Effect of Supplemental Protease on Growth Performance, Nutrient Digestibility, and Gut Health in Nursery Pigs Fed Diets with Corn or Sorghum

A total of 144 pigs (18.4 ± 2.3 kg initial BW at 6 wk of age) were used in a 40-d trial to evaluate effects of protease (300,000 U/kg feed, BioResource International. Inc., Durham, NC) on growth performance, apparent ileal digestibility (AID) of nutrients, and gut health of nursery pigs fed diets with sorghum. Pigs were randomly allotted to 4 treatments (12 pens per treatment, 3 pigs per pen) in a 2 × 2 factorial arrangement (corn or sorghum basal diet, and 0 or 0.05% protease as 2 factors) with sex and initial BW as blocks. Experimental period had phase 1 (d 1 to 21), and phase 2 (d 22 to 40). About 65 % (phase 1) and 72% (phase 2) of cereal grains were used in corn or sorghum based diets. Both cereals were ground to 400 µm. Body weight and feed intake were recorded weekly. On d 35, serum was collected to quantify tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA). On d 40, 32 pigs (8 pigs per treatment) were euthanized to collect digesta from jejunum and ileum (for viscosity and AID), tissues (for morphology) and mucosa samples (for TNF-α and MDA) from duodenum, jejunum, and ileum. Replacing corn with sorghum in the diet increased (P < 0.05) overall ADG (from 756 to 787 g/day) and ADFI (1374 to 1473 g/day), reduced (P < 0.05) overall G:F (from 0.553 to 0.537), and did not affect nutrient digestibility. Pigs fed diets with sorghum had a lower (P < 0.05) MDA content in serum (from 14.61 to 6.48 µM) and jejunum (1.42 to 0.91 µmol/g protein), and a reduced (P < 0.05) villus height (from 492 to 396 µm) and crypt depth (from 310 to 257 µm) in jejunum. Dietary protease improved (P < 0.05) AID of CP (from 81.8% to 86.0%), decreased MDA level (from 1.20 to 0.98 µmol/g protein) in duodenum, and increased (P < 0.05) ratio of villus height to crypt depth (from 1.08 to 1.21) in duodenum. Overall, use of sorghum fully replacing corn in nursery diets could be beneficial to nursery pigs with enhanced feed intake and growth of nursery pigs potentially by reducing oxidative stress. Supplementation of protease improved protein digestion and gut health, irrespective of sorghum or corn based diets.