Growth and Other Physiological Responses to Diethylstilbestrol in Diet of Rats and Guinea Pigs

Recent studies have shown that the inclusion of diethylstilbestrol (stilbestrol) in rations of fattening beef cattle (1) and lambs (2) results in stimulation of liveweight gains and improvement of overall feed utilization in these species of animals. The physiological explanations for this action of stilbestrol are not apparent at this time since no such stimulation from stilbestrol has been noted in other species of animals. In studying the mode of action of stilbestrol in fattening beef cattle and lambs, it seemed desirable to first study the growth responses of certain laboratory animals (rats and guinea pigs) to see if they might be used as pilot animals in making detailed physiological measurements which might later be applied to cattle and sheep physiology. Previous work with rats has shown a growth inhibition with estrogens (3, 4) : however, the levels administered have been relatively high