Post-thaw motility, ATP content and cytochrome C oxidase activity of A.I. bull spermatozoa in relation to fertility.

Relationship between post-thaw sperm motility, ATP content, Cytochrome c oxidase (Cco) activity and fertility (56 days non-return) were determined in frozen-thawed semen. Semen was obtained from 47 A.I. bulls, and only ejaculates with a post-thaw sperm motility of greater than or equal to 50% were used. The post-thaw sperm motility was 52.7 +/- 6.9% (means +/- SD) at 30 min. The overall mean concentration of ATP was 18.7 +/- 5.6 nmol/spermatozoa x 10(8). Sperm motility, Cytochrome c oxidase activity and ATP content were found to be related to each other (r = 0.57-0.64; p less than or equal to 0.05-0.001). However, only ATP content showed a statistical significant but negative correlation (r = -0.24) with fertility. No correlation was found between post-thaw motility and fertility (56 days non-return within examined freezings). The results obtained raise doubts about the usefulness of sperm motility as an indicator of the fertilizing ability of frozen-thawed semen with a post-thaw motility of greater than or equal to 50%.