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

OBJECTIVE: 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. METHODS: 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: Results demonstrated that HMCR improved average daily gain (p