# Impact of low-crude protein and insoluble fiber diets on post-weaning diarrhea, growth performance, intestinal morphology, and gene expression for nursery pigs with natural rotavirus and subject to enterotoxigenic Escherichia coli F18+ experimental infection

## TL;DR

This study found that low-protein or fiber-rich diets in young pigs did not reduce diarrhea or improve recovery from gut infections compared to traditional diets with zinc and antibiotics.

## Contribution

The study evaluates the effectiveness of low-protein and fiber diets in mitigating post-weaning gut issues in pigs infected with rotavirus and ETEC.

## Key findings

- Low-protein and fiber diets did not reduce scour scores or improve recovery from infections compared to traditional diets.
- The PC diet (with zinc oxide and carbadox) significantly reduced scour scores during infections.
- LCP and FIB diets lowered TNFα levels but did not translate into biological benefits.

## Abstract

This study evaluated the impact of low‑crude protein (LCP) and insoluble fiber (FIB) diets on post‑weaning diarrhea, intestinal damage, and growth in nursery pigs naturally infected with rotavirus and challenged with enterotoxigenic Escherichia coli F18 (ETEC). A total of 240 pigs were randomly assigned to 40 pens (6 pigs/pen) for a 42-d experiment. Pens were randomly assigned to one of five diets: NC (standard nursery diet without zinc oxide, ZnO, or carbadox); PC (NC + 3,750 mg/kg ZnO and 50 mg/kg carbadox); LCP (NC with reduced crude protein and SID Lys); FIB (NC + 8% wheat middlings); and ZINC (NC + 3,750 mg/kg ZnO). Experimental diets were fed in two phases: phase 1 (d 0–7) and phase 2 (d 7–21) and phase 3 (d 21–42) was a common diet for all pigs. Pigs were positive for rotavirus (strains A, B, and C) within the first week post-wean. To model late nursery outbreaks, pigs were orally inoculated with a field strain of ETEC on day 14-, or 0-d post-inoculation (DPI 0). Scour scores were recorded daily for the first 28 d (−14 to 14 DPI). Body weight (BW), average daily gain (ADG), feed disappearance (ADFI), and feed efficiency (G: F) were evaluated for four periods: DPI −14 to −7; −7 to 0; 0 to 7; 7 to 28. Sample pigs were confirmed to be susceptible to ETEC (FUT1GG/GA). Serum TNFα was measured at DPI 0, 3 and 6. Ileal and colonic tissues and colonic digesta were collected from two pigs per pen, euthanized on DPI 3 and 6. Fecal swabs (one/pen) were collected on DPI 0, 2, 4, 6, and 14 to assess shedding of ETEC F18 and STb genomic material. Data were analyzed using mixed model methods (SAS 9.4, Cary, NC) with pen as the experimental unit with the fixed effects of diet, period, and their interaction. Overall growth metrics were unaffected by dietary treatment. Rotavirus and ETEC inoculation increased scour scores, and F18/STb genomic material was detected in feces after inoculation. The PC diet reduced scour scores during both rotavirus and ETEC infections (P < 0.01). Ileal morphology and gene expression improved from DPI 3 to 6 (P < 0.05), independent of diet (P > 0.1). Colonic morphology, inflammation, and putrescine and cadaverine levels were unaffected by diet (P > 0.1). Although LCP and FIB diets lowered circulating TNFα at DPI 0 and 6, these reductions did not translate into measurable biological benefits. Compared with the PC diet, the LCP and FIB diets were ineffective in improving outcomes of the enteric challenge in this study.

Young pigs fed low-protein or fiber-rich diets after weaning didn’t show less diarrhea or faster recovery from gut infections compared to pigs fed a traditional diet with zinc and antibiotics. These findings suggest that such alternative diets may not provide enough protection or support during common post-weaning health challenges.