two or three years grows to an ox. The female is first a heifer calf, growing into a heifer and becoming a cow. Dairy cattle are those breeds that have been developed primarily to produce milk. The achievements of careful breeding have been outstanding because the individual high-performance cows could produce more than four times the average amount of milk and butterfat. In North America the major breeds of dairy cattle are the Holstein-Friesian, Brown Swiss, Ayrshire, Guernsey, and Jersey. The ancestors of these animals were import
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