Abstract:
OBJECTIVE: To evaluate the effects of semen collection methods and different cooling rates on cooled and frozen-thawed Saanen goat semen. METHODS: Twenty bucks were divided into two groups of 10 animals per group based on semen collection methods: artificial vagina and electro-ejaculator. Samples from each collection method were pooled and diluted with Tris-based extender. The pooled semen was divided into two cooling methods: slow cooling and fast cooling. Sperm motility and velocity, sperm plasma membrane integrity, sperm viability, mitochondrial membrane potential and DNA integrity were evaluated before dilution, immediately after cooling at 4 °C and at 24 h after freezing by using computer assisted sperm analyser method and epifluorescence microscope. RESULTS: Mean values for total motility, rapid-speed and progressive motile spermatozoa were significantly higher in semen collected with artificial vagina than electro-ejaculator (P<0.001). Slow cooling resulted in higher percentages of total motile, rapid-speed and progressive motile spermatozoa as compared to fast cooling (P<0.05). The post-thaw percentage of rapid-speed spermatozoa collected by artificial vagina in slow cooled sperm was significantly higher as compared to electro-ejaculator method (P<0.05). The mean values of curvilinear velocity and straight-line velocity were significantly higher in slow cooled semen obtained by artificial vagina (P<0.001). Similarly, the combination of artificial vagina and slow cooling resulted in significantly higher post-thaw percentages of straight-line velocity, average-path velocity, sperm plasma membrane integrity, viability and acrosome integrity (P<0.01). No significant differences were observed in slow cooling between artificial vagina and electro-ejaculator in terms of post-thaw sperm mitochondrial membrane potential and DNA integrity (P>0.05). CONCLUSIONS: The use of artificial vagina and slow cooling rate in cryopreservation protocol improves the cooled and post-thaw sperm quality of Saanen buck semen.
