Feed color modifies hypothalamic appetite gene regulation and gut function in broiler chickens

This study aimed to study the impact of feed color on hypothalamic appetite gene regulation, gut function, and performance of broiler chickens. A total of 280 male broiler chicks (Ross 308) were randomly assigned to 20 pens (14 chicks/pen; 5 pens/treatment) and fed a corn-soybean meal control diet or the same diet supplemented with 1.5 g/kg green, purple, or orange colorant. Intestinal histomorphology, serum biochemical markers, and hypothalamic gene expression (NPY, AGRP, POMC, CART) were assessed at the end of trial (42 days of age). Performance criteria were also recorded during the trial. Across the growing and finishing phases, colored feeds increased feed intake and weight gain relative to the control, with the orange group consistently showing the largest effects. The largest improvement in body weight gain and feed conversion ratio (FCR) was recorded in the orange feed group, which was associated with greater improvements in villus height and absorptive surface area in different segments of the small intestine. Green feed showed intermediate benefits, improving feed intake, weight gain, and FCR over the entire trial (1-42 d) but to a lesser extent than orange, while purple feed failed to significantly improve growth performance despite showing comparable improvements in intestinal morphology. Serum cholesterol and HDL concentrations were higher in the green group compared to the control and purple groups, total protein was higher in the orange group compared to the control, and albumin was higher in both green and orange groups compared to the control and purple groups, while hepatic enzymes, MDA, NO, LDL, triglyceride, and glucose did not differ among treatments. Colored feeds stimulated appetite through up-regulation of orexigenic genes (NPY, AGRP) and down-regulation of anorexigenic genes (POMC, CART), with the purple group showing the most pronounced orexigenic gene expression despite its poorer performance. This dissociation may be partly attributed to the reduced feed lightness index of the purple diet. The results of this study could have significant potential for practical application in commercial poultry production.