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.

A Phytoestrogen Diet Induces the Premature Anovulatory Syndrome in Lactationally Exposed Female Rats1

“…The normal response of these ewes to GnRH [13], combined with the anatomical evidence of hypothalamic damage [10], suggests a hypothalamic defect [13]. Moreover, female mating behavior is impaired, and malelike courting behavior can be induced following castration and testosterone treatment [14]. These symptoms, which develop in adult ewes following prolonged grazing on isoflavonoid-rich pasture, resemble the effects of steroidal estrogens and androgens on the perinatal differentiation of reproductive function in rodents [2].…”

Persistent infertility in ewes after prolonged exposure to oestradio-17

“…The cervical malfunction is associated with a reduced spinnbarkeit (capacity to be drawn into threads) in the cervical mucus (Adams, 1976) and a change in the histological structure so that the cervical archi¬ tecture and cells appear more like endometrium (Heydon & Adams, 1977). These changes occur as part of a general sexual transdifferentiation in affected ewes (Adams & Tang, 1986), and are accompanied by slight defeminization and masculinization of sexual behaviour (Adams, 1983) and an impairment of the sex-dependent mechanism controlling the preovulatory surge of LH (Adams Such sexual transdifferentiation is most unusual in adult mammals, and the question arises as to whether it is an aberrant response to oestrogenic isoflavones, or whether it can also be produced by a more physiological oestrogen such as oestradiol-17ß. In the present study, therefore, adult ewes were exposed to oestradiol-17ß for a prolonged period and examined for the functional abnormalities which have been reported in ewes with clover disease.…”