Impact of dietary protease supplementation on broiler performance and gas emissions: A meta-analysis

This meta-analysis investigated the impact of protease supplementation on growth performance and gas emissions in broiler diets. A total of 145 individual trials, comprising 852 data points, were included. The results revealed a significant decrease in the feed conversion ratio (FCR), and improvements in body weight gain (BWG) and body weight (BW) due to protease supplementation. The effect sizes were -0.374 (SE=0.029; P<0.001) for FCR, 0.440 (SE=0.031; P<0.001) for BWG, and 0.370 (SE=0.056; P<0.001) for BW. Subgroup analysis revealed greater effectiveness in diets containing up to 21% crude protein and diverse ingredient compositions. However, no significant reduction in ammonia (NH3), hydrogen sulfide (H2S), or methyl mercaptan (CH3SH) emissions was observed. This study revealed that protease supplementation improved broiler growth performance but had a limited impact on gas emissions. Future studies should explore integrating protease supplementation with other synergistic interventions that could have a greater impact on reducing gas emissions.