Influence of dietary protease supplementation to high- and low-protein diets on growth performance, nutrient digestibility, blood profiles, and gas emissions in finishing pigs

A total of 160 growing pigs (Duroc × (Landrace × Yorkshire); 54.11 ± 2.81 kg)) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial design with two different levels of crude protein (CP) (15% or 13%) with or without 0.025% protease for 10 weeks. Each treatment had eight replicates with five pigs (three gilts and two barrows) per pen. During the overall experimental period, pigs fed a high CP diet supplemented with 0.025% protease showed significantly higher ( P < 0.05) daily gain and reduced gain-to-feed ratio compared to those fed low CP diet without protease. Moreover, at the end of week 10, pigs in the protease-treated group exhibited significantly increased ( P < 0.05) BW, apparent total tract digestibility of nitrogen and energy, and significantly reduced ammonia emission. Furthermore, glucose, blood urea nitrogen, and creatinine concentrations were significantly increased ( P < 0.05) in pigs fed a high CP diet supplemented with protease. These findings suggest that incorporating 0.025% protease into high CP diets may serve as an effective strategy to enhance the growth and overall performance of pigs while potentially mitigating environmental nitrogen emissions.