The Effect of Branched-Chain Amino Acids (L-Valine, L-Leucine and L-Isoleucine) on Intestinal Morphology and IGF-1 Gene Expression in Broiler Chickens

Background: Insulin-like growth factor 1 (IGF-1) is an important regulator of growth, amino acid (AA) elongation, glucose metabolism, DNA synthesis, protein synthesis, and the proliferation and differentiation of various cell types. Therefore, IGF-1 may affect intestinal morphology by increasing nutrient uptake into intestinal enterocytes and promoting cell proliferation. Objectives: The present study aimed to evaluate the effects of different levels of branched-chain amino acids (BCAAs) (L-valine, L-leucine, and L-isoleucine) in low crude protein (CP) diets on intestinal morphology and IGF-1 gene expression in broiler chickens. Methods: A total of 480 one-day-old male and female broilers of the Ross 308 strain, with an average weight of 42.75 ± 0.47 g, were used. This experiment was carried out as a 3 × 2 factorial in the form of a completely randomized design with 6 treatments and 4 replications. The experimental diets included three levels of BCAA (0%, 10%, and 20% higher than the standard) and two levels of CP (standard or 10% lower than the standard). Results: Using 20% BCAA in the diet increased the villus height to crypt depth (VH/CD) ratio in the duodenum, jejunum, and ileum compared to the standard level of BCAA (P < 0.05). Reducing CP by 10% significantly lowered the VH/CD ratio in the duodenum, jejunum, and ileum (P < 0.05). The expression of IGF-1 mRNA in liver tissue was higher in the groups containing 10% BCAA than in the standard BCAA groups, regardless of the CP level. Conclusions: In general, BCAA supplementation could be beneficial for improving intestinal morphology and IGF-1 gene expression in broiler chickens on low CP diets.