Dietary bile acid supplementation influences protein digestibility and alters plasma amino acid profiles in broiler chickens fed conventional and reduced-protein diets

Abstract

Reduced crude protein (CP) diets based on wheat have been shown to lower body weight (BW), increase feed conversion ratio (FCR), and elevate fat-pad deposition in broiler chickens. Bile acids facilitate lipid digestion and nutrient absorption by emulsifying fats and promoting micelle formation in the intestine. Therefore, it was hypnotized that supplementing reduced CP diets with bile acids may enhance fat utilization, improve energy efficiency, and mitigate the negative effects of low-CP diets on broiler performance and nutrient digestibility. Four dietary treatments were arranged in a 2 × 2 factorial layout, with two CP levels (standard and a 30 g/kg CP reduction), with or without 0.2 g/kg bile acids. A total of 840 off-sex male Ross 308 chicks were randomly assigned into 24 floor pens, with six replicates of 35 birds per treatment. From 0 to 42 days post-hatch, there was no interaction between dietary CP and bile acids supplementation for BW, feed intake (FI), FCR, abdominal fat pad, and nutrient digestibility (P > 0.05). As a main effect, reducing dietary CP decreased BW, FI, fat digestibility, and increased FCR and abdominal fat pad (P < 0.01). The reduced CP diet resulted in lower plasma concentrations of valine, isoleucine, arginine, histidine, phenylalanine, leucine, and tryptophan, while increasing lysine, methionine, and threonine concentrations (P < 0.01). Bile acids supplementation enhanced dry matter and protein digestibility (P < 0.05). Bile acids also showed a tendency to increase plasma methionine concentrations (P = 0.055). A significant interaction effect was observed for overall mortality, with bile acids supplementation reducing mortality in birds fed reduced CP diets (P < 0.01). These findings suggest that in reduced CP diets, the current ideal AA profile may be deficient in arginine and histidine, potentially contributing to increased fat pad weight. Elevated wheat-derived non-starch polysaccharide concentrations might lower fat digestibility in reduced CP diets. Supplementation of bile acids in these diets could mitigate endogenous taurine losses and improve overall health in broiler chickens.