DESPITE the fact that the first calves produced using sexed semen straws were born in 1999, this technique is still constantly evolving and is now greatly improved, more widely available and more popular than ever before. In the 12 months preceding March 2020, sexed semen represented 51.3 percent of all semen purchased, a jump of almost 20 percent from the previous year, and almost 35 percent from 2017. Sexed semen is produced by identifying which sperm cells carry an X- and which carry a Y-chromosome. The X-chromosome (female) carries around four percent more DNA than the Y-chromosome (male) in cattle, and it is this difference that allows the sorting and categorisation of the sperm cells.

So, what are the consequences of using sexed semen in the dairy industry?

Advantages: More Female Calves Can Decrease Costs & Increase Profits· Can produce a sex ratio of close to 90 percent favouring female offspring· Fewer unwanted males produced, coupled with only rearing the heifers which are needed, reducing rearing costs· Increased supply of replacement heifers facilitates faster and more profitable dairy herd expansion· Opportunity to sell surplus heifers to other farmers. Greater Level of Control:· Ability to choose the number served with sexed semen to produce specific number of replacement heifers necessary· Can breed highest performing animals with the best available bulls and be confident in gaining a replacement· The rest can be inseminated with beef sires to produce a calf required by the beef market which can increase profit. Biosecurity: · Removes the risk of introducing disease into the herd by purchasing heifers from elsewhere· Allows maintenance of a closed herd. Genetic Improvement: · Sexed semen may accelerate the rate of genetic gain as it allows selection of highest ranked dairy cows from which to breed replacements· Can be emphasised further if replacements exclusively bred from maiden heifers which should have the highest genetic merit in the herd. Disadvantages: More expensive than conventional semen· This may be off putting although, as beef semen is generally cheaper than conventional dairy, the increase in cost may not be as drastic as first thought if more are put to beef sires· The premium price paid has recently decreased as it becomes more widely available. Potential for Reduced Fertility· Decreases of 10-15 percent have been reported when compared with conventional semen, possibly due to lower doses of sperm per straw however, in contrast, reports of almost identical conception rates have been made by some farmers more recently with advances in technology· Increased fragility due to having undergone manipulations means more care might be needed when selecting recipient cows and also when performing artificial insemination. Not 100 percent accurate· Sex ratio of 90 percent favouring female offspring but this means success is not a guarantee.