Use of a new and rapid milk progesterone assay to monitor reproductive activity in the cow

A new and rapid enzyme-amplified immunoassay (AELIA) has been developed for the measurement of progesterone in milk. The AELIA system is a non-isotopic method that gives results within 35 minutes. Milk progesterone concentrations measured in 10 cows sampled daily at various stages of the reproductive cycle were very similar to those recorded by a validated radioimmunoassay. The results show that the speed and sensitivity of the AELIA system would make it possible to diagnose pregnancy rapidly at about 24 days after insemination, to predict the onset of behavioural oestrus from decreasing progesterone values during the third week after a preceding oestrus, and to obtain a daily record of milk progesterone levels in animals treated for infertility of ovarian origin.     

Intramammary antibiotic preparations and their withholding times

The test for antibiotic residues in milk carried out by the Milk Marketing Board (MMB) of England and Wales was increased in sensitivity from 0.02 iu/ml penicillin or equivalent to 0.01 iu/ml on January 1, 1986. The Veterinary Products Committee (VPC) has just completed a review of those intra-mammary antibiotic preparations which had licences of right. When assessing data for product licences the VPC decided that the concentration of antibiotic residues in milk should not exceed the concentrations listed in the 1969 Report of the Joint FAO/WHO Expert Committee on Food Additives. In this publication the level of 0.006 ppm for penicillin corresponds to 0.01 iu/ml which is the level that the MMB will also be using.     

Reversal of pentobarbital anesthesia with 4-aminopyridine and yohimbine in cats pretreated with acepromazine and xylazine

In 2 separate experiments, groups of atropinized cats (6 cats/group) were given acepromazine (0.25 mg/kg of body weight) or xylazine (2.2 mg/kg) IM and anesthetized with pentobarbital. The mean dose of pentobarbital was decreased approximately 36% by acepromazine, and approximately 80% by xylazine, compared with published doses. Anesthetized cats were given IV saline solution (control groups) or were given the antagonists 4-aminopyridine (4-AP; 0.5 mg/kg), yohimbine (0.4 mg/kg), or 4-AP + yohimbine (0.5 mg/kg and 0.4 mg/kg, respectively). In acepromazine-treated cats, 4-AP + yohimbine was the most effective antagonist; arousal and walking occurred in an average of 10.4 minutes and 91.7 minutes, respectively. Yohimbine enhanced the antagonistic effects of 4-AP. In xylazine-treated cats, yohimbine was an effective antagonist; arousal and walking occurred in an average of 2.8 minutes and 12.8 minutes, respectively. Yohimbine did not enhance the antagonistic effects of 4-AP. Mean respiratory rates were decreased by acepromazine, but were increased by xylazine. Thus, respiratory rate depression by pentobarbital was not as marked with xylazine as it was with acepromazine. Changes in mean heart rate were not remarkable with either sedative, and cardiac irregularities were not palpated or auscultated. In healthy cats, the duration of pentobarbital anesthesia can be controlled by 4-AP + yohimbine (acepromazine-pretreated cats) or by yohimbine alone (xylazine-pretreated cats).     

Comparative pharmacokinetics of yohimbine in steers, horses and dogs.

In steers, horses and dogs, the comparative pharmacokinetics of yohimbine were determined using model-independent analysis. The intravenous dose of yohimbine was 0.25 mg/kg of body weight in steers, 0.075 or 0.15 mg/kg in horses, and 0.4 mg/kg in dogs. The mean residence time (+/- SD) of yohimbine was 86.7 +/- 46.2 min in steers, 106.2 +/- 72.1 to 118.7 +/- 35.0 min in horses, and 163.6 +/- 49.7 min in dogs. The mean apparent volume of distribution of yohimbine at steady state was 4.9 +/- 1.4 L/kg for steers, 2.7 +/- 1.0 to 4.6 +/- 1.9 L/kg for horses, and 4.5 +/- 1.8 L/kg for dogs. The total body clearance of yohimbine was 69.6 +/- 35.1 mL/min/kg for steers, 34.0 +/- 19.4 to 39.6 +/- 16.6 mL/min/kg for horses, and 29.6 +/- 14.7 mL/min/kg for dogs. Between-species comparisons indicated that the mean area under the serum concentration versus time curve was significantly greater (P less than 0.05) in dogs than in horses. There were no significant differences (P greater than 0.05) between the means for the apparent volume of distribution, clearance, mean residence time, terminal rate constant, and area under the curve between horses given the two doses of yohimbine. The harmonic mean effective half-life (+/- pseudo standard deviation) of yohimbine was 46.7 +/- 24.4 min in steers, 52.8 +/- 27.8 to 76.1 +/- 23.1 min in horses, and 104.1 +/- 32.1 min in dogs. The data may explain why steers, horses, and dogs given certain sedatives and anesthetics do not relapse when aroused by an intravenous injection of yohimbine hydrochloride.     

Brodifacoum poisoning in a dog

A case of brodifacoum poisoning is described in a six-year-old male Kelpie cross working dog. The clinical features were severe exercise intolerance, haemorrhage from the oral and nasal cavities, dyspnoea and pale mucous membranes. Diagnosis was confirmed by demonstrating an abnormally long whole blood clotting time. The dog was treated successfully by administering 1 litre of whole blood intravenously, intramuscular vitamin K1 and a three week course of oral vitamin K3. Experience at the Massey University Small Animal Clinic and Hospital has indicated that poisoning of dogs with the newer long acting anticoagulant rodenticides is becoming more common.