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Seasonal Trends of Sperm Cell Types in Sheep^*

University of Minnesota

Abstract

The quality of ram spermatozoa changes markedly at different times of the year. The study of these seasonal trends is important to discover "normal" breed and individual variations. These studies are also important to determine the ability of rams to recover, before the breeding season, from lowered seminal quality due to summer environment.

McKensie and Berliner (1937) demonstrated that seasonal variations in both quantitative and qualitative seminal characteristics existed not only among rams but also between males of the Hampshire and Shropshire breeds. Their study, which was conducted for a period of one year, indicated that the seminal quality of the latter breed was reduced more during the summer months and remained at a lower level especially during the early portion of the breeding season. This slower recovery during the early autumn is undesirable in any ram because it indicates a lowered fertility and thereby a more prolonged lambing season.

Cytological studies were made on the semen of 12 purebred Shropshire rams. The project was started when the lambs were about ten months old (January 1939) and continued for one year.

^* Paper No. 1857, Scientific Journal Series of the Minnesota Agricultural Experiment Station. Contribution from the Animal Genetics Section, Division of Animal and Poultry Husbandry.