A serious international commercial battle is in the offing as companies compete to exploit the possibilities and the latest part of the struggle takes the form of a calf - cloned using the technique that helped produce Dolly the sheep.
By cloning an embryo cell, scientists in the US have created Mr Jefferson - a 98lb (44.5kg) Holstein.
Born on 16 February, Mr Jefferson (named after President Jefferson, as it was born on Presidents' Day) was produced by the American subsidiary of PPL Therapeutics, which has been closely involved with the Roslin Institute near Edinburgh, where Dolly was born in 1996.
The latest work is not in itself a scientific breakthrough. But it marks an important commercial step forward in "pharming" - the use of farm animals to produce commercially valuable drugs. That will be done by adding human or other genes to the animals.
PPL already has a flock of such "transgenic" sheep which produce a protein in their milk used to fight cystic fibrosis in humans, and last year it produced "Polly" - a transgenic cloned sheep carrying the human gene for the production of the blood-clotting agent Factor IX, which could help haemophiliacs.
But two other American companies also claim to have cloned cattle. Last August, scientists at ABS Global Inc. in Wisconsin announced that they had been first to clone a calf - a Holstein named Gene. And last month scientists announced in Boston that they had developed a technique for producing customised cloned calves. Steven Stice and James Rohl of Advanced Cell Technology, told a conference that 13 cows are waiting to give birth to cloned calves at a ranch in Texas.
But nobody outside ABS Global or ACT knows what technique they used. The Roslin Institute has applied for patents around the world on its "nuclear transfer" technique - moving the DNA from a cell into an egg cell from which the nucleus has been removed.
If ABS Global and ACT have used the same technique, the Roslin Institute may have a prior claim, and be able to claim licensing fees.
So far, only PPL has been licensed by the Roslin Institute to use the nuclear transfer technique. The main potential of cloned cattle is to produce large quantities of human serum albumin, used mainly in trauma patients. At present hospitals rely on donated blood.
The difficulty of cloning adult cells compared to embryo cells has led some scientists to claim that Dolly was the result of a embryo cell in the sheep's blood. But Dr Harry Griffin a senior scientist at the Institute said yesterday the chances of this having happened were "one in several million".