Effects of dietary protein level on intestinal function and inflammation in nursery pigs

Authors: Pearce, Sarah; NISLEY, MITCHELL - Iowa State University; Kerr, Brian; SPARKS, JOSEPH - Huvepharma Inc; GABLER, NICHOLAS - Iowa State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2024
Publication Date: 3/20/2024
Citation: Pearce, S.C., Nisley, M.J., Kerr, B.J., Sparks, C., Gabler, N.K. 2024. Effects of dietary protein level on intestinal function and inflammation in nursery pigs. Journal of Animal Science. 102. Article skae077. https://doi.org/10.1093/jas/skae077.
DOI: https://doi.org/10.1093/jas/skae077

Interpretive Summary: High dietary crude protein is thought to antagonize nursery pig intestinal health including causing diarrhea in young pigs. Low crude protein diets may also provide a potential cost saving in diet formulations depending upon ingredient and crystalline amino acid costs. However, research on this topic has shown varied results and it is unclear whether changing protein levels causes notable changes in pig health. A high crude protein versus a low crude protein diet was fed to young pigs with factors associated with intestinal health and inflammation being evaluated. In this study, feeding high crude protein diets to nursery pigs did not negatively intestinal health, especially in the large intestine and it only had a minor effect on inflammation. Overall conclusions of our study show that protein level in the diet has little impact overall on animal health and performance. This data is valuable to the soybean industry, farmers and soybean crushers, and to the swine industry, nutritionists and producers, showing that higher levels of dietary crude protein provided by soybean meal has little impact on animal health and overall performance parameters.

Technical Abstract: High crude protein (21-26%) diets fed during the first 21-28 days post-weaning are viewed negatively because of a perceived increase in the incidence rates of diarrhea due to increased intestinal protein fermentation and/or augmented enteric pathogen burden. This is thought to antagonize nursery pig health and growth performance. Therefore, our objectives were to evaluate the impact of low vs. high dietary crude protein on 21 day post weaned pig intestinal function and pig performance. Analyzed parameters included ex vivo intestinal barrier integrity (ileum and colon), ileal nutrient transport, tissue inflammation, and fecal dry matter. Gilts and barrows (n = 6/trt) were randomly assigned to one of two diets post-weaning. Diets were fed for 21 d, in 2 phases. Phase 1 diets: Low crude protein (17%) with a 1.4% standard ileal digestibility (SID) Lysine (LCP), or high crude protein (24%) with a1.4% SID Lysine (HCP). Phase 2: LCP (17%) and a 1.35% SID Lysine, or HCP (24%) formulated to a 1.35% SID Lysine. Pig growth rates, feed intakes and fecal consistency did not differ (P>0.05). There were no differences in colonic epithelial barrier function as measured by transepithelial electrical resistance and FITC-dextran transport between treatments (P>0.05). IL-1A, IL-1B, IL-1ra, IL-2 IL-4, IL-6 and IL-12 were not different between treatments (P>0.05). However, IL-8 and IL-18 were higher in HCP-vs. LCP-fed pigs (P<0.05). There were no differences in fecal dry matter (P>0.05) between treatments. In the ileum, there was a tendency (P=0.06) for TER to be higher in HCP-fed pigs, suggesting a more robust barrier. Interestingly, glucose and glutamine transport were decreased in HCP vs. LCP-fed pigs (P<0.05). FITC-Dextran transport was not different between treatments (P value). There were also no differences in ileal cytokine concentrations between diets (P>0.05). Taken together, this data shows that low crude protein does not negatively impact colonic barrier function, fecal dry matter, or inflammation. In contrast, ileal barrier function and nutrient transport were altered, suggesting a regional effect of diet on overall intestinal ‘function’.