Intestinal immune response in post-weaning piglets

Abstract

The process of weaning in piglets is known to change the intestinal morphology, caused by the changes in feed intake pattern, for example changing from liquid to solid feed and a decrease in intake post-weaning, and/or physiological or environmental stressors (Pluske et al., 1997). Weaning can result in high morbidity and mortality resulting from post-weaning diarrhea (McCracken et al., 1999; Lallès et al., 2004; Fairbrother et al., 2005). From a nutritional perspective, controlling early intestinal inflammation is certainly a challenge in managing post-weaning gut disorders. Preventing intestinal inflammation due to pathogenic enteric organisms can be an important pillar to maintain the health of piglets. The injudicious use of antimicrobials selects for resistant bacterial strains, imposing a risk for human and animal health (Coculescu et al., 2014; Holyoake et al., 2009; Jia et al., 2006; Mirajkar et al., 2016). The main objective of the present thesis was to investigate the intestinal inflammation response in piglets after weaning, to find new strategies that can reduce this inflammation response, which damages intestinal integrity, cause gut disorders and cost energy. Due to the need to reduce antibiotic usage in production animals and minimize risk of bacterial resistance against antibiotics, relevant strategies may focus on reducing risk of pathogenic and zoonotic bacteria in the feed-to-food chain, mitigate post-weaning diarrhea, and achieve profitable systems. To achieve this goal, the thesis contemplates different objectives: 1. Evaluate the inflammation response in piglets post-weaning systemically and locally in the different intestinal tissues, in commercial setting but with low infection pressure (as proved by low diarrhea response) 2. Evaluate the inflammation response in piglets post-weaning systemically and locally in the different intestinal tissues, caused by specific pathogen challenges using a previous described challenge method, using pathogens that are known for causing major economic losses due to poor growth performance, and increased production costs associated with treatment 3. To investigate non-antibiotic compounds with previously described antimicrobial effects that have been suggested to support gut health and reduce intestinal inflammation, as part of a nutritional strategy to modulate the complex interplay between the immune system and/or inflammatory responses and the consequences on animal health and performance. Organic acids (OA), being short chain fatty acids (SCFA) and medium chain fatty acids (MCFA), prebiotics, phytobiotics, and enzyme inhibitors are currently being explored commercially as alternatives to antimicrobials (Bindels et al., 2015; Cook & Sellin, 1998; Dibner & Buttin, 2002; Gadde et al., 2017; Gibson et al., 2017; Keyser et al., 2008; Schönfeld & Wojtczak, 2016; Tugnoli et al., 2020) Intestinal inflammation costs energy and can increase permeability and reduce digestion and growth performance in post-weaning piglets. This study shows that these effects can be prolonged, but the intestine can recover. Furthermore, non-antimicrobial additives can be supporting the intestinal health of these piglets, by reducing inflammation response and promoting intestinal integrity. This effect was also seen in disease challenges with pathogens known to cause enteropathogenic problems in swine production. Findings also suggest that non-antimicrobial compounds may have beneficial effects for the host based on an explant model data, where compounds tested supported epithelial survival, reduced mucus thickness and immune-modulating effects when explants were exposed to B. hyodysenteriae. Compounds prevented epithelial death following L. intracellularis exposure. Concluding, results of this study confirm the effect of weaning on a local and systemic level related to inflammation response and intestinal integrity. There are in feed molecules or compounds available that might support the piglets during this challenging period.