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Effect of Chlorpromazine on the Performance of Lactating Dairy Cows

Departments of Dairying and Biochemistry Oklahoma State University, Stillwater

ABSTRACT

Studies were conducted to determine the oral dosage of chlorpromazine required to produce tranquilization in lactating Holstein cows and to evaluate the effects of feeding low levels of the tranquilizer on milk production during a 24-wk. period.

In a series of trials involving six cows, no tranquilization was observed when as much as 5 g. of chlorpromazine per day was divided into two equal portions and fed with the grain ration at the morning and evening feedings. On the other hand, two cows showed a marked degree of tranquilization after receiving single doses of 4.5 and 9.0 g. of the tranquilizer, respectively. Thus, approximately 5 mg. of chlorpromazine per pound of body weight was effective in producing tranquilization in lactating dairy cows. No chlorpromazine was detected in the milk from the cows at any level of administration.

Twenty-four additional cows were used to evaluate the effects of feeding three different levels of chlorpromazine, i.e., 0, 250, and 500 mg. per day, on milk production under different environmental conditions. No appreciable differences were observed among treatment groups with respect to the production of 4% fat-corrected milk or body weight changes during the 24 wk. of the experiment.