Effects of coconut milk alone or supplementation with pyridoxine in tris-extenders on viability of buck spermatozoa during vitrification

• Cryosurvival of sperm with coconut milk studied.
• Cryosurvival of sperm with coconut milk supplemented with pyridoxine.
• Cryopreserved semen samples for 30 days evaluated for sperm viability.
• Acrosome reaction and capacitation of spermatozoa were induced in vitro.
• Sperm viability improved with coconut milk alone or supplementation with pyridoxine.
• Acrosome reaction and capacitation improved with coconut milk alone or supplementation with pyridoxine.

The effects of coconut milk alone or supplementation with pyridoxine in tris-extenders on viability of spermatozoa obtained from West African Dwarf (WAD) goat bucks during vitrification were evaluated in two studies. In study I, semen samples were diluted with different levels of coconut milk (0, 5, 10, 15 and 20 mL/100 mL of diluent) in tris-extenders, while in study II, semen samples were diluted with tris-coconut milk extenders and supplemented with different levels (0, 2, 4, 6 and 8 mM) of pyridoxine. Sperm were vitrified and stored for 30 days and thereafter evaluated for sperm quality characteristics. Following vitrification, acrosome reaction and capacitation of spermatozoa were induced in vitro. The results showed higher (P < 0.05) viability parameters and lower (P < 0.05) percentage abnormalities and malondialdehyde (MDA) concentrations in coconut milk extenders compared to the control. In addition, higher (P < 0.05) percent of spermatozoa underwent acrosome reaction and capacitation in coconut milk extenders compared to the control. Improvement in these parameters was optimal at 15% and 20% of coconut milk extenders. Higher arginase activity (P < 0.05) was observed at 20% of coconut milk extenders. Similarly, higher (P < 0.05) viability parameters, and lower (P < 0.05) percentage abnormalities and MDA concentrations were observed in tris-coconut milk extenders supplemented with pyridoxine compared to the control. Spermatozoa vitrified with 8 mM of pyridoxine supplementation had higher (P < 0.05) percentage acrosome integrity and membrane integrity, and arginase activity compared to other treatments and the control. The results showed that vitrified spermatozoa had higher (P < 0.05) acrosome reaction and capacitation in tris-coconut milk extenders supplemented with pyridoxine compared to the control. Optimal improvement in these parameters was obtained in tris-coconut milk extenders supplemented with 8 mM of pyridoxine. The findings revealed that inclusion of coconut milk at 15% and 20% in tris-extenders or supplementation of tris-coconut milk extender with pyridoxine at 8 mM consistently improved sperm viability parameters of WAD goat bucks during vitrification.