The Formation of Antigonadotrophin in Sheep and Its Effect on the Endocrines and Reproductive System

Abstract

Eight female sheep were treated twice weekly with various doses of equine gonadotrophin injected either subcutaneously or intravenously. Antigonadotrophic activity appeared by the second week with injections of 200 IU, by the third week with 500 IU, and by the fifth week with the highest dose (1000 IU). In the last case, maximum activity was delayed until the 7th week. Route of injection did not influence rate of formation. When injections were discontinued, the antigonadotrophic potency of the serum was reduced after three weeks, but the levels again rose rapidly upon resumption of treatment, soon equaling or exceeding the former levels. Prolonged administration of gonadotrophin did not influence the weights of the pituitary gland, adrenal, thyroid, or ovaries. When large doses of equine gonadotrophin (500 or 1000 IU) were injected twice weekly, the ovaries remained acyclic and pituitary LH content was significantly reduced.

The effect of season on the ovulatory response of Merino ewes to serum from pregnant mares

“…If sheep are injected more than once with PMSG, the ovulatory response may decrease (Pigon, Clegg & Cole, 1960;Hulet & Foote, 1967;Clarke, 1973). It has been suggested that this is because follicular reserves are depleted (Edwards & Fowler, 1960) or antibodies or antigonadotrophic factors have been formed (Greenwald, 1963;Land & McLaren, 1967;Hulet & Foote, 1969).…”

Anti-PMSG antibody levels in sheep subjected annually to oestrus synchronisation

“…Studies on cattle (Willet et al, 1953;Christie et al, 1979;Alwan et al, 1988), and goats (Maurer et al, 1968;Gherardi and Martin, 1978;Armstrong et al, 1983;Remy et al, 1991;Baril et al, 1992b;Beckers et al, 1995) (Pignon et al, 1960;Jainudeen et al, 1966;Maurer et al, 1968;Alwan et al, 1988;Bavister et al, 1986;Remy et al, 1991;Baril et al, 1992b). Moreover, Beckers et al (1995) showed that goats treated with eCG, transmitted anti-eCG antibodies in their colostrum.…”