Date Full Report Received08/13/2013
Date Abstract Report Received08/13/2013
InvestigationInstitution: ARS, Biosciences Research Laboratory, USDA
Primary Investigator: David Newman, David Smith, Sara Lupton, Weilin Shelver
Funded ByNational Pork Board
A total of 126 heavy sows were treated with a 5x dose of penicillin G procaine via intramuscular (IM) administration for 3 consecutive days using 3 injection patterns. Sets of 18 animals (6 per injection pattern) were slaughtered at 5, 10, 15, 20, 25, 32 and 39 days and penicillin residues were measured in skeletal muscle and kidney samples. Residues in skeletal muscle depleted very rapidly and were not quantifiable by 15 days of withdrawal. The FARAD recommended 15-day withdrawal period is sufficient to ensure that skeletal muscle residues deplete to safe levels. Depletion of residues in kidney was much slower than in skeletal muscle. An estimated withdrawal period of 47 days would be required to ensure that residues in 99% of animals would be depleted below 50 ppb, with 95% confidence. Because this withdrawal period is prohibitively long for most commercial sow operations, it is recommended that sows treated IM with extra label doses of penicillin G procaine be slaughtered with a 15-d withdrawal period, with edible offal (kidney, liver) being discarded at the slaughter plant. In a second portion of the study, a commercially available rapid screening assay (Charm-KIS) was used to accurately predict the presence of violative penicillin-G kidney residues in kidneys. When used with urine, there was a very high correlation between positive urine results and penicillin-G positive kidney samples. Thus, the Charm-KIS assay could be employed by commercial sow producers to screen urine of treated animals for the presence of penicillin G residues in kidneys.