Effects of enzyme-treated soy oligopeptide on intestinal health, feed preference, and growth performance in nursery pigs

Objective: The objective was to evaluate the effects of replacing soybean meal (SBM) with enzyme-treated soy oligopeptide (ESO) in nursery pig diets on intestinal health, growth performance, and feed preference. Methods: In Exp. 1, 128 pigs (average 5.2 kg) were housed in pens (4 pigs/pen), assigned to 4 diets supplemented with 0%, 1%, 2%, or 3% of ESO, and fed for 32 d. On d 32, blood, tissues, and mucosa from the duodenum and jejunum were collected. In Exp. 2, 24 pigs (average 6.2 kg) were assigned to 6 pens (4 pigs/pen). Each pen had two separate feeders containing two diets with 0% or 2% of ESO for 27 d. Results: Increasing dietary ESO tended to quadratically change serum tumor necrosis factor-α (p = 0.059; minimum at 1.6% of ESO) and duodenal villus height to crypt depth ratio (p = 0.062; maximum at 1.8% of ESO). Increasing dietary ESO linearly reduced feed intake both linearly and quadratically (p<0.05) during phase 2 (maximum at 0.9% of ESO). Increasing dietary ESO both linearly and quadratically changed (p<0.05) weight gain during phase 2 (maximum at 1.0% of ESO). Increasing dietary ESO linearly changed (p<0.05) and tended to quadratically change (p = 0.077) weight gain during the overall phase. Increasing dietary ESO tended to linearly change (p = 0.059) gain to feed ratio during phase 1 and quadratically change (p<0.05) gain to feed ratio during phase 2 (maximum at 1.4% of ESO). Feed preference of the diet containing 2% of ESO was negatively associated with post-weaning days (R2 = 0.542). Conclusion: Gradually replacing SBM with ESO at levels from 1.4% to 1.8% enhanced intestinal health and gain to feed ratio, whereas exceeding 0.9% to 1.0% reduced feed intake and weight gain, suggesting that optimal level of ESO in nursery pig diets is 0.9%.