Research to overcome cloning flaws continues
Research to overcome cloning flaws continues
By Marianne Curtis
THE ability to breed identical copies of top performing livestock is still some way into the future, but research is underway to overcome the problems associated with cloning.
Ian Wilmut, whose work at the Roslin Institute led to the birth of Dolly the cloned sheep, told an RSPCA welfare conference in London last week: "Farmers couldnt consider using cloning at present because it is not economic. There are also problems with animals giving birth."
The technique provides the possibility of breeding duplicates of superior animals. It involves putting copies of the genes of animals with preferred characteristics into surrogates via embryo transfer, but is also currently associated with heavy losses during pregnancy and around the time of birth said Prof Wilmut. "In sheep, from day 50 of pregnancy to term, loss of embryos is 10 times higher in sheep carrying cloned embryos than in the conventional flock and 20% of the lambs die after birth."
Deaths around birth occur because surrogates have a longer gestation and tend to produce large offspring which are more susceptible to abnormalities. A research project at Roslin is looking at why these difficulties occur.
If and when cloning is available to livestock producers, safeguards need to be adopted to ensure that animals do not become too inbred. The Farm Animal Welfare Councils recent report on cloning expresses concern that although desirable genes can quickly be introduced into the herd or flock, there is also the potential to rapidly introduce undesirable genes. These may lead to an increased risk of genetic abnormalities, susceptibility to disease and other welfare consequences, according to the report.
The FWAC report recommends that breeding records of animals produced by cloning will need to be kept for several generations and that this may require new legislation.
CLONING RESEARCH
• Copying superior animals.
• Heavy losses in pregnancy.
• Must control inbreeding.