Feed is a recognized route for some swine disease to sneak into your operation. As viruses continue to persist in feed under standard storage conditions, the swine industry has adopted feed additives called mitigants to help reduce the viral load in feed. Another commonly used strategy is feedback, exposing replacement gilts and gestating sows to pathogens via oral ingestion of contaminated material.
Rachel Kontz, a veterinary medicine student at the University of Minnesota, wanted to better understand how these two common practices interact. She set out to evaluate the impact of feed mitigants on the efficacy of feedback at three distinct timepoints. Her goal? To determine if she could simulate pathogens expected to be encountered during various stages of production and help inform best practices for disease management and biosecurity.
“This study evaluated whether commercial feed mitigants impact the viability of pathogens used in oral feedback,” she said during the Allen D. Leman Swine Conference. “Feed samples were collected from two sow farms, each using a different mitigant.”
The samples were then inoculated with either an E. coli vaccine (Edema Vac F18) or a PRRS modified live virus vaccine (Ingelvac PRRS MLV) to simulate feedback conditions. Samples were tested at three time points: 30 minutes, 2 hours and 12 hours to simulate on-farm mixing intervals. At each of those time points, Kontz assessed pathogen viability using culture methods for E. coli and PCR for PRRSV RNA detection.
A Potential Conflict
All E. coli-treated samples showed strong bacterial growth at all time points, regardless of the mitigant or farm source. All PRRS-treated feed samples tested negative via PCR and virus isolation at all time points.
“The key finding was that feed mitigants did not affect E. coli viability, meaning bacterial feedback likely remains effective in the presence of mitigants,” she says. “However, the PRRS virus was eliminated at all time points, suggesting the mitigants may inactivate viral agents used in feedback.”
This highlights a potential conflict, Kontz says. While mitigants enhance biosecurity by reducing viral transmission risk, they may also undermine the intended immune response from feedback.
She believes this research provides critical insight for swine producers who use both mitigants and feedback as part of their herd health protocols.
“Understanding that mitigants may interfere with feedback can help producers make more informed decisions and work with veterinarians to adjust protocols,” Kontz says. “Ultimately, this can lead to more effective disease management strategies that balance biosecurity with herd health.”
She was one of seven finalists for the Morrison Swine Innovator Prize recognized during the Allen D. Leman Swine Conference. She presented her research findings during a session at the conference.
