ABSTRACT
Dietary fat affects appetite and appetite-related peptides in birds and mammals; however, the effect of dietary fat on appetite is still unclear in chickens faced with different energy statuses. Two experiments were conducted to investigate the effects of dietary fat on food intake and hypothalamic neuropeptides in chickens subjected to two feeding states or two diets. In Experiment 1, chickens were fed a high-fat (HF) or low-fat (LF) diet for 35â days, and then subjected to fed (HF-fed, LF-fed) or fasted (HF-fasted, LF-fasted) conditions for 24â h. In Experiment 2, chickens that were fed a HF or LF diet for 35â days were fasted for 24â h and then re-fed with HF (HF-RHF, LF-RHF) or LF (HF-RLF, LF-RLF) diet for 3â h. The results showed that chickens fed a HF diet for 35â days had increased body fat deposition despite decreasing food intake even when the diet was altered during the re-feeding period (P<0.05). LF diet (35â days) promoted agouti-related peptide (AgRP) expression compared with HF diet (P<0.05) under both fed and fasted conditions. LF-RHF chickens had lower neuropeptide Y (NPY) expression compared with LF-RLF chickens; conversely, HF-RHF chickens had higher NPY expression than HF-RLF chickens (P<0.05). These results demonstrate: (1) that HF diet decreases food intake even when the subsequent diet is altered; (2) the orexigenic effect of hypothalamic AgRP; and (3) that dietary fat alters the response of hypothalamic NPY to subsequent energy intake. These findings provide a novel view of the metabolic perturbations associated with long-term dietary fat over-ingestion in chickens.