Effect of polyvinyl alcohol on survival and function of angora buck spermatozoa following cryopreservation

The aim of this study was to examine effects of polyvinyl alcohol (PVA) on buck semen quality. Seventy-five ejaculates were collected and diluted in Tris-egg yolk extender containing one of three PVA co-polymers of 9, 18 and 100 kDa. Five different concentrations 0.001, 0.01, 0.1, 1 and 2% of the PVA co-polymers were added to the extender with respected to the decreasing glycerol concentrations of 5, 4, 3, 3, 2% respectively. Following freeze-thaw, sperm motility, viability, acrosome-intact spermatozoa and mitochondrial membrane potentials were analysed. During freezing, sperm seeding temperature were recorded with a cryo-thermometer. PVA 2% glycerol group gained 8.2 ± 1 °C latent heat plateau difference comparing to control. Highest motility was found in PVA 18 kDa with regardless of the dosage (P < 0.001). All PVA copolymers gained higher motility independently in all other dosage groups (except PVA 2%) comparing to control (P < 0.001). Live spermatozoa rate between treatment groups were statistically insignificant (P = 0.953), however, when moribund sperm were gated out PVA 9 induced better protection with respect to other groups (P < 0.05). Intact acrosome rate was statically higher in PVA groups (P < 0.002) and subgroups (P < 0.001). Mitochondrial membrane potential was higher in all experimental groups comparing to control group (P < 0.001). PVA co-polymer concentrations of 0.01, 0.1, 1 and 2% v/v (PBS: PVA) decreased the concentration of glycerol required for freezing in a 100 ml volume by 0, 1, 2, 2, and 3% v/v from the control dose (5%), respectively. In conclusion, synthetic PVA-derived ice blocking agents offer new opportunities for improving the post-thaw buck sperm quality.