2012 Annual Report 1a.Objectives (from AD-416): The ultimate objective of this research is to provide pork producers with practical treatment and withdrawal guidelines for the use of penicillin G procaine in sows. Specific objectives are to:. 1)provide the pork industry guidelines on appropriate patterns of intramuscular delivery of penicillin G procaine to sows;. 2)provide the pork industry with appropriate withdrawal periods for sows treated with penicillin G procaine under treatment conditions typically recommended by veterinarians; and. 3)to determine the incidence of "false-positives" returned by the "Charm-KIS" microbial inhibition test under controlled conditions. 1b.Approach (from AD-416): Heavy sows (>400 lb) will be treated with a 5x penicillin G procaine dose via intramuscular administration on 3 consecutive days. Three patterns of drug administration will be provided to three separate groups of sows: Treatment 1: A maximum injection volume of 10 mL will be administered to sows, but within day, multiple injections will be made into a single muscle group to deliver the total required drug volume (5 mL/100 lb BW); Treatment 2: A maximum injection volume of 10 mL will be administered, but within day, multiple injections will be made to separate muscle groups to deliver the total required drug volume (5 mL/100 lb BW); and Treatment 3: A maximum injection volume of 20 mL will be administered to sows, but within day, using multiple injections will be made to separate muscle groups to deliver the total required drug volume (5 mL/100 lb BW). Sets of 9 hogs each will be slaughtered at 5, 10, 15, 20, 25, 32, and 40 days after the last drug administration. The study will be replicated twice for a total of 126 treated sows. Kidney and will be analyzed using qualitative (microbial inhibition) and quantitative (LC-MSMS) methods approved by the FSIS. Residue depletion data will be plotted with time and withdrawal periods estimated using established methods. 3.Progress Report: A research project was initiated in which 160 heavy sows were purchased and housed at the North Dakota State University Animal Nutrition and Physiology Center. While at the center, animals were used in a cooperative research project between the ARS, NDSU, and the National Pork Board. Prior to the initiation of studies, a detailed study protocol was approved by the Institutional Animal Care and Use Committee. Experimental swine (n = 126) were treated intramuscularly with a 5x dose of penicillin G procaine on each of three consecutive days. Subsets of 42 sows were provided penicillin G procaine in three defined injection patterns (treatments) representing those commonly used in industry settings. Sows (n=6) from each treatment were each processed with withdrawal periods of 5, 10, 15, 20, 25, 32, and 39 days. At processing, edible tissues including skeletal muscle and kidney were collected for penicillin G analyses by LC-MS-MS; the same tissues were evaluated using the CHARM-KIS rapid screening kit. Animals were processed in a USDA-inspected facility using standard techniques. The live phase of the project has been completed. Analysis of tissues for penicillin residues is currently in progress at the USDA-ARS-Biosciences Research Laboratory.