Effects of Dietary Protease on Gut Microbiota of Weaned Pigs

This experiment was conducted to investigate effects of dietary protease on gut microbiota of weaned pigs. A total of 75 weaned pigs (7.06 ± 0.18 kg BW; 28 d old) were randomly assigned to three dietary treatments (5 pigs/pen; 5 pens/treatment) in a randomized complete block design (block = BW). The dietary treatments were 1) a diet based on corn and soybean meal to meet or exceed the requirement of crude protein as a positive control (PC; CP = 24.17%), 2) a low protein diet as a negative control (NC; CP = 23.51%), and 3) NC + 0.02% protease (PRO). The protease used in this experiment was a commercial product (Ronozyme® ProAct, DSM nutrition products, Kaiseraugst, Switzerland) containing 75,000 protease units/g derived from Bacillus licheniformis. The dietary treatments did not include spray dried plasma, fishmeal, zinc oxide, and antibiotics to avoid their antibacterial or physiological effects. Pigs were fed each treatment for 6 weeks. Three weaned pigs per dietary treatment were randomly selected to collect feces on the last day of the experiment to verify their gut microbiota by metagenomic analysis with pyrosequencing. The pyrosequencing data was analyzed using CLcommunity program. PRO increased (P < 0.05) phylum Firmicutes and genus Lactobacillus in gut microbiota of weaned pigs compared with PC or NC. However, PRO decreased (P < 0.05) phylum Bacteroidetes and genus Clostridium and Streptococcus in gut microbiota of weaned pigs compared with PC or NC. In conclusion, addition of protease in nursery diets modulated gut microbiota of weaned pigs.