Evaluation of antifreeze protein III for cryopreservation of Nili-Ravi (Bubalus bubalis) buffalo bull sperm

Lower fertility in buffaloes with frozen-thawed semen is attributed to sperm damage that is believed to be due to formation of ice crystals during freeze/thaw process. It was hypothesized that antifreeze proteins in the extender may improve the post thaw quality of buffalo bull sperm. For this purpose, two separate experiments were conducted to evaluate antifreeze proteins III (AFP III) at 0 (control), 0.1, 1 and 10 μg/mL (Experiment I) and 0 (control), 0.01, 0.1 and 1 μg/mL (Experiment II) for its effect on post thaw quality of buffalo bull semen. Semen was collected from three Nili-Ravi buffalo (Bubalus bubalis) bulls with artificial vagina (42 °C) for three weeks (replicate) per experiment. For each experiment, qualifying ejaculates (6 ejaculates/bull) were divided into four aliquots and diluted (at 37 °C having 50 × 106 sperm/mL) in tris-citric acid extender containing above mentioned concentrations of AFP III. Diluted semen was cooled to 4 °C in 2 h, equilibrated for 4 h, filled in 0.5 mL straws, kept over liquid nitrogen vapors for 10 min and plunged in the liquid nitrogen. After 24 h of storage, semen straws were thawed at 37 °C for 30 s to assess sperm progressive motility (SM), plasma membrane integrity (PMI), viability (live sperm with intact acrosome) and normal epical ridge (NAR). In experiment I, improvement (P < 0.05) in percentage SM and sperm PMI was recorded in extender containing 0.1 μg/mL AFP III compared to control, the higher concentrations (1 μg/mL and 10 μg/mL) being inefficient. While evaluating the lower concentration (experiment II), 0.01 μg/mL of AFP III in the extender it was found to be ineffective to improve semen quality parameters, while 0.1 μg/mL AFP III in extender was found better in terms of progressive motility and plasma membrane integrity of buffalo bull semen compared to control. Sperm viability and NAR remained similar (P > 0.05) in extenders containing different concentrations of AFP III and control in both of experiments. In conclusion addition of AFP III in the extender at 0.1 μg/mL improved the progressive motility and plasma membrane integrity of cryopreserved buffalo bull semen.