The technique is likely to put an end to the birth of 600,000 unwanted dairy bulls a year. The benefits to milk farmers are expected to be considerable. They will not waste money on male cattle, and will instead be able to rear greater numbers of milk-producing females.
The separation technique is expected to revolutionise the milk production of Britain's 30,000 dairy farmers, and put an end to the routine slaughter of dairy bulls.
The method is likely to intensify the debate over whether it is ethically right for humans to seek to pre-determine the sex of their children. Although the separation of male and female chromosomes does not amount to cloning, human "sperm engineering", which is banned in the United Kingdom, has raised the spectre of "off-the-shelf" babies.
Three cows, Chloe, Clover and Charity, were born using the new technique on a farm in Cheshire last month. Commercial operations will be established within two years. The male and female chromosomes were separated by an advanced screening process that creates a 90 per cent likelihood of producing a female calf - far greater than the traditional 50-50 chance offered by nature. The technology was created by Cogent, an English cattle breeding company, which represents 3,700 UK dairy farmers in partnership with XY Inc, a sister company based in Colorado.
"This is an extraordinary development in the history of cattle breeding," said Martin Hall, a spokesman for Cogent. "It's something that dairy farmers have wanted for years."
Dairy farmers have long dreamt of developing a method to guarantee their animals produce more female than male calves. Dairy bulls rarely make good quality beef, and it is not economically viable for most dairy farmers to fatten up the muscle of a dairy cow so it can be sold for beef.
Until two years ago, the majority of unwanted bull-calves were sent abroad for sale as veal. But the BSE crisis, coupled with sustained animal rights protests, led to the trade being halted. Now bull-calves are simply killed and incinerated at the age of two weeks, with the help of a pounds 28m subsidy from the Ministry of Agriculture, Fisheries and Food.
The new technique will mean these bulls will not be born in the first place. The sperm screening developed by Cogent separates the female-producing X and male-producing Y chromosomes by a filtration method in which each single sperm is isolated in droplets of water. A cell-sorting machine identifies the sex of each droplet - "female" sperm carries more DNA than "male" sperm - and a small electrical charge is added as it passes through a magnetic field, allowing male sperm to assemble separately. The technique is 90 per cent accurate.
The National Farmers Union has welcomed the breakthrough, which it hopes will increase efficiency and productivity among dairy farmers. "It's a step forward. There are management and animal welfare benefits," said Stephen Rossides, head of livestock for the NFU. "At the moment it's a bit of a lottery."
Attempts to pre-determine the sex of human babies has generated greater ethical uncertainty. Gender selection of embryos for social reasons is banned in the UK, except for medical reasons. But last year two couples exploited a loophole by sending their sperm to the US for screening.
Paul Rainsbury, medical director of the Bupa Roding Hospital in Ilford, Essex, which is assisting couples hoping for a baby, said that veterinary advances usually preceded similar developments with humans: " NThe first test tube baby is now 21 and her birth came as a result of research in the animal kingdom."
He did not believe ethical arguments applied to sperm engineering. "We are no more playing with God than the surgeon who removes an appendix."Reuse content