Young Scholar Presentation: How Is Pig Intestinal Function and Health Altered in Response to Pathogen Challenges?

In recent years, gut health has been heavily discussed, yet ambiguously defined in terms of pig production. In a review article, Celi et al. (2017) defined gut health as “a steady state where the microbiome and the intestinal tract exist in symbiotic equilibrium and where the welfare and performance of the animal is not constrained by intestinal dysfunction.” Intestinal function is therefore multifaceted and in addition to microbiota, should include host secretory, absorptive, structural, and immune parameters. These should all be considered as they collectively play a role in pig welfare and performance, especially during a pathogen challenges. Pathogen challenges can be categorized based on their mode of action (i.e. enteric or systemic) and thus may influence intestinal function differently. We have shown that porcine epidemic diarrhea virus (PEDV), an enteric pathogen, has a negative impact on intestinal integrity and function in 5-week-old pigs. At day post inoculation (dpi) 5, pigs inoculated with PEDV had reduced (P < 0.05), villus height, transepithelial resistance (TER), immunohistochemistry (IHC) stain intensity for tight junction proteins Claudin 2 and 4, and digestive function in the jejunum compared with naïve counterparts. However, pigs inoculated with PEDV were relatively quick to recover. By dpi 7, the virus was no longer detected by IHC in the jejunum of PEDV inoculated pigs and they had returned to levels of naïve counterparts for the aforementioned measurements. Interestingly, there were lasting impacts of PEDV infection on mucin composition within goblet cells in the jejunum. Pigs inoculated with PEDV had reduced (P < 0.05) total acidic mucin at dpi 2, but increased (P < 0.05) total acidic mucin by dpi 14 compared with naïve counterparts and this was driven primarily by increased sialomucin. How changes in mucin composition within goblet cells relates to secreted mucin and possible susceptibility to secondary infections has yet to be determined. Although in these studies, PEDV was relatively quick to be cleared from the jejunum (by dpi 7), PEDV infection is dependent on several factors including age, virulence, dose, health status, etc. Regardless, this enteric pathogen infection resulted in reduced growth performance, intestinal integrity and function, and increases days to market, ultimately reducing producer profitability. Although research has primarily been focused on peak infection of pathogen challenges, it is important to understand resolution and long-lasting impacts of these pathogen challenges on pig health and performance.