Peracetic acid to replace zinc oxide, modulating microbiota to control pig post-weaning diarrhoea

Application
In-water peracetic acid (PAA, CH3CO3H), derived by the hydrolysis of sodium percarbonate (SP) and tetraacetylenediamine (TAED) could replace zinc oxide (ZnO), controlling pig post-weaning diarrhoea via microbiota modulations.

Introduction
ZnO has been widely used to alleviate weaning-diarrhoea symptoms (Ou et al., 2007), however it has recently faced a ban due to environmental pollution. SP/TAED-derived in-water PAA is a broad-spectrum antimicrobial-alternative with proven efficacy in poultry (Galgano et al., 2021). In this study, we tested the PAA potential towards post-weaning diarrhoea compared to ZnO.

Materials and methods
Four treatments, control, in-feed ZnO (3100 ppm), 50 ppm and 150 ppm of PAA, were administered to 6 pens/treatment (14-day trial) with 2 pigs per pen and 6 rooms (4 pens/room). In-water PAA treatments were prepared daily, mixing different ratios of SP and TAED. We measured faecal scores/performance, and microbial composition via 16S rRNA sequencing (515Fb-816Rb) of DNA from stomach, ileum and caecum. Linear mixed model was carried out in R with lme4 for performance and MaAsLin2 for taxonomical data, including fixed (treatment) and random effects (rooms/pens/pigs), β-diversity was analysed via PERMANOVA.

Results
Lower faecal score, linked to improved diarrhoea was found in the ZnO group at day-7 (1.26 ± 0.2) compared to control (1.52 ± 0.1, P < 0.05), whilst day-14 diarrhoea improved in 150 ppm (1.57 ± 0.44, P = 0.05), ZnO and 50 ppm (1.36 ± 0.26 1.57 ± 0.31, P < 0.05) compared to control (1.8 ± 0.37).

Bray-Curtis dissimilarity analysis showed different caecal microbial composition in the control group, compared to 50 ppm, 150 ppm and ZnO (P < 0.05, Q < 0.05). The same analysis showed that 50 ppm and 150 ppm had similar caecal composition, which was however different from ZnO (P < 0.05, Q < 0.05). Stomach Campylobacter was reduced in 150 ppm, ZnO (P < 0.05, Q < 0.05), and 50 ppm (P < 0.05, Q = 0.161) compared to control. ∼20 caecal genera were differentially abundant, e.g., Ruminococcus, Oribacterium reduced were in ZnO compared to control (P < 0.05, Q < 0.05).

Conclusions
We found that both PAA and ZnO improved the faecal scores. PAA and ZnO reduced stomach Campylobacter, linked to post-weaning diarrhoea (Adhikari et al., 2019). Ruminococcus and Oribacterium, linked with better performance (Uryu et al., 2020) were only reduced in ZnO.