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Abstract

Influence of season and age on sexual maturation parameters of Texel, Suffolk and Ile-de-France rams: 1. Testicular size, semen quality and reproductive capacity.

Abstract

Scrotum diameter, quantity and quality of semen, and serving capacity of 6 Texel, 9 Suffolk and 9 Ile-de-France rams were compared at 2 and 3 years of age. Scrotal diameter increased rapidly during the 2nd year and slowly during the 3rd year, increasing in autumn and decreasing in winter and spring in both years (P<0.05). Scrotum diameter was greater in Ile-de-France than in Texel rams (P<0.05), with Suffolk rams intermediate. Volume and sperm concentration of the first ejaculate did not differ with age and breed. Ejaculate volume increased slightly in autumn and decreased in winter and spring in Texel and Suffolk but not in Ile-de-France rams. Sperm concentration did not differ with season. The percentage of dead and abnormal spermatozoa decreased (P<0.01) with age and was lower in autumn and increased in winter and spring during the 3rd year for Suffolk and Ile-de-France rams (P<0.05). Sperm motility varied independently of age and season. Semen quality (motility score and percentage of dead and abnormal spermatozoa) was higher in Ile-de-France and Suffolk than in Texel rams up to 27 months of age. Serving capacity increased (P<0.05) with ram's age and varied throughout the year, the lowest values being observed in spring and summer. Sperm production, evaluated by an exhaustion test at 3 years of age, was higher (P<0.05) in Ile-de-France than in the 2 other breeds around the spring equinox. In contrast, semen yield of Texel rams was the highest (P<0.05) at the autumn equinox and winter solstice. Frequent ejaculations lowered semen quantity, an effect that varied among breeds throughout the seasons. [For Pt. II see pp. 81-88 of the same number of the journal.]