[Promotion of fattening in young bulls following the administration of mestranol].

Oral administration of 5 mg mestranol daily for 100 days to 70 German Black Peid bulls improved weight gain in 72% of the animals. Average additional increment ranged from 2 to 17%. During the first weeks of administration there was a weak and transient protein-anabolic action and improvement in digestion of crude protein. Appetite was slightly stimulated. Consumption of food and energy per unit of weight gain was improved; better growth led to higher slaughter weight. Treatment had no effect on meat to bone ratio, degree of fulness of the gastointestinal tract, or meat quality. Skeletal mineralization was improved by 10-30%, and there was a noticeable anabolic effect on mineral metabolism. After longer administration an antigonadotropic action became evident. Some veterinary indications for use in fattening cattle were derived from these effects. Further pharmacological and clinical investigation of this and more active anabolics seemed to be required.