Brachyspira hyodysenteriae is an etiological agent of swine dysentery (SD). Diet fermentability plays a role in development of SD, but the mechanism(s) of action are largely unknown. Thus, this study aimed to determine whether replacing lowly fermentable fiber with highly fermentable fiber would mitigate a 42 d B. hyodysenteriae challenge. Thirty-nine barrows were allocated to dietary treatment groups: (1) 20% corn distillers dried grain with solubles (DDGS), 0% beet pulp (BP) or resistant starch (RS; lowly fermentable fiber (LFF)); (2) 10% DDGS, 5% BP, 5% RS (medium fermentable fiber (MFF)); and (3) 0% DDGS, 10% BP, 10% RS (highly fermentable fiber (HFF)). On day post inoculation 0, pigs were inoculated with B. hyodysenteriae. Overall, 85% LFF pigs developed clinical SD, 46% of MFF pigs developed SD, and 15% of HFF pigs developed SD (p < 0.05). Overall average daily gain (ADG) differed among all treatments (p < 0.001), with LFF pigs having the lowest ADG. For HFF pigs, ADG was 37% greater than LFF pigs (p < 0.001) and 19% greater than MFF pigs (p = 0.037). The LFF diet had greater relative abundance of Shuttleworthia and Ruminococcus torques. Further, microbiota of pigs that developed SD had enriched Prevotellaceae. Collectively, replacing DDGS with highly fermentable fiber reduced clinical SD, improved performance, and modulated fecal microbiota during B. hyodysenteriae challenge.

Antibiotics have been used for over 60 years by the swine industry to improve growth performance and feed efficiency. With rising concerns over antimicrobial resistance and government restrictions such as the Veterinary Feed Directive on usage of in-feed antibiotics, alternatives to feeding antibiotic growth promoters (AGPs) to nursery pigs are needed. However, the mechanism of action by which AGPs work is poorly understood. Thus, the objective of this study was to investigate the mechanisms of action by which AGPs increase nursery pig performance. Over two replicates, 24 weaned pigs (6.75 ± 0.75 kg body weight) were randomly allotted to either control (CON, n = 12) or sub-therapeutic antibiotic (sCTC, n = 12) treatments and housed individually. A 2-phase corn-soybean-based nursery diet was fed, with the sCTC diets containing 40 ppm feed-grade chlortetracycline. Individual pig average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) were calculated weekly for 5 weeks. Thereafter, all pigs were euthanized and necropsied for tissue collection. The overall performance data indicated that sCTC pigs had increased ADG (0.43 vs. 0.32 kg/d, P = 0.001) and ADFI (0.51 vs. 0.37 kg/d, P = 0.002) compared with CON pigs; however, G:F was not different as a result of dietary treatment (0.85 vs. 0.88, P = 0.617). Intestinal barrier permeability, ileal active nutrient transport, and cecal short chain fatty acid concentrations did not differ (P > 0.10) due to dietary treatment, however changes in several ileum mRNA transcripts suggest that inflammation may be reduced in sCTC pigs. Further, the changes observed in the proteomes of the ileum, colon, skeletal muscle, and liver suggest that the sub-therapeutic mode of action of AGPs may include post-absorptive changes and warrants further investigation.

Pathogen challenges are often accompanied by reductions in feed intake, making it difficult to differentiate impacts of reduced feed intake from impacts of pathogen on various response parameters. Therefore, the objective of this study was to determine the impact of Porcine Reproductive and Respiratory Syndrome virus (PRRSV) and feed intake on parameters of jejunal function and integrity in growing pigs. Twenty-four pigs (11.34 ± 1.54 kg BW) were randomly selected and allotted to 1 of 3 treatments (n = 8 pigs/treatment): 1) PRRSV naïve, ad libitum fed (Ad), 2) PRRSV-inoculated, ad libitum fed (PRRS+), and 3) PRRSV naïve, pair-fed to the PRRS+ pigs’ daily feed intake (PF). At 17 days post inoculation, all pigs were euthanized and the jejunum was collected for analysis. At days post inoculation 17, PRRS+ and PF pigs had decreased (P < 0.05) transepithelial resistance compared with Ad pigs; whereas fluorescein isothiocyanate-dextran 4 kDa permeability was not different among treatments. Active glucose transport was increased (P < 0.05) in PRRS+ and PF pigs compared with Ad pigs. Brush border carbohydrase activity was reduced in PRRS+ pigs compared with PF pigs for lactase (55%; P = 0.015), sucrase (37%; P = 0.002), and maltase (30%; P = 0.015). For all three carbohydrases, Ad pigs had activities intermediate that of PRRS+ and PF pigs. The mRNA abundance of the tight junction proteins claudin 2, claudin 3, claudin 4, occludin, and zonula occludens-1 were reduced in PRRS+ pigs compared with Ad pigs; however, neither the total protein abundance nor the cellular compartmentalization of these tight junction proteins differed among treatments. Taken together, this study demonstrates that the changes that occur to intestinal epithelium structure, function, and integrity during a systemic PRRSV challenge can be partially explained by reductions in feed intake. Further, long term adaptation to PRRSV challenge and caloric restriction does reduce intestinal transepithelial resistance but does not appear to reduce the integrity of tight junction protein complexes.

Lawsonia intracellularisis endemic to swine herds worldwide, however much is still unknown regarding its impact on intestinal function. Thus, this study aimed to characterize the impact ofL. intracellularison digestive function, and how vaccination mitigates these impacts. Thirty-sixL. intracellularisnegative barrows were assigned to treatment groups (n = 12/trt): (1) nonvaccinated,L. intracellularisnegative (NC); (2) nonvaccinated,L intracellularischallenged (PC); and (3)L. intracellularischallenged, vaccinated (Enterisol^®Ileitis, Boehringer Ingelheim) 7 weeks pre-challenge (VAC). On days post-inoculation (dpi) 0 PC and VAC pigs were inoculated withL. intracellularis. From dpi 19–21 fecal samples were collected for apparent total tract digestibility (ATTD) and at dpi 21, pigs were euthanized for sample collection. Post-inoculation, ADG was reduced in PC pigs compared with NC (41%,P < 0.001) and VAC (25%,P < 0.001) pigs. Ileal gross lesion severity was greater in PC pigs compared with NC (P = 0.003) and VAC (P = 0.018) pigs. Dry matter, organic matter, nitrogen, and energy ATTD were reduced in PC pigs compared with NC pigs (P ≤ 0.001 for all). RNAscope in situ hybridization revealed abolition of sucrase-isomaltase transcript in the ileum of PC pigs compared with NC and VAC pigs (P < 0.01). Conversely, abundance of stem cell signaling markers Wnt3, Hes1, and p27^Kip1were increased in PC pigs compared with NC pigs (P ≤ 0.085). Taken together, these data demonstrate that reduced digestibility duringL. intracellularischallenge is partially driven by abolition of digestive machinery in lesioned tissue. Further, vaccination mitigated several of these effects, likely from lower bacterial burden and reduced disease severity.