Enrichment of bovine semen with x-bearing spermatozoa using Percoll™ and Optiprep ® discontinuous gradients

In cattle, sex selection has a significant economic impact when it improves herd capacity of milk or meat production. Density gradient centrifugation might be an approach to sexing spermatozoa because of the additional DNA content and volume of X-bearing sperm head. In the present work, the accuracy of sperm sexing by Percoll™ and OptiPrep® gradients centrifugation was compared. Bovine semen from three breeds (Holstein, Gir, and Red Angus) was used. The sperm viability and sexing accuracy after sperm selection by centrifugation of low and high-density discontinuous gradient composed by three layers of Percoll™ or OptiPrep® were assessed by in vitro embryo production (IVP) and pregnancy rate following artificial insemination (AI). After IVP, cleavage rate was higher (P < 0.05) for unsexed (81.3%) than for sexed (75.5%) spermatozoa. A significantly lower cleavage rate was observed for sexed (76.1%) spermatozoa when compared to sexed Red Angus (81.2%) spermatozoa. Additionally, significantly lower blastocyst rate was observed using Holstein sexed sperm by OptiPrep® gradient (23.3%) when compared with Gir (41.9%) and Red Angus (48.7%) sexed sperm by Percoll™ gradient. Nevertheless, in all breeds analyzed, a significant sex ratio deviation to females was observed. Analyzing the pregnancy rate after AI with sexed sperm by Percoll™ and OptiPrep®, semen from Gir bulls presented lower (P <0.05) pregnancy/AI (61.3%)when compared to Red Angus (75.9%) and Holstein (77.4%) and bulls. From the results, it was concluded that the increase in female percentage after insemination and/or IVP with bovine sexed sperm by centrifugation of high density gradient composed by three layers of Percoll™ and OptiPrep® may allow this spermatozoa sexing technique to be used in large scale which would support genetic enhancement for milk and meat production as well as for progeny tests in cattle.