Effects of partial replacement of soybean meal in broiler diets with gelatin and mono-component protease on growth performance, carcass and blood biochemical characteristics, lipid oxidation of meat, and economics

Context. Gelatin, presently a waste material from animal tissues and bones, may be suitable as a partial dietary replacement for soybean meal. In combination with protease, it may enhance growth performances of broiler chickens. However, limitations when introducing gelatin, are its unusual amino acid profile and digesta viscosity. Aim. An experiment was conducted to elucidate effects on growth performance, blood biochemistry, carcass and meat characteristics, and feed costs of partial replacement of soybean meal with gelatin and protease in broilers diets. Methods. The experimental design was a factorial arrangement of two levels of mono-component protease (0 and 200 g/t diet) and four levels of gelatin (0%, 2.82%, 4.23% and 5.64% of the diet) with six replicates and 15 male broiler chickens in each pen. Key results. The higher levels of gelatin inclusion decreased bodyweight and increased feed conversion ratio (P < 0.001), whereas addition of enzyme improved both parameters (P < 0.001). Higher gelatin inclusion levels decreased abdominal fat, and enzyme addition resulted in greater carcass yield (P < 0.001). European performance efficiency factor reduced with incremental gelatin levels but increased with enzyme inclusion (P < 0.001). Feed cost per bird was reduced at higher gelatin inclusion levels, more so in the protease-treated diets up to 4.23% inclusion level. Lipid peroxidation values for breast and thigh meat decreased significantly with gelatin inclusion in the absence of protease but increased in the presence of protease. Breast and thigh lipid peroxidation was reduced (P < 0.001) by supplementation of protease in the control diet. Conclusions. The results suggest that the performance-depressing effects of gelatin can be overcome to some extent by inclusion of a protease. Implications The use of gelatin may reduce dependence on soybean meal and reduce costs by using what is at present a waste material. Consideration is needed of the digestible amino acid profile of gelatin, and choice of more effective enzymes to reduce deleterious effects of gelatin.