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Four Parents for Multi-Wool Sheep

While scientists at AgResearch Ruakura are celebrating the birth of a cloned calf -- an animal with only one genetic parent -- their associates at AgResearch Lincoln are working with chimaeric sheep, animals which have four parents each.

The 13 chimaeric sheep were born five years ago as part of a research project led by Dr David Scobie, and their unusual background has become more obvious now the sheep are mature.

"When the lambs were born we were uncertain whether or not they were true chimaeras as there were no obviously unusual features. However, as they aged it became apparent that some were growing two types of wool. Patches of short, fine, Merino wool could be found amongst the longer, coarser, Lincoln fleece."

Four Parents for Multi-Wool Sheep Figure A (22KB)

Each chimaeric sheep is the product of not one, but two naturally fertilised embryos, which are combined and then implanted into a surrogate mother. In this case, the combined embryos were from pure-bred Lincoln and Merino sheep, implanted into Coopworth ewes. Because the two eggs had been fertilised before they were combined, the resulting offspring were not Merino-Lincoln crosses, but individual animals with genes from four parents contributing to various organs and tissues. The animals carry two distinct types of wool and some of the Lincoln sheep also have Merino horns.

Scobie says the animals have no commercial value, but were specifically bred as research tools.

"No farmer wants sheep with two sorts of wool -- they would be a wool classer's nightmare! But for scientists they are an elegant research tool allowing us to research two different breeds of sheep using just one animal."

Scobie has used the chimaeric sheep in wool growth research involving sulphur amino acid supplements used to increase wool growth. The aim of the research was to discover if the increases would be the same in different sheep breeds. The supplements affected fibre length and diameter to the same extent in both the Lincoln and Merino wool.

This research could have been carried out on groups of pure Merinos and Lincolns, but Scobie says using the chimaeras had a number of advantages.

"Using different breeds would have required a large number of animals, and results could have been influenced by factors such as feed intake, digestion and circulating hormones. In chimaeric animals all such external variables and systematic factor effects are the same for the one animal, allowing any changes in growth of the two wool types to be interpreted more reliably. The sheep basically acted as life support systems for the two different populations of wool follicles. One chimaera can replace dozens of experimental animals of the original breeds."