets containing high Leu from a concentrated corn protein ingredient can decrease hen performance but may be restored with additions of L-Iso and L-Val. However, in practical settings, nutritionists should assess the costs associated with BCAA supplementation versus diets with high inclusions of soybean meal.