Effect of post-thawing incubation on sperm motility and acrosomal integrity of cryopreserved Garole ram semen

The Garole is a prolific, but less well known small Indian sheep breed found in the hot and humid Sunderban region of West Bengal. A recent finding based on DNA tests provides new evidence that the major gene for prolifacy (FecB) in Booroola Merino strain was introduced from the Garole sheep. The breed has been shown to have the potential to perform well in a semi-arid tropical climate and could serve as a source of valuable germplasm for incorporating prolificacy traits in the monotocus breeds of semi-arid and tropical regions of India. The aim of the present study was to evaluate sperm motility characteristics and acrosomal integrity of Garole ram spermatozoa cryopreserved under controlled conditions and subjected to a 4 h post-thawing thermal evaluation test. Diluted semen samples were packaged in mini size straws and cryopreserved under controlled conditions using a programmable freezer. The frozen straws were thawed at 50 °C for 10 s and incubated at 37 °C for 4 h. Sperm motility characteristics and acrosomal integrity were evaluated at hourly intervals following incubation. Prior to incubation, the mean motility and spermatozoa with intact acrosomes was 77.8 and 64.7%, respectively. There was a progressive decline in the percentage motility and percentage normal acrosomes over time. The post-thawing incubation had a significant (P < 0.05) effect on motility and percentage of spermatozoa with normal acrosomes. After 4 h of incubation, the motility and spermatozoa with intact acrosomes was 56.5 and 56.7%, respectively. The effect of replication on post-thawing incubation was significant (P < 0.5) on motility, but not on the acrosomal integrity of spermatozoa. The information generated in this study could be useful for ex situ preservation of Garole ram spermatozoa in straws under controlled conditions for use in artificial insemination.