Livestock, a major component of agriculture sector, contributes 55.1 percent to agriculture value added and 11.5 percent to national GDP. Almost 35-40 million of rural population is engaged with livestock and its related activities. Rapid increase in human population and less milk production are among the main issues faced by Pakistan. Consequently, Pakistan has to import dry milk and other related products, which is seriously affecting the economy of the country. Therefore, it is need of the hour to improve the genetic potential of the existing dairy animals in order to meet future food demands. At present, Pakistan has 31.7 million buffalo population which contributes 68% of total milk produced in the country.
Artificial insemination with frozen semen is the most viable biotechnology to increase milk production of buffalo population. Frozen semen helps to improve genetics, preserve endangered species and easy import of genetic material. In Pakistan, rate of natural breeding in buffalo is very high as compared to artificial insemination due to easy availability of buffalo bulls in neighbourhood, un-availability of pedigreed bulls and poor conception rate with frozen semen. Low conception rate in Nili-Ravi buffalo with frozen semen may be due to higher acrosomal damage, reduced sperm motility and more alterations in sperm membrane integrity during semen cryopreservation as extenders used for buffalo semen cryopreservation are not compatible with buffalo semen.
It is believed that 50% sperm livability is dropped during semen cryopreservation due to osmotic stress, oxidative stress and cold-shock. Semen extenders used for buffalo semen cryopreservation ignore the osmolality requirements of buffalo semen. Preservation of buffalo semen in such an extender may expose spermatozoa to osmotic stress. Thus, along with other semen quality parameters, osmotic pressure of semen diluents can play key role during semen cryopreservation.
Oxidants level is another factor that can affect semen quality. A lower oxidants concentration is advantageous for spermatozoa physiological functions. Addition of antioxidants to semen reduces oxidative stress and improves post thaw semen quality. It is need of the hour to minimise sperm damages during cryopreservation by developing a suitable semen extender for buffalo semen cryopreservation. Keeping in view the above mentioned issues, a study to evaluate efficacy of different semen extenders, osmotic pressures and antioxidants on post thaw semen quality and pregnancy rates was conducted at UVAS. This study also supported earlier findings of the researchers that consideration of semen extender used along with its osmotic pressure and inclusion of butylated hydroxyl toluene improves post thaw semen quality.
DR FAZAL WADOOD
UVAS, Lahore