WOOL GROWTH IN SHEEP AS AFFECTED BY THE ADMINISTRATION OF CERTAIN SEX HORMONES

Three experiments were conducted to determine the effect of certain sex hormones on wool growth in sheep. The administration of estradiol intramuscularly caused a significant (P <.01) reduction in the average weight of clean wool and fibre length obtained from tattooed areas. In addition, this treatment reduced average thyroid weight, but increased pituitary and adrenal weights. It is suggested that the reduction in wool production resulted from a lowered thyroid activity and from adrenal cortical stimulation.The use of diethylstilbestrol orally produced the same general effects as estradiol but to a lesser degree.The administration of a single implant of diethylstilbestrol (12 mg.) to ewe lambs had no effect on wool growth. However, a second implant, administered 3 months after the first, resulted in a significant decrease in the average weight of clean wool from a measured area when compared to the controls.Testosterone significantly (P <.05) increased the weight of clean wool when the sheep were treated with relatively high doses (up to 175 mg.) during the first part of the experiment and lower doses (75 mg.) during the latter part. However, in another experiment where 125 mg. per head was used throughout the trial no response in wool growth was obtained. In the latter experiment there was some indication that thyroid activity was stimulated, suggesting that the testosterone dose was at the lower threshold level for wool growth.Progesterone given intramuscularly had no effect on wool growth in this study.