Effect of Repeated Freeze-Thaw Cycles on Survival of Bull Spermatozoa

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Abstract
The following assumption was evaluated: Immobilization is the sole deleterious consequence of freeze-thawing and its rate is controlled by simple probability relations. Observed percent motility of spermatozoa in the same sample population exposed to 5 repeated cycles of freeze-thawing was compared with predicted (calculated) values for each cycle based upon probability relations. Statistical analysis of results with 78 samples revealed that survival was not controlled by simple probability. Additional experiments confirmed the suggestion that some spermatozoa, although motile after freeze-thawing, are injured or weakened, as shown by their diminished resistance to storage as well as rapid cooling above the freezing temperature. Such weakening occurred during freeze-thawing and not as a result of post-thaw contact with an adversely altered extender.

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