Effects of dietary protease on immune responses of weaned pigs

This experiment was conducted to investigate effects of dietary protease on immune responses of weaned pigs. Weaned pigs (n = 75; 7.06 ± 0.18 kg BW; 28 d old) were randomly assigned to 3 treatments (5 pigs/pen; 5 pens/treatment). Dietary treatments were positive control, a diet with required protein level (PC), negative control, a diet with lower protein level than PC (NC), and NC + 0.02% dietary protease (PRO). The dietary protease used in this experiment was a commercial product containing 75,000 protease units/g derived from Nocardiopsis prasina produced in Bacillus licheniformis. The dietary treatments did not contain any ingredients or additives that may provide antibacterial or physiological effects. Pigs were fed respective dietary treatments for 6 weeks. Blood was collected from randomly selected 2 pigs in each pen on d 1, 3, 7, and 14 after weaning. Measurements were number of white blood cells (WBC), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), and C-reactive protein (CRP). Pigs fed PRO had lower WBC on d 7 (14.84 vs 20.42 × 10³/μL; p < 0.05) and TNF-α on d 7 (618 vs 889 pg/mL; p = 0.085) and 14 (437 vs 576 pg/mL; p = 0.069) than those fed NC, but there were no differences on WBC and TNF-α between PC and PRO. Pigs fed PRO had lower TGF-β1 on d 3 (630 vs. 1,588 and 1,396 pg/mL; p < 0.05) than those fed PC and NC. However, no differences were found on CRP among dietary treatments. In conclusion, addition of dietary protease reduced inflammatory immune responses of weaned pigs.