Tissue disposition and depletion of penicillin G after oral administration with milk in unweaned dairy calves.
OBJECTIVE
To determine tissue depletion of penicillin G in calves after oral ingestion with milk replacer and estimate a withdrawal period.


METHODS
Longitudinal controlled trial.


METHODS
26 Holstein calves.


METHODS
Once daily, 24 calves were fed milk replacer containing procaine penicillin G (0.68 mg/kg [0.31 mg/lb] of body weight); 2 calves served as controls. After 1 feeding, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after feeding. After 14 days, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after the final feeding. Concentrations of penicillin G were determined in tissues, blood, and urine by use of high-performance liquid chromatography.


RESULTS
Penicillin G was not detected in muscle samples of treated calves. The highest concentrations of penicillin G in plasma, kidney, and liver were 13 ng/ml, 92 ng/g, and 142 ng/g, respectively. Thirteen carcasses had violative drug residues; 12 had violative residues in the liver only, and 1 had violative residues in the liver and kidney. A 21-hour withdrawal period was estimated.


CONCLUSIONS
Liver had the highest concentration of penicillin G and was most likely to have violative residues. Feeding calves milk containing penicillin G has the potential to cause violative drug residues in tissues. It is recommended to observe an appropriate withdrawal time prior to slaughter if calves are fed milk from cows treated with penicillin G.
Musser
J M
JM
College of Veterinary Medicine, Department of Farm Animal Health and Resource Management, North Carolina State University, Raleigh 27606, USA.
Anderson
K L
KL
Boison
J O
JO
D000284:Administration, Oral; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D004350:Drug Residues / Q000032:analysis / Q000493:pharmacokinetics*; D006207:Half-Life; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008137:Longitudinal Studies; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism; D010400:Penicillin G / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D010406:Penicillins / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D014018:Tissue Distribution
D010406:Penicillins; D010400:Penicillin G