Deleterious effect of seminal plasma in the cryo‐preservation of bovine spermatozoa

The effect of seminal plasma on spermatozoa was studied during freezing in a buffered diluent. The effect was assessed after thawing, both by visual assessment of motility and by colorimetric assay of aromatic L‐amino acid oxidase activity. The presence of seminal plasma caused damage to the spermatozoa, as reflected by an increase in the release of the amino acid oxidase (increased from 39.6 to 86.1% of that released from maximally damaged spermatozoa) and a reduction in the motility of the spermatozoa (reduced from 29.6 to 2.7% motility). Very little of the damage was incurred in the cooling of the spermatozoa to 5°C before freezing: this tends to suggest that the effect of seminal plasma on spermatozoa during freezing is distinct from its known effect in cold shock of spermatozoa.