Use and evolution of sperm sexing in cattle. Review

From the beginning of commercial sperm sexing in artificial insemination, the adoption of this technology by the cattle industry (producers, veterinarians and genetics companies) has been a reality in bovine production, mainly in dairy cattle. This review is a description of 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 next achievements that favored the commercial application of this technology were the determination of the optimal concentration and the successful cryopreservation of the sexed semen; since then, research to try to diminish the deleterious effects of the sexing process did not stop, leading to the emergence of new sperm sexing technologies where this effect is minimal. The most widely commercially available technique is ultra-sexing of 4 million sperm (SexedULTRA-4M (TM)), in which the method, media and cytometers were completely modified, so that this technology has results very similar to those obtained with non-sexed semen (conventional semen). There is another sperm sexing technology called Sexcell (TM) that is offered commercially, in which similar results to those obtained with conventional semen have been obtained, but only in heifers. With these advances, sperm sexing is shown to be a technology in constant development and of high impact in cattle farming.