In Pakistan buffalo is the main milk producing animal. Proven buffalo bulls are small in number and at the same time semen volume and sperm concentration is also low as compared to cattle. The major problem from the reproductive point of view seems to be low fertility (33%) particularly when being inseminated with frozen semen.
The most probable causes are mechanical and chemical damages to the spermatozoa during cryopreservation processes particularly motion characteristics and morphological changes (e.g., plasma membrane and acrosomal integrity) which cause a consequent reduction in the sufficient number of viable sperm cells at the site of fertilization. All these parameters are prone to oxidative changes which occur during the cryopreservation of semen. A minimum loss of spermatozoa during semen processing can be the only option for optimal use of the few elite buffalo bulls. Addition of any suitable antioxidant like ALA to the semen extender might be helpful in reducing these causes and will ultimately improve reproductive efficiency of buffalo bulls used in AI.
In this study, semen from healthy Nili Ravi buffalo bulls (n=5) was collected by artificial vagina and subjected to the different inclusion levels of ALA @ 0.50mM, 1.00mM, 2.00mM, 3.00.0mM, and 4.00mM. One group (control) received zero inclusion level of ALA. Semen was evaluated, diluted, cooled, filled in 0.5ml straws, equilibrated at 4°C for 4 hours and frozen in liquid nitrogen.
After storage and transportation to the Physiology Laboratory of UVAS, semen was thawed and evaluated for percentage motility of spermatozoa, plasma membrane integrity (HOST assay), acrosomal integrity (NAR) and vitality (Live/Dead). Five straws from each ALA treatment group were thawed individually in water bath at 37°C for 30 seconds and evaluated for quality parameters. The data collected was presented as cells ± SE and treatment groups were compared using one way analysis of variance. The group differences were compared by using the Duncan Multiple Range Test. The results of this study revealed that addition of 0.50mM ALA in semen extender may be useful from the cryopreservation point of view.
In conclusion addition of 0.50mM ALA in semen extender improved post-thawed semen quality in terms of spermatozoa motility and plasma membrane integrity, which indicates that the importance of an antioxidant in semen extender can not be neglected.