THE PROFILE OF FOLLICLE-STIMULATING HORMONE SECRETION IN THE RAM

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Abstract
Blood serum levels of follicle-stimulating hormone (FSH) were observed in rams at various times throughout the year, during a period of intense mating and following treatment with gonadotropin-releasing hormone (Gn–RH). The level of FSH in peripheral blood of two mature rams sampled at 20-min intervals for 24 h in August and January was relatively stable compared to the level of luteinizing hormone (LH). The small elevations in FSH (usually < 50% of baseline values) which were noted did not coincide with or closely follow LH releases. FSH levels were significantly (P < 0.01) lower in both animals in January than in August. These two rams were allowed to mate estrual ewes for a 24-h period in January during which time blood samples were collected as in the non-mating period. Mating activity during the first 12 h was associated with larger elevations and a significantly (P < 0.01) higher mean level of FSH in both animals, in contrast to the comparable non-mating period. Six ram lambs sampled at 2- to 3-wk intervals from May through December exhibited significantly (P < 0.05) higher FSH levels in July and August compared to the other months. No appreciable change in FSH was noted in two additional mature rams when treated with synthetic Gn–RH (10 μg given i.v.) six times over a 9-h period, although marked increases in LH and testosterone occurred.

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