In upgrading, foundation ewes of established breeds are chosen and artificially inseminated with the semen from the target breed (generation 1). The resulting ewe lambs, which carry about 50 percent target genetics, are in turn bred with imported semen, producing lambs that are about 75 percent target. By generation 7, the lambs are about 98 percent target. Upgrading never reaches 100 percent; there’s always some contribution of the foundation breed. As you can see, it requires six rounds of expensive artificial insemination to get to 98 percent and seven or eight years before that 98 percent crop of ewes is ready to be bred. Some breeds that have been or are being introduced to the United States this way include Teeswater, Wensleydale, Gotland, Kerry Hill, Zwartbles, Racka, and Herdwick.
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