X-sperm Enrichment of Bovine Semen by Percoll Density Gradient Method and Its Effect on Semen Quality, Sex Ratio and Conception Rate

Abstract

In cattle, sex selection has a significant economic impact when it improves herd capacity of milk or meat production and is commonly used for the production of calves of the desired gender. New separation techniques which present both better accuracy and low costs are necessary. Density gradient centrifugation might be an approach to sexing spermatozoa because of the additional DNA content and volume of X-bearing sperm head. The present study was designed to apply the modified percoll discontinuous density gradient for X-sperm enrichment in cross bred bovine semen. We attempted to amplify the level of X-sperm enrichment by using double centrifugation in percoll gradient. In addition, effect of percoll density gradient on fertility of semen was also evaluated at three stages; before centrifugation (stage I), after 1st centrifugation (stage II) and after 2nd centrifugation (stage III) respectively and ultrasonography was carried out to confirm the sex of fetus at 60-90 days post AI. Semen was collected from two cross bred bovine bulls and 34 cows were inseminated with liquid X-sperm enriched semen after double centrifugation in percoll gradient. 22 cows were inseminated with non-sexed fresh liquid semen (control). Results showed that the volume, progressive motility, live sperms, concentration and HOST reactive sperms significantly (P is less than 0.05) decreased at stage II and stage III compared to stage I. However, no significant (P is greater than 0.05) change was observed in pH and mass motility of semen at all three stages. There was non-significant effect on per cent spermatozoa with intact acrosomal membrane and fully damaged acrosomal membrane at all three stages however, partially damaged acrosomal membrane sperms were significantly (P is less than 0.05) decreased at Stage II and Stage III compared to Stage I. The conception rate significantly (P is less than 0.05) decreased with X-enriched semen (41.17%) compared to non-sexed liquid semen (59.09%). The female sex ratio of calves significantly (P is less than 0.05) increased to 66.66% with X- sperm enriched semen compared to the male percentage of 33.33% with sexed semen and female percentage of 46.15% with non-sexed semen.