An experiment was conducted to evaluate the impact of 5% dietary treated wheat straw on the local and systemic health of nursery pigs experiencing a vaccination-induced immune challenge. Twenty-four barrows (PIC 800 x Yorkshire) were weaned at 27.7 ± 0.8 d (8.6 ± 1.2 kg) and randomly assigned to four cohorts based on weight and parentage, with six pigs per cohort. Cohorts were randomly assigned to two treatments: a control treatment (CON), which was a commercially alike standard dietary nursery program and a treated wheat straw (TWS) treatment, which was a dietary program like the CON treatment but included 5% treated wheat straw. After being fed experimental diets for 21 d, pigs were challenged with two vaccinations, the injectable Ingelvac® CircoFLEXTM Porcine Circovirus Type 2 vaccine, and an orally administered Enterisol® Lawsonia intracellularis vaccine. All pigs were sacrificed on d 42. Blood samples were collected to assess plasma IgA and iFABP concentration. Mucosal scrapings from segments of the distal ileum and ascending colon were removed for the analysis of localized immunological markers IL-6, IL-10, IL-12, and TNF-α. Serum PCV2 titers and mucosal L. intracellularis titers confirmed an active immune response to vaccination. The ascending colon of TWS treatment increased crypt depth (P = 0.05) and muscle thickness (P < 0.01). Gene expression of TWS treatment for colonic TNF-α and IL-6 (P < 0.05) were greater. Overall, nursery diets with 5% treated wheat straw impacted the health of vaccine-challenged pigs, as seen with changes in colonic morphology and the expression of immune markers. The weanling pig’s response to 5% treated wheat straw in the diet depends on the health of the pig, leaving the practice of using dietary fiber to alleviate illness associated with weaning of the pig unestablished as a recommendation across all farms.
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