REDR1998 Reproduction in Domestic Ruminants IV Male Function and Fertility (4 abstracts)
Sexual behaviour of rams: male orientation and its endocrine correlates
JA Resko 1 , A Perkins 2 , CE Roselli 1 , JN Stellflug 3 & FK Stormshak 4
1Department of Physiology and Pharmacology, School of Medicine, Oregon Health Sciences University, Portland, OR 97201–3098, USA; 2Department of Psychology, Carroll College, Helena, MAO 59625, USA; 3US Sheep Experimentation Station, Dubois, ID 83425, USA; and 4Department of Animal Sciences, Oregon State University, Corvallis, OR 97331–6702, USA
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 oestrone, reduced capacity to produce testosterone in vitro, and reduced capacity to aromatize androgens in the preoptic–anterior hypothalamus of the brain. Our observation that aromatase activity is significantly lower in the preoptic–anterior hypothalamic area of male-oriented rams than in female-oriented rams may indicate an important neurochemical link to sexual behaviour that should be investigated. The defect in steroid hormone production by the adult testes of the male-oriented ram may represent a defect that can be traced to the fetal testes. If this contention is correct, partner preference behaviour of rams may also be traceable to fetal development and represent a phenomenon of sexual differentiation.
© 1999 Journals of Reproduction and Fertility Ltd
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