Enteric disorders at weaning : age, amoxicillin administration and Enterotoxigenic Escherichia coli infection affecting the gut microbiota of piglets

Abstract

In pig production systems, weaning is a crucial period characterized by nutritional, environmental and social stress. During this process, piglets are susceptible to diarrhoea and the gut ecosystem needs to adapt to dietary changes, from a milk-based diet to a solid and more complex cereal-based feed, and to environmental pathogen pressure. One of the most important etiological agent of the post-weaning diarrhoea (PWD) is the Enterotoxigenic Escherichia coli (ETEC) able to cause severe outcomes and considerable economic losses to farmers worldwide. A role of host genetics in infection appearance is well-established, the SNPs located on the Mucine 4 (MUC4) and Fucosyltransferase 1 (FUT1) genes being associated with the susceptibility to ETEC F4 and ETEC F18, respectively.To investigate aspects related to weaning diarrhoea, two studies have been performed. The aim of the first study was to evaluate the impact of weaning age on gut microbiota diversification in piglets comparing animals at different weaning ages. Forty-eight Large White piglets were divided into four groups of 12 animals weaned at 14 days old (early weaning), 21 or 28 days old (main weaning ages in pig intensive farming) and 42 days old (late weaning). In each group, faecal bacteria composition was assessed by sequencing the 16S rRNA gene of faecal DNA on the weaning day, 7 days post-weaning and at 60 days of age. Our results showed that late weaning increases the gut microbiota diversity including a higher abundance of Faecalibacterium prausnitzii, reported as beneficial in humans. Our results suggest than the pre-weaning gut microbiota composition conferred by a late weaning at 42 days of age could enhance gut health in piglets. This would provide a competitive advantage to piglets accumulating a higher diversity of potentially beneficial microbes prior to the stressful and risky weaning transition.The aim of the second study was to evaluate the effects of the host-genotype and different routes of amoxicillin administration on the presence of diarrhoea and the microbiota composition, during a natural infection by multi-resistant ETEC strains in weaned piglets. For this purpose, seventy-one piglets were divided into three groups: two groups differing by amoxicillin administration routes – parenteral (P) or oral (O) and a control group without antibiotics (C). Our results confirmed the MUC4 and FUT1 as host genetic markers for the susceptibility to ETEC infections. Moreover, our data highlighted that amoxicillin treatment may produce adverse outcomes on pig health in course of multi-resistant ETEC infection and this effect is stronger when the antibiotic is orally administered than parenterally.Both studies highlighted the importance of alternative control measures related to farm management in controlling weaning related diarrhoea. With a need to limit the use of antibiotics, selection of resistant genotypes, next-generation probiotics supplementation in feed, and correct procedures of weaning age, should be considered in farm management practices in order to preserve a balanced and stable gut microbiota and consequently reduce occurrence of diarrhoea at weaning.