USE OF ANTIBIOTICS, HORMONES, TRANQUILIZERS, AND OTHER 
CHEMICALS IN ANIMAL PRODUCTION 
N. R. Ellis, R. E. Davis, and C, A. Denton! 
The use of feed adjuncts or additives in the current sense of the term is a develop- 
ment of the past 20 years. The preceding 20 years witnessed the development of informa- 
tion on vitamins and ona number of mineral elements. Antibiotics, organic arsenicals, 
tranquilizers, and surfactants were unknown insofar as livestock feeding was concerned. 
Hormones were just on the horizon. 
The interest in hormones 20 years ago was largely from the standpoint of physio- 
logical function. Only a few investigators were studying the effects of hormone prepara- 
tions in livestock. Thyroid regulation appeared to be an attractive field. Among the 
studies in this area, that of Andrews and Bullard (1) appears significant to this review. In 
1940, they reported results of some studies on the effects of partial thyroidectomy on the 
fattening of steers. This represented an effort to alter the normal hormonal pattern in 
finishing animals for market. By circumstances or otherwise it paved the way for de- 
velopments in direct feeding of thyroidal compounds rather than surgical treatment. 
The World War II years witnessed initial research on feeding compounds to various 
classes of livestock having thyrogenic properties. Control of thyroid status seemed to 
offer great possibilities in animal production through the use of products that produced 
hyperthyroidism on the one hand and hypothyroidism on the other. 
During the 1945-1950 period numerous research studies were reported on the use of 
synthetic goitrogens that produced varying degrees of hypothyroidism. The more common 
compounds were the several forms of thiourea and thiouracil. Concurrently and extending 
up to 1955, there was much interest in hyperthyroid-producing materials --principally' 
thyroxine. Much work went into the development ofa product variously known as iodinated 
casein, thyroprotein, and other names carried thyroxine activity. Synthetic thyroxine also 
made its appearance. Much of the interest was in the feeding of dairy cows. Recently, 
there has been reactivation of research in swine. 
During the 1943-1945 period a number of research reports appeared on the use of 
estrogens in poultry fattening, followed by an apparent lull lasting until about 1950, even 
though a new drug application for the use of stilbestrol implants became effective in 1947. 
Extensive research with stilbestrol and other sex hormones began about 1950 on 
cattle, sheep, and swine, and was resumed on poultry in 1951. Since that date there has 
been widespread activity in this area. In 1954, the oral administration of stilbestrol in 
beef cattle came into general use through the granting-of a new drug application. The 
permit for marketing of stilbestrol pellets for implantations in the ears of beef cattle 
became effective in 1955, In the case of sheep, application was allowed for oral admin- 
istration in 1957, and for pellet implantation in the ear in 1959. Various groups of hor- 
mone products that have been studied are listed below: 
Some Hormones Tested in Feeding Experiments 
Thyroidal Female sex 
Thyroxine Estradiol 
Iodinated protein Dienestrol 
Triiodothy ronine Diethylstilbestrol 
Hexestrol 
Goitrogens Progesterone 
Thiouracil (various forms) 
Thiourea (various forms) Male sex 
l-methyl, 2-mercaptoimidazole Testosterone 
Methyl androstenediol 
* Associate Director, Animal Husbandry Research Division, Nutritionist and Leader, Beef Cattle Nutrition Investigations, and 
Chemist (Biochemist) and Leader, Poultry Nutrition Investigations, respectively, Animal Husbandry Research Division, Agricultural 
Research Service, U. S, Department of Agriculture, 
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