Novel feed additive delivers antimicrobial copper and influences fecal microbiota in pigs

Dehydrated alginate beads formulated with copper were synthesized and tested as a feed additive to influencethe microbiota in finishingpigs and potentially use them as a preharvest intervention to reduce fecal pathogen shedding. The efficacyof the copper beads was tested in vitro and in vivo. In vitro, Salmonella was significantly(P < 0.05) reduced when in contact with the copper beads solution for up to 6 h, with a 5.4 log CFU/mL reduction over the firsthour. Chemical analysis of the soak solutions demonstrated the beads delivered their copper payload gradually over the same period the bactericidal effectwas observed. For the in vivo experiments, pigs (n = 48) supplemented with the copper beads experienced significantshifts in their microbiota. Enterobacteriaceae (EB) increased by 1.07 log CFU/g (P < 0.05), while lactic acid bacteria (LAB) decreased by 1.22 log CFU/g (P < 0.05) during the treatment period. When beads were removed from the feed, EB and LAB concentrations returned to baseline, indicating copper beads led to measurable and significantchanges in microbial loads. Fecal microbiome analysis conducted to explore additional changes by copper bead supplementation demonstrated that, at the phylum level, there was an increase in Firmicutes, Euryarchaeota, and Acidobacteriota, while at the genus level, an increase in Methanosphaera and Pseudomonas was observed. Measures of copper in swine feces showed values ∼20 times higher in the treatment group than in the control group during the treatment period, suggesting that dehydrated alginate copper beads were effectivein delivering antimicrobial copper to the animal hindgut.