Fresh semen tops

Teagasc researchers are developing computer models to predict the economic impact of using sexed semen in heifers and lactating cows on Irish dairy farms.

Their findings suggest the most rapid growth in the national herd would result from using fresh sexed semen rather than frozen-thawed sexed semen, or frozen-thawed conventional semen.

“The potential increase in availability of replacement heifers could be vital if we are to expand cow numbers in order to achieve the 50% increase in milk output targeted in Food Harvest 2020, the Department of Agriculture, Food and the Marine’s strategy for Irish agriculture,” said Dr Stephen Butler of the Animal and Grassland Innovation Programme, Moorepark, in a recent Todays Farm magazine report.

Commercially available sexed semen offers farmers the opportunity to choose the sex of the calf, which would obviously be hugely beneficial within a breeding strategy.

Dairy farmers currently decide how many replacements they need for their herd and serve an appropriate number of cows with dairy genetics.

Roughly five straws are currently used per heifer that will enter the herd.

Male dairy calves, with limited potential as beef animals, are an inevitable by-product. With sexed semen, dairy farmers could potentially produce a heifer from almost every cow in the herd, because sexed semen is about 90% accurate. As well as reducing the number of male dairy calves, this would allow rapid expansion of milk production if required.

Alternatively, farmers could use dairy genetics with sexed semen on relatively few cows — the best — secure in the knowledge that they will produce about 90% daughters.

Beef suckler farmers using AI could benefit from sexed semen by opting for a higher proportion of male calves.

But how close is the practical use of sexed semen? “Fluorescence-Activated Cell Sorting is able to separate male and female sperm, based on the fact that female producing sperm has slightly more DNA,” said Dr Ian Hutchinson at Teagasc Moorepark. “This process is approximately 90% accurate.”

There are catches. Sorting the sperm is slow and many sperm are lost or damaged. Sexed semen is costly (€18 more per straw) and conception rates are lower.