Effect of linoleic acid albumin in a dilution solution and long-term equilibration for freezing of bovine spermatozoa with poor freezability

Despite normal eucrasia, mating desire and semen quality, sire bulls sometimes have spermatozoa with poor freezing tolerance. This study assessed effects of the addition of linoleic acid albumin (LAA) and long-term (LT) equilibrium to frozen semen on their sperm freezing tolerance. Immediately after collection using an artificial vagina and a breeding mount, semen was diluted with yolk citrate buffer; then, it was cooled slowly to 4°C during more than 5 h. Equilibrium treatment at 4°C was applied using the same extender supplemented with glycerol. Semen of bull A, with low sperm freezing tolerance, was treated with 1 mg/ml of LAA added to the first extender. The equilibrium treatment at 4°C was prolonged to 30 h. Significantly higher motility rates were obtained for the LT + LAA-treated sperm before and after freezing-thawing. However, for semen of bulls B and C with normal sperm freezing tolerance, the LT + LAA treatment barely exhibited a small effect on the motility rate. Almost no difference was found among bulls A, B and C in the motility rates of LT + LAA-treated sperm after freezing-thawing. No difference of fertility was apparent on LT + LAA-treated frozen sperm in comparison with normal sperm in embryonic collection and in vitro fertilization. It was not an aberration of fertility in vivo or in vitro. In addition, the conception rate of artificial insemination did not have a difference, and a normal calf was obtained. Results show that addition of LAA to an extender for frozen bovine spermatozoa and 30 h of low-temperature equilibrium might improve the motility of freezing-thawing spermatozoa with poor freezability. Sperm exhibited normal fertilization capability and ontogenic capability.