FEEDS 



421 



HORMONES 



Recently there has been much interest in the use of synthetic sex 

 hormones in fattening poultry and beef cattle. Diethylstilbestrol 

 (page 323) has been used successfully for such purposes. Tablets 

 of the hormone implanted in the head of the animal or added to the 

 ration lead to increased gain in weight and increased feed efficiency. 

 Such implantation or addition to the ration must be controlled, or 

 undesirable side effects such as elevated tails, sagging loins, and mam- 

 mary gland development may occur. Implantation of diethylstilbes- 

 trol in the heads of cockerels several weeks before slaughter has a 

 feminizing effect and produces a fatter, tenderer carcass. Addition of 

 the hormone to the ration of poultry is not nearly as effective as with 

 beef cattle. Thyroprotein supplements have also produced added 

 gains in beef cattle. 



There is evidence that many plants contain compounds with es- 

 trogenic properties. A part of the beneficial effect of young pastures 

 on milk production may be due to such hormone-like chemicals. 

 Genistein, a 5,7,4^-trihydroxyisoflavone, has been isolated from sub- 

 terranean clover in quantities of 2 mg. of the hormone per 100 g. of 

 fresh clover. The activity per unit weight is very low compared with 

 that of estrone, but the high content in subterranean clover makes 



OH 



HO 



OCHc 



coumestrol 



it an important factor in sheep breeding in Australia. A similar 

 compound, biochanin A, is found in lower quantities in red clover. 



