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Reproduction in Domestic Ruminants IV

Reproduction in Domestic Ruminants IV

Male Function and Fertility

bp0004rdr18 | Male Function and Fertility | REDR1998

Regulation of gonadotrophin-releasing hormone secretion by testosterone in male sheep

Hileman SM , Jackson GL

In males, including the ram, testosterone, acting via its primary metabolites oestradiol and dihydrotestosterone (DHT), suppresses circulating LH concentrations. This effect is due primarily, although not totally, to decreased frequency of gonadotrophin-releasing hormone (GnRH) pulses. The arcuate–ventromedial region (ARC–VMR) of the mediobasal hypothalamus and possibly the medial preoptic area (mPOA) are sites at which oestradiol acts to suppress GnRH, but the site ...

bp0004rdr19 | Male Function and Fertility | REDR1998

Role of male–female interaction in regulating reproduction in sheep and goats

Walkden-Brown SW , Martin GB , Restall BJ

The induction of synchronous ovulatory activity in anovulatory sheep and goats after the introduction of males, the 'male effect', has probably been used to advantage since these species were domesticated and the underlying physiological and behavioural mechanisms have been progressively elucidated over the past 50 years. Less well understood is the analogous effect of oestrous females on males. This review examines the nature and importance of these male–female i...

bp0004rdr20 | Male Function and Fertility | REDR1998

Sexual behaviour of rams: male orientation and its endocrine correlates

Resko JA , Perkins A , Roselli CE , Stellflug JN , Stormshak FK

The components of heterosexual behaviour in rams are reviewed as a basis for understanding partner preference behaviour. A small percentage of rams will not mate with oestrous females and if given a choice will display courtship behaviour towards another ram in preference to a female. Some of the endocrine profiles of these male-oriented rams differ from those of heterosexual controls. These differences include reduced serum concentrations of testosterone, oestradiol and oestr...

bp0004rdr21 | Male Function and Fertility | REDR1998

The functional integrity and fate of cryopreserved ram spermatozoa in the female tract

Gillan L , Maxwell WMC

Cryopreservation advances capacitation-like changes in ram spermatozoa. These changes are reflected in an increased fertilizing ability compared with fresh spermatozoa, followed by an accelerated decline in fertilizing ability after incubation in vitro or in vivo. Furthermore, frozen–thawed spermatozoa are released earlier than fresh spermatozoa after binding to oviduct cells in vitro, confirming their physiological readiness to participate in f...