Treatment of ewes at different stages of pregnancy with epidermal growth factor: effects on wool growth and plasma concentrations of growth hormone, prolactin, placental lactogen and thyroxine and on foetal development.

Pregnant ewes at 57, 75 and greater than or equal to 101 days of gestation were infused with approximately 3 mg of epidermal growth factor (EGF) for a period of 24-28 h. The strength of attachment of the wool fibres to the skin became progressively reduced during the week following treatment. After 3 weeks, the mean forces required to pluck staples had declined to between 10 and 30% of the pre-infusion measurements and the fleeces were able to be removed easily by hand. Increases in growth hormone and placental lactogen occurred in plasma of ewes during EGF treatment. Prolactin was not affected by EGF but circulating levels of thyroxine declined. The concentrations of these hormones returned to approximate pretreatment values within 24 h of the end of infusion. EGF treatment at the dose levels used did not appear to significantly affect the development or viability of the foetus.