Effects of addition of vitamin B12 to the extender on post-thaw motility, acrosome morphology, and plasma membrane integrity in bull semen

To investigate the effects of supplementation of vitamin B12 on bovine sperm post-thaw quality, vitamin B12 was added at the concentrations of 1.25, 2.50, 3.75, and 5.00 mg/mL to bovine semen cryoprotective medium. The results indicated that the motility and VSL, VCL, STR, and VAP values of sperm supplemented with 2.50 mg/mL vitamin B12 were significantly higher than those of other concentrations (P < 0.05). No significant difference was observed for LIN and ALH values and the percentage of grade a spermatozoa between the extenders containing 2.50 mg/mL and 3.75 mg/mL vitamin B12 (P > 0.05). The percentages of acrosome-intact and plasma membrane-intact spermatozoa were significantly improved (P < 0.05) by supplementing with 2.50 mg/mL vitamin B12. With all parameters measured, the concentration of 2.50 mg/mL vitamin B12 showed the best results on the quality of bovine semen in freezing-thawing. In conclusion, the addition of 2.50 mg/mL vitamin B12 to the extender improved the bovine frozen semen quality.