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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #425987
Research Project: Physiological, Microbiological, and Nutritional Mechanisms to Maintain Animal Productivity in the Absence of Antibiotics

Location: Agroecosystems Management Research

Title: Evaluation of dietary crude protein and non-starch polysaccharidase on nursery pig performance, nitrogen retention, hindgut fermentation and health

Author
item NISLEY, MITCHELL - Iowa State University
item Kerr, Brian
item Pearce, Sarah
item SPARKS, JOSEPH - Iowa State University
item GABLER, NICHOLAS - Iowa State University

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2026
Publication Date: 7/2/2026
Citation: Nisley, M.J., Kerr, B.J., Pearce, S.C., Sparks, J.C., Gabler, N.K. 2026. Evaluation of dietary crude protein and non-starch polysaccharidase on nursery pig performance, nitrogen retention, hindgut fermentation and health. Translational Animal Science. https://doi.org/10.1093/tas/txag090.
DOI: https://doi.org/10.1093/tas/txag090

Interpretive Summary: Compared to low crude protein diets, high crude protein fed to nursery pigs is thought to antagonize intestinal health which may result in reduced growth performance. Research on this topic, however, has shown varied results and it is unclear whether changing protein levels causes notable changes in pig growth and health parameters. A high crude protein versus a low crude protein diet was fed to young pigs to assess factors associated with performance and intestinal health. The data show that pigs fed the high crude protein diets showed increased stool looseness and increased growth rates. Increased consumption of high crude protein diets did, however, result in increased nitrogen excretion. This data is valuable to the swine industry, nutritionists and producers, showing that higher levels of dietary crude protein may increase stool looseness and animal performance, but it may increase nitrogen excretion into the environment.

Technical Abstract: Reducing total dietary crude protein in nursery pig diet formulation has been a strategy to decrease post weaning diarrhea (PWD), optimize feed costs, and reduce environmental nitrogen excretion. The mechanisms postulated by which high crude protein diets increase PWD involve potentially cytotoxic proteolytic fermentation metabolites produced in the hindgut from unabsorbed peptides and amino acids. To attenuate the latter mechanism, the dietary fiber inclusion is increased to alter the primary substrate of fermentation for resident microbiota. Thus, the assessed high and low CP diets in conjunction with a novel non-starch polysaccharidase (NSPase) in a 3 x 2 factorial design on performance, nitrogen retention, hindgut fermentation and health markers in nursery pigs. A total of 792 newly weaned 17 to 22- day-old mixed sex pigs were randomly allotted to three CP diets with or without NSPase (12 pens/treatment), fed in three phases (10, 11, and 21 days). The CP and lysine (Lys) per diet and phase were: 1) 17% CP containing (1.40, 1.35, and 1.30% standardized ileal digestible (SID) Lys (LCP1.4)); 2) CP 24% containing (1.40, 1.35, and 1.30% SID Lys (HCP1.4)); 3) 17% CP containing (1.20, 1.15, and 1.10% SID Lys per phase (LCP1.2)). On d 10, one barrow per pen were moved to metabolism crates and fed at 90% ad libitum for 7 d on phase 2 diets, where after total fecal and urine output were collected over a 4-d period for nitrogen retention analysis (12 pigs/treatment). On d 22, pigs utilized for metabolism evaluation were euthanized to collect ileal and colonic tissue for morphology assessments. Colon luminal content were collected for bioamine and volatile fatty acid (VFA) analysis. Both ADG and feed efficiency were highest in HCP1.4 fed pigs in all phases and overall (P<0.01). Overall HCP1.4 fed pegs observed increased PWD incidence compared to LCP1.4 and LCP1.2 fed pigs (P<0.01). Neither CP level nor NSPase inclusion significantly impacted gut morphology (P>0.10). High CP fed pigs observed increased nitrogen excretion and retention when compared to both LCP treatments (P<0.01). Crude protein content did not impact production of key bioamines cadaverine and putrescine (P>0.10). Pigs fed HCP1.4 elicited the highest production of total VFAs (P<0.05). Herein, pigs fed HCP diets observed improved performance concurrently with increased stool looseness, and our results further corroborate with prior research correlating CP intake with nitrogen excretion.