Sexual behaviour of ewes with clover disease treated repeatedly with oestradiol benzoate or testosterone propionate after ovariectomy.

Abstract

Ovariectomized ewes, 14 with permanent clover disease infertility (affected ewes) and 14 controls, were injected daily with 40 micrograms oestradiol benzoate for 12 days, and run with 2 rams fitted with marking crayons. The control ewes were mated sooner (P less than 0.05) but both groups became refractory at a similar rate. In a second experiment, 20 similar affected ewes and 19 controls were injected daily with 5 mg testosterone propionate for 31 days and observed daily for 50 min with rams. Affected ewes again were slower to show female behaviour (P less than 0.05) but faster (P less than 0.05) to show aggression against the rams and other ewes. Over the 31 days, the incidence of female sexual behaviour declined at a similar rate in affected and control ewes. When examined in individual pen tests with oestrous ewes on Day 28, affected ewes showed more male-like courting behaviour than did controls (P less than 0.05). The changes in behaviour are too slight to account for the infertility but they do support the hypothesis that phyto-oestrogens can act on the ewe by some of the pathways of sexual differentiation, even after puberty.