The influence of the genetic background and feeding strategies on the health, performance and gastrointestinal homeostasis of weaned pigs

In pig intensive production system, weaning is generally considered the most stressful phase and represents a main challenge. Piglets have to face several stress factors that coupled with the lack of a complete immune competence contribute to the occurrence of post-weaning diarrhoea (PWD) syndrome mainly supported by enterotoxigenic Escherichia coli (ETEC) F4 and F18. In this phase, the host-microbial interplay plays a key role and it can be influenced both by external (i.e. diet) and internal (i.e. age, sex and genetics) factors. The present thesis reports three studies focused on genetic and feeding strategies influences on the host-microbial interplay in weaned pig through the application of new omics approach. The first study demonstrates that the pigs' Mucine 4 (MUC4) genotype (DQ848681:g.8227C>G), previously associated with ETEC F4ac susceptibility, influences the degree of jejunum fucosylation, the expression of genes involved in the intestinal homeostasis and the blood metabolic profile of healthy piglets. The first and the second studies showed that the pigs' Alpha (1,2)-fucosyltransferase (FUT1) genotype (M307 A>G), previously associated to ETEC F18 susceptibility, affects the intestinal fucosylation, the jejunal microbial balance by increasing the non-beneficial bacteria in susceptible genotypes and the blood metabolic profile of healthy piglets during pre and post-weaning. The third study evaluates the effectiveness of Saccharomyces cerevisiae (Sc) supplementation (5x1010 CFU/kg) to counteract the ETEC F4ac infection in MUC4 susceptible weaned pigs. MUC4 genotype confirmed its efficacy as a marker for ETEC F4ac susceptibility. The preventive and competitive supplementation of Sc was effective in containing the ETEC F4ac infection as showed by jejunal transcriptomic profile. The thesis provides new insight on the interplay between host-genetics, gut microbiota and host physiological status. Furthermore, it highlights that known genetic markers for ETEC F4 and F18 could be applied to stratify the animals in trials both in healthy or challenge-based protocols.