Using sexed semen to boost genetic quality

Using sexed semen from carefully selected bulls can help farmers to expand and improve their herds extremely rapidly – but it’s not always straightforward, as Olivia Cooper discovers.

Guaranteeing a heifer calf from your best dairy cows can be an excellent way to improve herd productivity and boost replacement numbers. But sexed semen is not as cheap – or as fertile – as conventional semen, so is it worth using?

David Homer has used sexed semen on his herd of 220 pedigree Holsteins for more than 10 years, on and off. But a recent decision to create a second dairy herd sparked widespread use across 80% of his maiden heifers and about 30% of his milking cows. Farming with his son Chris and nephew James Major, he wanted to create two separate herds for the upcoming generation to take on.

The main unit, at Chisbury Lane Farm, Marlborough, Wiltshire, extends to 108ha, while the 154ha Park Farm caters for youngstock and dry cows. “The best cows in our herd are the ‘invisible’ ones that don’t have any issues,” he says. “Those are the ones we want to breed from.”

To get the best results, Mr Homer assesses his cows – which yield an average 10,000 litres a cow a year – and matches them up to the most suitable bulls.

“If the cow has a particular trait that needs improving we’ll use a sire that is strong in that area.” However, he bases his choice of sire primarily on its profitable lifetime index (PLI) score, which rates all the indices that impact on farm profitability. “In an ideal world, we wouldn’t use bulls with a PLI below 150,” he says.

In addition to the PLI, he examines the bloodlines, to avoid inbreeding, and considers breeding values for daughter fertility and cell count. “We are on a liquid contract so don’t need lots of butterfat and protein, and we don’t look for excessive increases in milk. We want good, commercial, long-living cows. Tall cows don’t fit our system, so we don’t use any sires with high-stature breeding values.”

Mr Major says using sexed semen is increasing the genetic gain and potential of the herd more quickly than conventional semen. “We’re breeding replacements from the best young females and also use quite a lot of young bulls to speed up the genetic progress.” The family now have 250 heifers ready to split off into the second herd, and will continue to use sexed semen to produce replacements. “We are also in a position to sell older cows or heifers, depending on what people are looking to buy.”

Although the technology has made great strides in recent years, cows’ conception rates with sexed semen are about 12% lower than conventional semen, says Mr Homer. “We use it very selectively, mostly on maiden heifers and cows that have a history of good fertility. You have to select the right cows in good condition, and if they’re heifers, are on a rising plane of nutrition.

“They must not be stressed in any way: if anything is wrong, or you’ve just housed them or changed the ration, don’t used sexed semen as it will be wasted. It’s also critical to have the correct thawing, water temperature and hygiene at the time of insemination – everything has to be spot on. But if you get it right, it is financially viable, and it definitely has an important role in our system.”

Sexed semen – crunching the numbers

When deciding whether to use sexed semen, farmers should consider the full financial implications, says Ian Powell at The Dairy Group.

“The cost of sexed semen varies enormously, from 160% of conventional to 360% – plus the number of straws you need will be higher. There is great benefit in being able to use beef bulls on the rest of the herd, with resulting higher calf values. But don’t compromise the quality of bulls just to use sexed semen; you may end up not making as much progress as you wanted to.”

In a worked example, using sexed semen to produce 50 heifers would net a gain of £2,323 a year, depending on the relative cost of sexed to conventional semen, the price difference between a Holstein bull calf and beef cross calves, and conception rates.

Top tips for using sexed semen

• Choose your best heifers or fertile cows

• Use bulls with the best PLI scores

• Ensure females are in good condition and stress free