Glucose Intake during the Neonatal Period Modulates the Central Melanocortin System with Breed-Specific Differences

Glucose is the primary substrate for cellular energy production, and its blood concentration is tightly regulated. This study investigated the effect of glucose supplementation during the first three days post-hatching on growth performance and diencephalic melanocortin-related gene expression in Red Cornish (RC) and Yamanashi Oh-Shamo (OSH-Y) chicks. We observed that body weight and weight gain were significantly higher in RC than in OSH-Y chicks. Glucose administration reduced body weight and feed intake at three days of age although no differences persisted thereafter. Significant differences in the expression of agouti-related peptide, AMP-activated protein kinase α2, cholecystokinin A receptor, and insulin receptor genes were detected between the two breeds. Conversely, neuropeptide Y was significantly downregulated by glucose supplementation in both breeds. Melanocortin receptor subtypes 3, 4, and melanocortin receptor accessory protein 2 exhibited significant breed and treatment interactions, with higher expression detected in glucose-fed OSH-Y chicks. These findings indicate that newly hatched chicks possess a centrally mediated glucose-sensing system that transiently suppresses feed intake. The more pronounced response observed in OSH-Y chicks suggests heightened hypothalamic glucose sensitivity, possibly mediated by the activation of melanocortin receptor signaling.