17 October 1996 Identical twin lamb breakthrough a research cost­ saver

It was a special spring for Lincoln animal scientists this year as they watched with delight the birth of an unusually high number of twins among Coopworth flock on the University's Research Farm.

Well-known in general for their high fertility and mothering ability, the Coopworths at Lincoln this season provided confirmation of work Dr Graham Kay, Nigel Jay and Dennis Herrick of the Animal and Veterinary Sciences Group have been doing to simplify established techniques for ensuring the production of genetically identical animals.

Identical twins are extremely valuable in animal research as one of a pair can act as the "control" for the other. It reduces the number of animals required in studies and thereby reduces research costs.

Two of the sheep production programmes at Lincoln – one on immunity to parasites, the other on mineral metabolism programmes (and both of which involve Coopworths) – are characterised by large genetic variation between animals, so require large numbers of stock to validate tests. A programme to develop identical twin sheep by embryo bisection is now beginning to pay dividends by providing a large number of the desired progeny.

The bisection of sheep embryos for the artificial production of genetically identical animals was first achieved in 1980 but over the past two years Lincoln has developed a simpler technique. Team member Nigel Jay says it has involved much "painstaking research and many disappointments" to bring previous work on reproductive physiology into a "successful package", but they have done it.

"Our success rate with identical twin births this spring suggests we may, at last, have the right recipe," he says.

"Even so, potential users are faced with considerable difficulty unless they are experienced both in sheep embryo transfer and the micro-manipulation of splitting embryos, which requires manual dexterity and practice. Attention to detail in the production of embryos and in the handling of the embryos outside the mother is required."

Embryo splitting is based on the fact that normal sheep embryos have sufficient cells for the development of more than one foetus. Therefore, sheep embryos can be split into viable halves.

In a procedure that takes less than two minutes, the microsurgical bisection of sheep embryos is conducted under a microscope with a fine microknife which is precisely controlled with a micromanipulator.

Ian Collins, Journalist, Lincoln University, Canterbury, New Zealand.