PSI-17 - Effect of timing of high dietary zinc supplementation on the microbiome of gestating sows and their piglets

Abstract: The objective of this study was to assess if high dietary zinc (Zn) fed to gestating sows modulates the microbiome of the sow and that of their offspring. Sows were fed 1 of 3 dietary treatments: 1) Control: a corn-soybean meal-based diet containing 125 ppm total supplemental zinc, 2) Breed-to-Farrow: as Control + 141 ppm supplemental Zn as ZnSO₄ fed from 5 days post-breeding to farrowing; and 3) Day 110-to-Farrow: as Control + 2,715 ppm supplemental Zn as ZnSO₄ starting on day 110 of gestation until farrowing. A subset of third parity sows (n = 30; 10 per treatment) were selected to assess the microbiome of colostrum, milk, and rectal and vaginal surfaces of sows. At farrowing, 4 pigs per litter (n = 120) were selected based on birthweight (BiW; 2 average BiW pigs and 2 pigs with BiW below the litter average) were selected to assess the piglet gut microbiome on the day of birth (day 0) and day 5 of age. 16S rRNA sequencing was implemented for colostrum and milk samples while all other sample types were sequenced using shotgun metagenomics to determine taxonomic and functional profiles. Measures of alpha and beta diversity were conducted along with determination of differentially abundant taxa and pathways in tandem with generalized linear mixed models. High dietary concentrations of Zn fed to gestating sows minimally affected their colostrum, milk, and vaginal microbiome. However, fecal samples of Breed-to-Farrow sows showed decreased abundance of potentially pathogenic bacteria such as Salmonella enterica and Shigella flexneri and greater abundance of bacteria typically involved in fiber fermentation compared to Control sows (Figure 1a). Piglets born to Day 110-to-Farrow sows also showed higher abundance of some taxa typically involved in fiber breakdown and short chain fatty acid (SCFA) generation on day 5 compared to Control pigs (Figure 1b). At day 0, Breed-to-Farrow piglets showed less abundance of methanogenic archaea and differential abundance of taxa with potentially pathogenic roles, compared to Control pigs (Figure 1c). Gene families and pathways playing roles in central metabolic functions (starch, pyruvate, sucrose, amino acid metabolism) were more abundant in Breed-to-Farrow piglets compared to pigs born to Control sows on day 0 and 5 of age. In conclusion, high Zn fed to gestating sows impacted the abundance of gut taxa with potential roles in SCFA-production and pathogenicity in both sow and piglet, despite overall minor effects. However, the physiological significance of these findings for the sow and piglet remains unclear.