Milk supplements in a glycerol free trehalose freezing extender enhanced cryosurvival of boar spermatozoa

ObjectiveTo evaluate the effect of skim milk and/or coconut milk in a glycerol-free trehalose extender to improve cryosurvival of boar spermatozoa.MethodsSperm samples were diluted in an egg-yolk-based freezing extender containing 100 mM trehalose and 0.25% Equex STM supplemented with coconut milk or/and skim milk at 2% or 5% (w/v). Spermatozoa were cryopreserved in 0.5 mL straws and thawed by a rapid transient method (at 70 °C for 8 s) followed with a stabilizing procedure at 39 °C. Thawed samples were analyzed for motility, viability, high mitochondrial membrane potential (HMMP), and acrosome damage.ResultsEven on the presence of egg yolk, motility, HMMP and viability were significantly higher in extender supplemented with 2% skim milk than controls without skim milk (P < 0.05). Post-thaw viability significantly improved with the addition of 2% skim milk plus 2% coconut milk as well (P < 0.05). Acrosome damage was considerably lower when the extender was supplemented with 2% coconut milk (P < 0.05), whereas the benefit was masked in the presence of 2% skim milk.Conclusion2% skim milk can be used as supplements for a glycerol-free trehalose and egg yolk-based extender to improve post-thaw survival of boar spermatozoa, whereas 2% coconut milk has an effect to protect boar spermatozoa from acrosome damage.