The safety of dimetridazole alone and in conjunction with oxytetracycline in Hereford crossbred steers.
Dimetridazole was given intraruminally alone, and in conjunction with oxytetracycline to healthy, 10-11 month-old Hereford cross-bred steers (n = 6). Intraruminal treatment with dimetridazole was given through a fistula at 75 mg kg-1 daily for 5 d, while the oxytetracycline was injected intramuscularly at 10 mg kg-1 on Days 1 and 3 of the dimetridazole treatment. The animals were observed at various intervals throughout the trial period for adverse reactions, including effects on ruminal activity and motility, changes in live-mass, venous acid-base balance, haematology and ruminal and serum ammonia concentrations. Dimetridazole, either when used alone or in conjunction with oxytetracycline, had a marked effect on ruminal function. Within 6 h of dosing, the ruminal pH fell to below 5, but then returned to pretreatment values over the next 24-48 h. This was followed by the eradication of the ruminal protozoal population in all animals tested and an increase in the methylene blue reduction time to more than 6 min. Ruminal motility remained unaffected throughout this period. During the week of treatment, the mean live-mass of the animals dropped by 20 +/- 9.9 kg in the dimetridazole treated group and by 13.3 +/- 2.8 kg in the animals treated with both dimetridazole and oxytetracycline. A mild to severe watery diarrhoea, which continued for 1 to 2 d, occurred in 4 animals after the first dimetridazole treatment. A compensated metabolic acidosis and an increase in haematocrit were observed. An initial transient rapid rise in rumen ammonia concentrations did not result in a concurrent rise in serum ammonia concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Pharmacology and Toxicology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, Republic of South Africa.
G E
GE
Swan
A
A
Shakespeare
M S
MS
Mülders
P P
PP
Minnaar
T W
TW
Naudé
H T
HT
Groeneveld
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D004131:Dimetridazole / Q000008:administration & dosage / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D008297:Male; D010118:Oxytetracycline / Q000008:administration & dosage; D014245:Trichomonas Infections / Q000188:drug therapy / Q000662:veterinary*
D004131:Dimetridazole; D010118:Oxytetracycline