Update on sexed semen technology in cattle

Abstract

The technology in current use for sexing sperm represents remarkable feats of engineering. These flow cytometer/cell sorters can make over 30 000 consecutive evaluations of individual sperm each second for each nozzle and sort the sperm into three containers: X-sperm, Y-sperm and unsexable plus dead sperm. Even at these speeds it is not economical to package sperm at standard numbers per inseminate. However, with excellent management, pregnancy rates in cattle with 2 million sexed sperm per insemination dose are about 80% of those with conventional semen at normal sperm doses. This lowered fertility, in part due to damage to sperm during sorting, plus the extra cost of sexed semen limits the applications that are economically feasible. Even so, on the order of 2 million doses of bovine semen are sexed annually in the United States. The main application is for dairy heifers to have heifer calves, either for herd expansion or for sale as replacements, often for eventual export. Breeders of purebred cattle often use sexed semen for specific matings; thawing and then sexing frozen semen and immediately using the few resulting sexed sperm for in vitro fertilization is done with increasing frequency. Beef cattle producers are starting to use sexed semen to produce crossbred female replacements. Proprietary improvements in sperm sexing procedures, implemented in 2013, are claimed to improve fertility between 4 and 6 percentage points, or about 10%.Keywords: sexed semen, cattle, fertility, economics ImplicationsOver the next few years, it is unlikely that any fundamentally new technology will become available for sexing sperm commercially. However, incremental improvements in flow cytometer/cell sorting procedures almost certainly will result in faster speeds of sexing sperm and improved fertility. However, fertility of sexed semen is unlikely to exceed 90% of unsexed semen for most situations for several years, so profitable applications for cattle will be limited. Longer term prospects are encouraging; since sperm are evaluated one at a time, some defective sperm are discarded during sexing, and this may become more sophisticated, increasing fertility. IntroductionMost companies and cooperatives selling bovine semen in the United States sell sexed semen from a subset of their bulls. For reasons to be explained later, it is impossible to know the precise volume of sexed semen sales, but a consensus figure is on the order of 2 million doses annually, averaged over beef and dairy sires and domestic and export sales. This represents something < 5% of bovine semen sales volume.To interpret the sexed semen industry, it will be useful to consider a bit of history plus some intellectual property issues. Sexing sperm is still a developing technology, so changes in the product continue to be made, such as improving fertility, increasing accuracy of sexing, adding flexibility to delivery systems and reducing costs. Intellectual property issuesThere is only one useable, reasonably accurate method of sexing mammalian sperm availab...

Will AI in pigs become more efficient?

“…Certainly, even in the best current scenario, using high-speed flow cytometers, the number of X or Y sperm separated with a purity above 90% hardly exceeds 20 million per hour [42]. This separation speed is acceptable to produce bovine AI-dose, usually of 2 millions per AIdose when sex-sorted sperm are used [43], but not to produce porcine AI-doses, that must contain at least 500 million sperm. Consequently, enhancing the efficiency of the current procedure is a challenge for the practical use of sex-sorted sperm in commercial swine AI programs.…”

Modern Reproductive Technologies to Improve Cattle Production

“…Today, approximately 2 million units of bovine semen containing sexed sperm cells are sold annually (Seidel 2014).…”

“…Pregnancy rates after AI with sex-sorted spermatozoa are typically 80% of those obtained after AI with traditional (non-sex sorted) semen from the same bull (Seidel 2014). For example, if pregnancy rate after AI with traditional semen is 60%, insemination with sex-sorted spermatozoa is expected to yield a 48% pregnancy rate (60% normal pregnancy rate X 80% fertility with sex-sorted semen = 48% pregnancy rate).…”

Practical implications of sperm selection techniques for improving reproduction

“…This decline may be partly due to negative energy balance in high yielding dairy cows (Diskin and Morris, 2008), but other factors may also be involved. For example, the number of bull spermatozoa included in an insemination dose has decreased, especially for sexed sperm samples (Seidel, 2014); two million spermatozoa may not be sufficient to give good pregnancy rates for all bulls (Andersson et al, 2004). In addition, changes have been made to freezing protocols, such as the avoidance of extenders containing egg yolk (Leite et al, 2010;Röpke et al, 2011) and increasing pre-freezing equilibration times (Leite et al, 2010;Shahverdi et al, 2014).…”