Combination of an Antibiotic and a Female Hormone for Fattening Steers

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Abstract
The feeding of 12 mg. of hexestrol per animal daily to two-year-old fattening steers in drylot resulted in a 24% increase in growth rate (2.03 vs. 2.50 lb. per day). When hexestrol and chlortetracycline (Aureomycin) were fed in combination, the growth stimulatory effect was almost exactly equal to the sum of effects of the two when fed separately, indicating the growth stimulatory effects of these two substances are exerted independently and are additive. Efficiency of feed conversion was improved when either the hormone or antibiotic was fed alone, but the efficiency of conversion was increased when the two were fed together by an amount that is 1.6 times as great as the sum of the figures for improvement brought about by feeding either alone. When both shrink-in-transit and dressing percent were calculated, cattle fed hexestrol suffered approximately 1% greater marketing and slaughter loss than cattle fed the antibiotic alone, than cattle fed both the antibiotic and the hormone, and than cattle fed neither antibiotic nor hormone. There was no apparent variation in carcass grades among the four lots of cattle. Chemical analysis of the meat from the twelfth rib showed the cattle fed the female hormone alone or in combination with the antibiotic contained less fat and more protein and water than meat from the animals fed antibiotic alone or else neither the hormone nor the antibiotic. Copyright © . .