Freak giant calves and lambs have been born on experimental farms in Britain and America after an attempt to mass-produce herds of identical animals by cloning went disastrously wrong.
Instead of weighing the usual 80lb, several of the calves developed to 150lb or more in the womb, and had to be delivered by Caesarean section.
The research which led to the Frankenstein-like effect was pioneered in a government-funded laboratory in Cambridge, where scientists first discovered the problem after a cloned lamb was born double its normal birthweight.
The Milk Marketing Board has now withdrawn from an attempt to market the cloned embryos from a research farm in the north of England after receiving what it says was an early "signal" of the giant calf phenomenon.
The outsized births have shocked scientists, who have no idea of the cause or how to prevent it. The MMB and the Meat and Livestock Commission are funding intensive research into the techniques involved to try to resolve the freak effect.
Genus, a biotechnology and farm management subsidiary of the MMB, has scrapped a marketing project launched with an American company, Granada Biosciences, of Houston, Texas, which went into liquidation in January. It said the oversized animals were the last straw when it was already suffering from financial difficulties.
Granada had recruited Dr Steen Willadsen, who pioneered cloning while working at the Institute of Animal Physiology and Genetics Research in Cambridge, to develop the technique for mass marketing. Willadsen came to world attention several years ago when he announced the birth of the first geep - a half goat, half sheep - produced in his laboratory at Cambridge.
Using his methods, Granada impregnated nearly 1,000 cows with cloned embryos. But they became unsaleable after it was found that about one in five of the calves was emerging bigger than it should be, and one in 20 was a giant.
The calf clones have now been distributed to several American universities for detailed study. Scientists have noted that the giants end up only slightly bigger than normal adult cows.
Last week Dr George Seidel, professor of reproductive physiology at Colorado State University, who organised a conference on the new techniques in January, confirmed the freak effect.
He said the phenomenon was one of the most important discoveries in developmental biology in the past decade, rivalling cloning itself, and that laboratory manipulations of the embryos involved in cloning were likely to have caused the problem.
"Mistreating the egg for a short period may not cause problems, as it can repair itself. But if one insults the system for too long, something may go awry," said Seidel.
Dr David King, director of the Genetics Forum, a watchdog body set up to monitor genetic engineering and biotechnology research, warned that the giant calf phenomenon typified scientists' uncertainty and lack of understanding on some fundamental processes.
Cloning enables scientists to multiply a single embryo, in the laboratory, into theoretically unlimited numbers of genetically identical copies. The cloned embryos are nurtured in the laboratory for a few days until they are ready to be implanted into a cow, to be born nine months later.
Alternatively, they can each be split into duals, and implanted into more eggs, further multiplying the number of identical embryos.
Steve Amies, breeding production director for the Milk Marketing Board, defended its cloning research programme, which was aimed at meeting future demands for milk with specific qualities, such as a fixed ratio of protein to fat. "We are more likely to get a uniform product with cloning. Any problems involved along the way, such as large calves, is part of the research. The scientists don't know what is going to happen until they do it."
The phenomenon has intensified ethical doubts about manipulation of farm animals by scientists for the benefit of humans.
The Rev Dr Andrew Linzey, director of the theology centre at Essex University, said: "These are attempts to create animal machines that yield more milk or tastier meat or bigger profits. To manipulate their lives for these ends is morally grotesque. When the end result is freak animals, inevitably there will be additional suffering."
