Effects of different dietary methionine and cysteine ratios on growth performance and intestinal development of broilers from brain-gut peptide secretion perspective.

Abstract

The objective of this study is to investigate the nutritional metabolism and growth development of broiler chickens under different methionine (Met)-to-cysteine (Cys) ratios, with a focus on proteomic alterations in the hypothalamus and ileum to elucidate potential regulatory mechanisms. A total of 216 one-day-old Arbor Acres broiler chicks were randomized into three groups: low (LMCR, 0.34%:0.56%), medium (MMCR, 0.45%:0.45%), and high (HMCR, 0.53%:0.37%) Met-to-Cys ratios, with total sulfur amino acids fixed at 0.9%. Each group comprised 6 replicates of 12 chicks, and the experiment spanned 21 days. On day 22, the birds were fasted for 12 hours before slaughter to collect serum, hypothalamus and ileum samples for comprehensive analysis of metabolic hormones, neurotransmitters and proteomic profiles. Results demonstrated that HMCR improved average daily gain (p<0.05), reduced feed conversion ratio (p<0.05), and enhanced protein/lipid utilization efficiency. Mechanistically, HMCR promoted hypothalamic neurodevelopment, downregulated key components of the protein kinase A signaling pathway (p<0.05) and leptin expression (p<0.001), while upregulating growth hormone and gastrointestinal hormone secretion. Through the hypothalamic-hormonal-ileal axis, HMCR modulated ileal cell physiology by upregulating inositol 1,4,5-trisphosphate receptors (p<0.05) and phosphoinositide 3-kinase (p<0.05), thereby enhancing ileal villus morphology and nutrient absorption capacity. The improved ileal structure further augmented energy utilization efficiency (p<0.05). In conclusion, a dietary Met:Cys of 0.53%:0.37% optimizes broiler growth performance by coordinately regulating metabolic pathways in the hypothalamus and ileum, as well as modulating brain-gut peptide signaling. These findings provide a scientific foundation for formulating sulfur amino acid-optimized diets to enhance poultry productivity and feed efficiency.