31 March 2000

Sexed semen has lots to offer dairy and hill sheep

By Jessica Buss

WHEN sexed semen becomes available it will enhance production efficiency and be a milestone in tailoring production more closely to market needs.

Tom McEvoy of SAC Aberdeen told delegates at a BSAS session on semen sexing that the dairy and hill sheep sectors were likely to see most benefit. But Dr McEvoy said question marks remained over costs and price. "Many say it will be five years before it is commercially available."

Also speaking at the session Rupert Amann, of BioPore in the USA, said sexed semen costs needed to be £7.50 a dose and conception rates improve for it to be used widely for AI.

"For IVF and embryo transfer sexed semen is cost-effective now," added Prof Amann.

But he estimated sexed semen production costs at nearer £22-£25 a dose above semen cost, if sort rates could be increased to 4000 sperm a second. But savings from reduced calving difficulties would be worth £17.50 a heifer on average.

David Cran, SAC Aberdeen and adviser to XY, which developed the flow cytometry system in use at Cogent, Cheshire, hoped sort rates would soon reach 4000 sperm a second at 95% accuracy.

"Improvement in sorting has resulted in sort rates of 2500 sperm a second and we are confident they will be up to 4000/second in six to eight months."

Dr Cran also reported pregnancy rates with frozen sorted sperm had reached 85 to 90% of controls using conventional frozen semen in recent studies. Pregnancies had been achieved and animals born, he added.

But Cogent, which claims to be the only organisation with calves born using sexed semen, told farmers weekly that it expected its sorted sperm to become available to dairy farmers this year at an affordable cost.

An extensive field trial involving 2500 heifers on farms in north-west England started this month, added the company.

When sexed semen does become available to the dairy industry, Dr McEvoy believes it will have short and long-term benefits.

It will cut the number of dairy bulls born and mean that only the top 40% of herds are used to breed replacements, increasing genetic progress. Remaining cows are then used to produce higher value beef cross calves or if sexed beef semen was used, beef cross bulls, he added.

Concerns over increased calving difficulties may be misplaced, he said. "Heifers would be the highest merit animals, so would be bred pure, avoiding calving difficulties. Older animals would give birth to bulls, causing less concern over calving difficulty."

But conception rates achieved would remain an issue. "Dairy herd fertility is already poor and we cannot cope with a further reduction." Trials on sexed semen so far had only involved heifers and the conception rate possible on less fertile cows was yet to be proven, warned Dr McEvoy.

The other sector with much to gain from sexed semen would be hill sheep production, he said.

"Hill ewe numbers are high, and male lambs could be better in terms of meat products." These male lambs are a by-product of the hill sheep flock.

But sexing sperm and using AI would allow ewes to produce only females from a smaller flock. Alternatively, producers could maintain flock numbers, breeding some female replacements and using a terminal sire to produce higher quality lambs from remaining ewes.

But using AI in sheep was not feasible on a commercial scale without further developments in the techniques used, he added. &#42

SEXEDSEMEN

&#8226 Could be available soon.

&#8226 Sort rates increasing.

&#8226 Sheep and dairy benefits.

Sexed semen has much to offer dairy and hill sheep producers, says Tom McEvoy.