Effects of low protein diets added with protease on growth performance, nutrient digestibility of weaned piglets and growing-finishing pigs

The objective of this study was to evaluate effects of low protein diets added with protease on growth performance, nutrient digestibility, and blood profiles of weaned piglets and growing-finishing pigs. A total of 96 weaned pigs [(Yorkshire × Landrace) ×Duroc] with an average body weight (BW) of 6.99 ± 0.21 kg were used in a 20-week experiment. The dietary treatments were arranged in a 2×3 factorial design with two levels of crude protein (CP) and three levels of protease (PT). Pigs were allotted to one of six dietary treatment groups in a completely randomized block design based on initial BW. There were four pigs in a pen with four replicate pens for each treatment. At 4 weeks and 20 weeks after treatment, BW was higher (p < 0.05) in PT2 group than in PT0 group. From weeks 0 to 4, average daily gain (ADG) and feed efficiency (G/F) ratio were higher (p = 0.006 and p = 0.014; p = 0.014 and p = 0.044, respectively) for PT2 group than for PT0 and PT1 groups of pigs. From weeks 16 to 20, ADG and G/F ratio were higher (p < 0.001 and p = 0.009; p = 0.004 and p = 0.033, respectively) for PT2 group than for PT0 and PT1 groups of pigs. Throughout the experiment (from weeks 0 to 20), ADG and G/F ratio were higher (p = 0.044 and p = 0.049, respectively) for PT2 group than for PT0 group of pigs. CP digestibility was higher for low protein (LP) group of pigs than for high protein (HP) group at weeks 4, 12, and 20 (p = 0.013, p = 0.014, and p = 0.035, respectively). Supplementation with protease did not significantly affect CP digestibility. At weeks 4 and 20, LP diet group of pigs had lower blood urea nitrogen (BUN) levels than HP diet group of pigs (p < 0.001 and p = 0.001, respectively). Therefore, low CP diet added with protease could increase growth performance and CP digestibility of weaned piglets and growing-finishing pigs.