Different dietary branched-chain amino acid ratios, crude protein levels, and protein sources can affect the growth performance and meat yield in broilers

Authors: GOO, DOYUN - University Of Georgia; SINGH, AMIT - University Of Georgia; CHOI, JANGHAN - Oak Ridge Institute For Science And Education (ORISE); SHARMA, MILAN - University Of Georgia; PANERU, DEEPENDRA - University Of Georgia; LEE, JIHWAN - University Of Georgia; KATHA, HEMANTH - University Of Georgia; Zhuang, Hong; Kong, Byungwhi; Bowker, Brian; KIM, WOO KYUN - University Of Georgia

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2024
Publication Date: 9/7/2024
Citation: Goo, D., Singh, A.K., Choi, J., Sharma, M.K., Paneru, D., Lee, J., Katha, H.R., Zhuang, H., Kong, B.C., Bowker, B.C., Kim, W. 2024. Different dietary branched-chain amino acid ratios, crude protein levels, and protein sources can affect the growth performance and meat yield in broilers. Poultry Science. 103(12):104313.
DOI: https://doi.org/10.1016/j.psj.2024.104313

Interpretive Summary: Crude proteins (CP) play an important role in modern broiler diet. However, high CP diet also results in increased nitrogen and ammonia emissions. Therefore, reducing CP in broiler diets has been gaining attention in recent years. The objective of the current study was to investigate the effect of adding different contents (low, medium, and high) of dietary branched-chain amino acid (BCAA) leucine or using different protein sources (soybean meal vs. wheat middling) with changed CP levels (low CP diet, 1% lower than the Cobb 500 Broiler Performance and Nutrition Supplement vs. high CP diet 1% higher than the Cobb 500 Broiler Performance and Nutrition Supplement) on the growth performance, carcass weight, body and mineral composition, meat quality, breast muscle gene expression, and amino acid digestibility of broiler chickens and litter quality. Our data showed that the high leucine diet had a negative effect on overall chicken growth performance, carcass weight, chicken breast muscle weight, and body mineral composition compared to the low and medium leucine groups, particularly in the high CP diet. The soybean meal group showed increased chicken growth performance, chicken breast muscle weight, and expression of genes promoting muscle growth and improved bone mineral composition compared to the wheat middling group, and the high CP group intensified the negative effect of the wheat middling diet. The results suggest that there are interaction effects between BCAA content and CP level and between protein source and CP level on chicken performance and carcass/bone mineral composition. Excessive BCAA leucine in the diets may negatively affect growth performance and meat yield in chickens.

Technical Abstract: Balanced ratios of branched-chain amino acids (BCAAs) can enhance chicken growth, immunity, and muscle synthesis. However, these ratios can be affected by changes in crude protein (CP) levels or the substitution of protein sources, leading to BCAA antagonism. This, in turn, can have a negative impact on chicken growth. In Experiment 1, a total of 960 0-d-old male Cobb 500 broilers were divided into 6 treatments with 8 replicates. Three different BCAA ratios were used in High or Low CP diets as follows: 1) Low Leu group (Low level of leucine with increased valine and isoleucine levels), 2) Med Leu group, and 3) High Leu group (High level of leucine with reduced valine and isoleucine levels) for a total of 6 diets. In Experiment 2, a total of 640 0-d-old male Cobb 500 broilers were divided into 4 treatments with 8 replicates. The four diets had either High or Low CP and one of two protein sources with the same medium levels of BCAAs: 1) the soybean meal (SBM) group, which had SBM as the main protein source, and 2) the wheat middlings with non-bound AAs (WM+AA) group, which had additional non-bound AAs to replace SBM. The High Leu diet had a negative effect on overall growth performance, carcass weight, breast muscle weight, and body mineral composition compared to the Low Leu and Med Leu groups, particularly in the High CP diet (P < 0.05). The SBM group showed increased growth performance, breast muscle weight, expression levels of genes promoting muscle growth, and improved bone mineral composition compared to the WM+AA group, and the High CP group intensified the negative effect of the WM+AA diet (P < 0.05). In summary, balanced BCAA ratios and SBM-based diets have positive effects on chicken growth and muscle accretion, whereas excessive leucine and non-bound AA levels in the diets may negatively affect growth performance and meat yield in chickens.