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 (5), ejaculates within rams (5), pellets within ejaculates (5) and within pellets (2). A variety of variance distributions were observed for the characteristics measured. Of the 18 post-thaw characteristics examined, 10 had > 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.