The Effect of Progesterone-Estradiol Implants and Stilbestrol Feeding on Feed Lot Performance and Carcass Characteristics of Steers6

Abstract

Rate of gain, efficiency of feed conversion, physiological effects and certain carcass measures are reported for three lots of steers treated as follows: Lot I, control; Lot II, fed diethylstilbestrol (10 mg. per head daily); Lot III, implanted with combination progesterone-estradiol pellets (1.5 gin. progesterone and 50 mg. estradiol). Implanted steers had a significantly greater daily rate of gain than either stilbestrol-fed cattle or controls. Stilbestrol-fed steers had a significantly higher daily rate of gain than the controls. Average daily gains were 2.30, 2.64, and 3.03 lb., respectively, for the control, stilbestrol-fed and implanted steers. Implanted cattle ate an average of 16.0 lb. of corn per day, stilbestrol-fed steers 15.3 lb. and control steers 14.8 lb., indicating an increased appetite from hormone stimulation. There were no significant differences in dressing percentage, cooler shrink, heart, liver, spleen or hide. There were no significant differences in carcass grade. As estimated by the 9-10-11 rib cut (Hankins, 1946), carcasses from implanted steers had a significantly greater proportion of separable lean, and significantly lower proportion of separable fat than the carcasses for either stilbestrol-fed or control groups. Moisture of external fat, internal fat, Longissimus dorsi, and combined separable fat and lean was not significantly different between groups. No significant differences were found in percentage of ether extract of Longissimus dorsi, or of combined separable fat and lean. There was no difference in cooking shrink or in Warner-Bratzler shear readings. Adrenal glands appeared normal in all groups. Hormone treatment either by implantation or feeding resulted in an increased diameter of the prostatic portion of the urogenital tract and an increase in size of the bulbourethral glands and seminal vesicles, indicating physiological activity due to both hormone treatments. There was some evidence of secretory activity in the prostrate and bulbourethral glands of treated steers. There was no evidence of desquamation or keratinization of epithelium and no evidence of carcinogenesis in any tissues examined.