Distribution of variance associated with measurement of post-thaw function in ram sperm.

Post-thaw characteristics of ram semen frozen as pellets were assessed using biochemically (amidase activity) or motility-based (Hamilton Thorn Motility Analyzer) techniques. The total variation associated with each semen characteristic measured was partitioned between rams, ejaculates within rams, pellets within ejaculates and within pellets. A variety of variance distributions were observed for the characteristics measured. Of the 18 post-thaw characteristics examined, 10 had higher than 50% of variance distributed between within-ejaculate components. This has important implications for the way in which such measurements may be used in post-thaw semen analysis.