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Effects of the different ratios of branched chain amino acids (BCAAs) on growth performance, meat quality, and intestinal health in broilers fed with low and high crude protein diet

Goo, D., A. Singh, J. Choi, M. Sharma, D. Paneru, J. Lee and W. Kim

The branched-chain amino acids (BCAA), including leucine (Leu), valine (Val), and isoleucine (Ile), are indispensable amino acids with similar structures, and impact poultry growth, intestinal health, and immunity. In general, poultry feed contains more Leu than Val and Ile. However, when chickens are fed low crude protein (CP) diets, there can be an imbalance in BCAAs, negatively affecting growth performance. Therefore, we aimed to investigate how different BCAA ratios in both low and high CP diets influence growth performance, meat quality, and intestinal health in broilers. The study was conducted using a completely randomized design, employing a 4 × 2 factorial arrangement. A total of 1,280 0-d-old male Cobb 500 broilers were allotted to 8 groups, each with 8 replicates, and raised until 42 days. The four different BCAA ratios were as follows: 1) Low Leu + high Val/Ile; 2) Normal BCAAs with soybean meal (SBM) without wheat middling (WM); 3) Normal BCAAs with WM; and 4) High Leu + Low Val/Ile. The two different dietary CP groups were: 1) Low CP (Starter, 20.5%; Grower, 18.5%; and Finisher, 17.5%); 2) High CP (Starter, 22.5%; Grower, 20.5%; and Finisher, 19.5%). All data were subjected to statistical analysis using 2-way ANOVA, and Tukey’s HSD test or Student’s t-test was applied if the P < 0.05. The Low CP group significantly in- creased body weight gain (BWG), feed intake (FI), carcass weight, and relative pectoralis major weight when compared to the High CP group (P < 0.001). The High Leu + Low Val/Ile group significantly decreased BWG, FI, feed efficiency, carcass weight, and relative pectoralis major/ minor weight when compared to the other BCAA ratio groups (P < 0.001). The Normal BCAAs with SBM group significantly increased BWG and feed efficiency when compared to the Normal BCAAs with WM group (P < 0.001). No significant differences were observed in intestinal mor- phology and microbiota analysis among all the treatments.

In conclusion, maintaining a well-balanced BCAAs ratio based on SBM without WM has a positive effect on chicken growth, and a marginally-low CP diet can also help improve growth performance with the current BCAA ratio. Further studies are necessary to determine optimal BCAA balance when the chickens are fed high SBM/protein diets.