FERTILITY IN THE EWE AFTER ARTIFICIAL-INSEMINATION WITH FRESH AND FROZEN-SEMEN AT THE INDUCED ESTRUS, AND INFLUENCE OF THE PHOTOPERIOD ON THE SEMEN QUALITY OF THE RAM

The effect was studied of photoperiod on semen quality of five adult Ile-de-France rams reared for a period of 1 year in a pen exposed to an artificial regime which reproduced the natural variations of daylength. Light induced large fluctuations in both cell morphology and in the fertilizing power of ejucalates. In spring, when semen quality is generally lower, it is possible to discard the poor ejaculates by checking the percentage of abnormal spermatozoa. This offers an additional argument for using artificial insemination, already known for its role in selection programmes, for the breeding of ewes treated by synthetic progestogens, and nowadays as a solution to sanitary problems. In France A.I. is used only after heat synchronization (about 150,000 ewes inseminated in 1977). Sperm is preserved mainly in a liquid state (2 × 109 spz/ml) and stored up to 10 h at +15°C in a solution of skim milk. Females are inseminated, regardless of the season: • - either once with 0.5 × 109 spz, 55 ± 1 h after removal in the dry ewe, 52 ± 1 h in the ewe-lamb, • - or twice (2 × 0.5 × 109 spz) in the lactating ewe, 50 and 60 h after sponge removal. When sperm is frozen in straws, the total amount of spermatozoa per ewe is 800 × 106. Adult females are inseminated only once 55 ± 1 h h after sponge withdrawal. Lambing rates are lower than that reached with fresh semen. They also depend upon the season of collection of the ejaculates. They are the highest during the breeding season (60.9%). © 1979.