Oxytetracycline residues in milk after intrauterine treatment of cows with retained fetal membranes.
OBJECTIVE
To establish the maximum concentration and duration of oxytetracycline residues in milk from cows with retained fetal membranes given the antimicrobial via intrauterine infusion, and to investigate whether the number of infusions or the presence of fever (> 39.7 C) affected the duration of residues.


METHODS
Prospective study.


METHODS
54 Holstein cows with retained fetal membranes on a single 1,400-cow commercial dairy.


METHODS
Cows were treated once a day with 5 g of oxytetracycline (50 ml of 100 mg/ml solution in a povidone base) by intrauterine infusion for at least 2 days, or until the membranes were expelled. Cows that became febrile (rectal temperature > or = 39.7 C) were also given 20,000 IU of procaine penicillin G/kg of body weight, i.m., for 2 to 4 days. Milk samples were collected at 24-hour intervals during treatment. and at 12-hour intervals after the last treatment. All samples were frozen and submitted every 2 weeks for high performance liquid chromatography analysis for oxytetracycline.


RESULTS
Oxytetracycline was detected in milk of all cows during treatment, at a maximum concentration ranging from 47.2 to 1,804.6 micrograms/kg (mean, 316.9 micrograms/kg). Duration of oxytetracycline residues after the last infusion ranged from 0 to 144 hours (mean, 52.3 hours). Neither the number of infusions received, nor development of rectal temperature > 39.7 C, affected the maximum concentration or the duration of oxytetracycline residues in milk.


CONCLUSIONS
Milk obtained from cows that had been treated for retained fetal membranes by intrauterine infusion of oxytetracycline should be discarded to avoid illegal residues.
Dinsmore
R P
RP
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins 80523, USA.
Stevens
R D
RD
Cattell
M B
MB
Salman
M D
MD
Sundlof
S F
SF
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D004350:Drug Residues / Q000493:pharmacokinetics*; D005260:Female; D007263:Infusions, Parenteral / Q000662:veterinary; D008892:Milk / Q000378:metabolism*; D010118:Oxytetracycline / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D018457:Placenta, Retained / Q000188:drug therapy / Q000662:veterinary*; D011247:Pregnancy; D011446:Prospective Studies; D014599:Uterus
D000900:Anti-Bacterial Agents; D010118:Oxytetracycline