Effect of stress during shearing on the LH response to GnRH in anoestrous ewes

Abstract

There is considerable evidence that stress causes an increase in plasma cortisol concentrations in sheep (Stephens, 1980). Stress had deleterious effects on female reproductive efficiency (Christian, Lloyd & Davies, 1965) possibly, in part, by suppression of gonadotrophin release by increased pituitaryadrenal activity (Wagner & Li, 1982; Moberg, 1984). Previous experiments from our laboratory (Dobson, Essawy & Alam, 1988) have shown that administration of synthetic adrenocorticotrophin hormone (ACTH 1–24) results both in increased cortisol release and suppression of the luteinizing hormone (LH) response to gonadotrophin releasing hormone (GnRH). The purpose of the present experiment was to investigate whether LH release is suppressed in ewes subjected to an environmental stressor.