Effects of Thawing Methods (Techniques) on Freeze Thaw Buffalo Bull Sperm Quality

BACKGROUND: Semen cryopreservation involves preserving the sperms so they can be used later. This technique can prove to be a pathway for restoring the number of endangered species as their sperm can be preserved and used for fertilization later on. Objective: The propose of study is to find out the optimum thawing time, temperature and post thaw incubation period of cryopreserved buffalo sperm. Methods: Three buffalo bulls of the 1-2 year age were selected at Semen Production Unit, Qadirabad, Pakistan. Semen was collected by artificial vagina at 42 degrees C and 18 qualified ejaculates (two ejaculates/bull/week) for 3 weeks (replicate) were cryopreserved following a standard protocol. Frozen semen was divided in different groups, with each group being thawed at different temperature and time. Group I was subjected to slow thawing at 4-5 degrees C, 2nd group to moderate thawing at 35 degrees C-37 degrees C , 3rd group to rapid thawing while the 4th one was subjected to air thawing. Moreover, optimum incubation period of cryopreserved sperm was evaluated by thawing and incubating 42 straws in a water bath at 37 degrees C in with 2 straws being assessed every hour up till 10 hours. Results: Thawed semen samples were assessed based on different semen quality parameters. Acrosome integrity, plasma membrane integrity and progressive motility of cryopreserved buffalo sperm were significantly higher (P<0.05) in Group II which was subjected to moderate thawing. However, sperm quality parameters remained same (P> 0.05) with different incubation time (from 1 hr to 11 hr at 37 degrees C). Conclusion: In conclusion, moderate thawing is effective in protecting the sperm cell from freeze thaw damages during cryopreservation. Sperm functional quality parameters were very acceptable after even 5 h of incubation indicated the usefulness of these incubated semen straws for field insemination in areas where availability of liquid nitrogen containers is problematic. Digital thermos maintained at 37 degrees C could be alternative for short distance travelling for taking semen doses at insemination site. Further research efforts are needed to verify the fertilizing ability of this straw incubated (37 degrees C) semen.