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Further Studies on the Anabolic Effect of Stilbestrol in Cattle as Indicated by Carcass Composition

University of California

Abstract

During 1954 and 1955, three trials were carried out to determine the effect of stilbestrol on fat and protein deposition in the carcass. In trial 1, 16 two-year-old Hereford steers were divided into two equal groups. Group 1 served as a control group, group 2 was implanted in the ear with five 12 mg. pellets of stilbestrol. The animals were maintained on a fattening ration for 104 days, at which time they were slaughtered. Trial 2 was a replication of trial 1 except the feeding period extended for 185 days. In trial 3, 28 yearling heifers were divided into four groups as follows: Group I, spayed untreated; group II, spayed implanted with 60 mg. of stilbestrol in the year; group III, intact untreated; group IV, intact implanted with 60 mg. of stilbestrol in the ear. These animals were maintained on a fattening ration for 217 days before being slaughtered. Carcass cutout values, analysis of the percentage of separable fat, lean and bone of the 12th rib cut, analysis of blood constituents and histological studies of the seminal vesicles were made on appropriate animals. The data indicate that stilbestrol treatment resulted in a decreased fat deposition and an increased protein anabolism.

Treatment did not affect the percentage of bone nor the percentage of moisture in the steers, but caused a significant increase in moisture percentage in the heifers. Levels of plasma glucose and non-protein nitrogen, serum protein-bound iodine, potassium and sodium were unaffected by stilbestrol. There was a significant increase in the cross-sectional area of the eye muscle in all trials and an enlargement of the kidney of treated steers in trial 1. The average daily gain was increased as a result of stilbestrol treatment. Carcass grades were in some cases lowered and, in heifers but not in steers, dressing percentage was also reduced as a result of treatment.

Spaying had no effect on carcass grades, dressing percentage, average daily gains, or carcass constituents.

Histological studies of the seminal vesicles indicate a stimulated epithelium as well as an increased development of fibrous tissue.

¹ Department of Animal Husbandry, Davis.