Use and evolution of sperm sexing in cattle. Review

Since the commercial beginning of sperm sexing in artificial insemination, the adoption of this technology by the livestock industry (producers, veterinarians, and genetics companies) has been a reality in cattle production, mainly in dairy cattle. This review describes the beginnings of sperm sexing, its development, commercial application, and evolution to the present. The most significant events were undoubtedly the determination of the difference in DNA content between spermatozoa carrying the “Y” or “X” chromosome, the flow of these in the cytometer, and their separation into the so-called “Y” and “X” spermatozoa. The subsequent achievements that favored the application of this technology commercially were the determination of the optimal concentration and the successful cryopreservation of sexed semen; since then, research to try to reduce the deleterious effects of the sexing process has not stopped, leading to the emergence of new sperm sexing technologies where this effect is minimal. The most widely used technique commercially is the ultrasexing of 4 million spermatozoa (SexedULTRA-4M™), in which the method, media, and cytometers were completely modified so that this technology has results very similar to those obtained with unsexed semen (conventional semen). There is another sperm sexing technology called Sexcel™ that is offered commercially, in which they have obtained similar results to those obtained with conventional semen, but only in heifers. With these advances, sperm sexing is shown to be a technology in constant development and of high impact on cattle farming.