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

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 in piglets at different weaning ages. 48 piglets were divided into four groups weaned at 14, 21, 28 and 42 days old (late weaning). In each group, faecal bacteria composition was assessed by sequencing the 16S rRNA gene 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. The pre-weaning gut microbiota composition conferred by a late weaning at 42 days of age could enhance gut health in piglets. 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. 71 piglets were divided into three groups: two groups differing by amoxicillin administration routes – parenteral or oral, and a control group without antibiotics. Our results confirmed the MUC4 and FUT1 as host genetic markers for the susceptibility to ETEC infections. Moreover, 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 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.