Changes in the Profiles of Serum Lh, Fsh and Testosterone, and in Mating Performance and Ejaculate Volume in the Ram during the Ovine Breeding Season 1 ,2,3

Changes in profiles of serum luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone and in mating performance and ejaculate volume have been determined in Finnish Landrace (F inn)and Managra Synthetic (Line-M) rams during the ovine breeding season. In early August, mid-September, early November and mid-December four rams of each breed were bled by venipuncture from the jugular vein at 20-min intervals for two 8-hr periods. Rams were bled while in the absence (control period) and presence (mating period) of ewes in estradiol-induced estrus. An ejaculate was also collected from either five or six of the rams during these months. Aliquots of serum were assayed for LH, FSH and testosterone by radioimmunoassay. Testosterone concentrations in seminal plasma were also determined. Episodic increases in serum levels of LH and testosterone were evident in all rams during each 8-hr period, while FSH fluctuated very little from baseline concentrations (usually