Rodenticide Ingestion in Swine: A Project to Assist Veterinarians with Detection and Establishing Withdrawal Times

Project 11-219 - Researcher: Ron Johnson

Rodenticides are commonly used in pig barns to control the number of mice and rats which can carry and spread disease or chew on wires causing issues with electrical systems. However the placement of rodenticides or the lack of use of a bait station can occasionally lead to accidental ingestion by pigs.  Researchers at the University of Guelph conducted a study feeding low (0.05 mg/kg) and high doses (0.5 mg/kg) of bromadiolone, a common rodenticide, to 40 market weight hogs to determine an appropriate withdrawal time and to create an easy residue test.  Their results showed that both blood and fecal samples can be used to detect bromadiolone, regardless of the amount consumed, however these tests are only effective for the first several days after ingestion. One week after eating the rodenticide, the residue can no longer be consistently detected in blood or feces, however it can still be detected in tissue. Tissue residues were found in the liver in all pigs (for 6 weeks post ingestion in HD pigs and 3 weeks in LD pigs).  In pigs that received the high dose, residues were also found in muscle and fat for weeks after ingestion of the rodenticide.  Based on liver levels and the observed rate of breakdown by the body, the appropriate withdrawal time for pigs who ingested low doses was determined to be 83 weeks, while the withdrawal time required for high dose pigs was 176 weeks. Based on these results, pigs that are suspected of ingesting rodenticide should never be marketed, as the time required for the rodenticide to clear from tissues is impractically long. 
 

Additional Resources:
Journal of Swine Health and Production-Nov/Dec 2015 issue 
Centralia Swine Research Update Jan 2014