Understanding the interactive effects of dietary leucine with isoleucine and valine in the modern commercial broiler

A study was conducted to understand the relationship among dietary branched-chain amino acids (BCAA) on the performance of Ross 344 pound 708 male broilers. A total of 2,592 d-old male chicks were randomly placed into 144 -floor pens according to a 23 full factorial central composite design (CCD) with 20 treatments (14 treatments and 6 center points). Each treatment consisted of varying digestible Ile:Lys (52 to 75), Val:Lys (64 to 87), and Leu:Lys (110 to 185) ratios. Birds and feed were weighed at 20 and 34 d of age to determine body weight gain (BWG), feed intake, and feed conversion ratio (FCR). At 35 d of age, feather amino acid composition and carcass characteristics were evaluated. Data were analyzed as CCD using the surface response option of JMP v. 15. Body weight gain (1,332 g; P < 0.001; R2 = 0.93) and FCR (1.54; P = 0.002; R2 = 0.88) were optimized at the lowest Leu:Lys ratio (110) with moderate Val:Lys (78 to 79) and Ile:Lys (65 to 66) ratios. Poorer BWG and FCR were observed as Leu:Lys ratio increased while increasing Val:Lys and Ile:Lys ratios alleviated the poor performance. Carcass (71.5%; P = 0.031; R2 = 0.76) and breast yield (26.7%; P < 0.001; R2 = 0.96) were maximized at the highest Leu:Lys ratio. This effect was complemented by increasing Ile:Lys ratio beyond 68. Lower Ile:Lys and Val:Lys ratios were required to maximize carcass and breast yield at the lowest Leu:Lys ratio. However, this strategy yielded less meat than providing a high Leu:Lys ratio diet. Dietary BCAA had little effect on altering the composition of feather protein and amino acid (P > 0.10). These results suggest that optimum BCAA ratios to Lys may vary depending on response criteria and demonstrate the importance of maintain-ing proper Val and Ile ratios centered on dietary Leu. Live performance can be optimized in diets with low Leu:Lys ratios; however, meat yield can be enhanced by increasing dietary Leu:Lys along with Ile:Lys ratios.

Automated summary

This study aimed to understand the impact of dietary branched-chain amino acid ratios on the performance of male broilers. The results showed that diets with lower Leu:Lys ratios optimized live performance, while increasing Leu:Lys and Ile:Lys ratios enhanced meat yield.