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Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings Publication Acceptance Date: 8/19/2002 Publication Date: N/A Citation: N/A Interpretive Summary: The selection indexes computed by dairy cattle breeders have improved greatly in recent decades. Current indexes in 12 countries with the most Holstein cows indicate that protein yield has highest emphasis but that many other traits also are important. Longevity receives from 6 to 15% of total emphasis in nearly all countries. Most breeders also select for reduced somatic cell count or mastitis and a variety of conformation traits. Improved fertility, calving ease, temperament, and milking speed also are included in the indexes of three or more countries. International evaluations are needed for more of these traits so that foreign and domestic bulls can be compared fairly. The methods used to derive the Net Merit index introduced by USDA in August 2000 are presented as an example of selection for lifetime profit. The use of a profit function allows breeders to select for many traits by combining their incomes and expenses into an accurate measure of overall profit. Technical Abstract: The selection indexes computed by dairy cattle breeders have improved greatly in recent decades. Current indexes in 12 countries with the most Holstein cows indicate that protein yield has highest emphasis but that many other traits also are important. Longevity receives from 6 to 15% of total emphasis in nearly all countries. Most breeders also select for reduced somatic cell count or mastitis and a variety of conformation traits. Improved fertility, calving ease, temperament, and milking speed also are included in the indexes of three or more countries. International evaluations are needed for more of these traits so that foreign and domestic bulls can be compared fairly. The methods used to derive the Net Merit index introduced by USDA in August 2000 are presented as an example of selection for lifetime profit. The use of a profit function allows breeders to select for many traits by combining their incomes and expenses into an accurate measure of overall profit. |
