Analysis of procaine penicillin G and ampicillin trihydrate residue depletion profiles in tissues and alternative matrices of cull sows

Abstract

This project determined the tissue, plasma, and urine residue depletion of procaine penicillin G in cull sows at label and extra-label doses, with corresponding calculation of withdrawal times. We also examined the utility of urine, plasma, and environmental samples as matrices for residue analysis, the potential for environmental residue contamination, and the performance of rapid tests kits KIS™, Charm MRL™, and Snap™ test in detecting residues. Forty-seven sows were assigned to a treatment group receiving 3,000 IU/lb IM SID procaine penicillin G (n=15), 15,000 IU/lb IM SID procaine penicillin G (n=16), or a negative control group receiving sterile saline injections (n=16). Sows were sampled at 1, 6, 14, and 28 days post-treatment. With a 25 ppb action level, kidney withdrawal time for extra label dosing at 15,000 IU/lb was determined to be 30 days. Injection site withdrawal time was estimated to be 37 days. Urine and plasma could both serve as representative matrices for ante-mortem residue testing. Snap™ and Charm MRL™ test kits on urine returned similar results to LC-MS/MS testing, making them good ante mortem screening tests. Environmental samples are not a good tool for residue detection and there is no evidence to support the environmental transfer of penicillin G from treated to untreated sows.