The antimicrobial alternative precursor-derived peracetic acid and zinc oxide lead to a sex dependent microbial modulation in weaning piglets

Several authors described the sexual dimorphism of the gut microbiota in pigs and other animals in relation to sex-specific modulation following interventions such as diet or prebiotics and probiotics. These differences can also influence the host phenotype through the bi-directional pathways of the microbiota-gut-brain axis and could ultimately impact an animal's welfare and well-being. Postweaning diarrhoea is a multifactorial disease that occurs in piglets and is characterised by the sudden diet change from the sow milk to solid feedstuff, with moderate to heavy diarrhoea, accompanied by decreased performance, usually BW gain. In our previous work, we described that the broad-spectrum antimicrobial-alternative peracetic acid ameliorated the diarrhetic symptoms in piglets similarly to what was observed for zinc oxide. Here, we present a further analysis of this data set, assessing the interactions between interventions and sex. A 14-day animal study was carried out, during which 28-day-old, weaned piglets were allocated to 24-floor pens with four treatments, six pens and 12 piglets per treatment, six males and six females. The four treatments were a negative control, supra-nutritional in-feed zinc oxide, and either 50 or 150 mg/kg of in-water peracetic acid. Performance and postweaning diarrhoea were assessed throughout the study, whereas at day 14, gastrointestinal content samples were collected from all the pigs to allow downstream total bacterial quantification and 16S rRNA sequencing analysis. We found that the BW gain was greater in females compared to males given zinc oxide or peracetic acid. Moreover, apart from sex-specific differences in the microbial composition, we observed that both peracetic acid and zinc oxide led to different microbial modulation in males and females. Indeed, in the stomach, Sarcina, Actinobacillus and unclassified Neisseriaceae were depleted only in males given the high peracetic acid concentration, whilst the same treatment led to the reduction of Moraxella in females. Escherichia-Shigella was reduced after zinc oxide administration, but only in females. Finally, although Lactobacillus was less abundant in males in the caecum, both zinc oxide and peracetic acid led to its increase, but only in males.