Evolution of cervine, caprine and ovine sex-sorted semen processing

Abstract

It has been three decades since the first publication showing that flow cytometry was a reliable method to separate X and Y chromosome bearing sperm based on their difference in DNA content (Johnson et al., 1989). Ten years after that publication, the first commercial straw containing 2.1 x 106 frozen sex-sorted bovine sperm was released to the market for standard artificial insemination (Garner and Seidel, 2008). Several improvements have happened in the flow cytometry technology since that first commercial straw was released, such as the introduction of orienting nozzles, digital processing, multiple headed sorters, and automation, in a new generation of faster and more efficient sperm sorters known as Genesis (Sharpe and Evans, 2009; Evans, 2010). Significant enhancements in sperm handling, preparation for sorting and media composition have also allowed for sperm quality and conception rates of sex-sorted sperm to reach levels that are comparable with non-sorted (conventional) semen (Vishwanath et al., 2014; Vishwanath, 2014; González-Marín et al., 2018; de Graaf et al., 2014). The result is a complete overhaul of the conditions under which sperm is processed and sorted, known commercially as SexedULTRA™. Today, beef and dairy cattle sperm sorting laboratories are operating commercially in more than 25 locations, in 14 countries, with an annual production of more than eight million straws. In the past few years, small ruminant industries have been progressively testing and implementing the sperm sex-sorting technology for application in their specific environments. The demand for sheep and goat products has increased considerably worldwide since these small ruminants are easily managed, require a relatively small initial investment and their short generation interval lends itself to a fast return on investment for farmers. Also, dairy goat production keeps drawing the attention of producers due to the health benefits of milk and the popular cheeses and dips made from it. On the other hand, cervine industries have been slowly integrating sex-sorted sperm into their artificial insemination practices for antler trophy hunting and genetic improvement of the herds. Sex-sorted sperm will allow these growing industries to produce optimal proportions of males and females, improve herd management and increase the rate of genetic progress.