Effect of slow-release copper alginate bead supplementation in swine feed on microbial fecal shedding and fecal microbiome.

2025, 20, 100803.
Background
Food safety starts with animal production at the farm level by ensuring that the appropriate pre-harvest interventions are implemented. The EPA recognizes copper as the first metallic antimicrobial, which has led to many studies on its antimicrobial properties.
Methods
Dehydrated alginate beads formulated with copper were synthesized and tested as a feed additive to influence the microbiota in finishing pigs and potentially use them as a pre-harvest intervention to reduce fecal pathogen shedding. The efficacy of the copper beads was tested in vitro in a quantitative assay with a Salmonella cocktail. In brief, Salmonella was exposed to copper alginate beads and enumerated on selective agar. The beads were tested in vivo by administering them to swine (N = 48) in a randomized block design with repeated measures in time. Fecal samples were collected and transported to the laboratory for microbial testing. Enterobacteriaceae (EB) and Lactic Acid Bacteria (LAB) were enumerated. Fecal samples were selected at random for microbiome analysis.
Results
In vitro, Salmonella was significantly (P < 0.05) reduced when in contact with the copper beads solution for up to six hours, with a 5.4 Log CFU/ml reduction over the first hour. Chemical analysis of the soak solutions demonstrated the beads delivered their copper payload gradually over the same period, and the bactericidal effect was observed. In vitro results showed that after treatment EB increased by 1.07 log. In vitro results showed that after treatment, EB increased by 1.07 Log. When beads were removed from the feed, EB and LAB concentrations returned to baseline, indicating copper beads led to measurable and significant changes in microbial loads. Fecal microbiome analysis demonstrated an increase in Firmicutes, Euryarchaeota, and Acidobacteriota at the phylum level. At the genus level, an increase in Methanosphaera and Pseudomonas was observed.
Conclusion
In the current study, slow-release dehydrated copper beads were formulated and seamlessly incorporated into feed, allowing copper to remain longer in the gastrointestinal tract of animals, reach deep into both the foregut and hindgut, and shift microbial populations. The technology delivers antimicrobial copper to the animal hindgut, and at the right concentration, copper was successfully delivered to the GI tract and alter the microbiota.