Author
|
Submitted to: AIPL Research Reports
Publication Type: Government Publication Publication Acceptance Date: 11/8/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Selection of animals to be parents of the next generation of U.S. dairy cattle should be more accurate if all traits of economic value are included in the net merit (NM$) index that is calculated by USDA. Previously, conformation traits affected NM$ of Holstein bulls only through relationships with productive life. For bulls and cows of other breeds and for Holstein cows, conformation traits were not included in NM$. Beginning in August 2000, NM$ became a lifetime profit function that uses actual incomes and expenses as proposed and developed through Project S-284, Genetic Enhancement of Health and Survival for Dairy Cattle, a collaborative research effort of the Southern Association of Agricultural Experiment Station Directors. Two other lifetime merit indexes (fluid merit and cheese merit) also were developed based on fluid milk and cheese market pricing instead of standard milk-fat-protein pricing. All three indexes combine the economic values of an animal's genetic merit for yield (milk, fat, and protein), longevity (productive life), mastitis resistance (somatic cell score), and conformation (udder, feet and legs, and body size composites). The profit function approach lets breeders select for many traits by combining the incomes and expenses for each trait into an accurate measure of overall profit. Producers should use the lifetime merit index that corresponds to the market pricing that they expect a few years in the future when buying breeding stock and 5 years in the future when buying semen. Technical Abstract: Selection of animals to be parents of the next generation of U.S. dairy cattle should be more accurate if all traits of economic value are included in the net merit (NM$) index. Previously, type traits affected NM$ of Holstein bulls only through correlations with productive life. For bulls and cows of other breeds and for Holstein cows, type traits were not included in NM$. Beginning in August 2000, NM$ became a lifetime profit function that uses actual incomes and expenses as proposed and developed through Project S-284, Genetic Enhancement of Health and Survival for Dairy Cattle. Incomes and expenses that repeat for each lactation are multiplied by the cow's expected number of lactations, which results in a nonlinear profit function based on an animal's genetic merit for yield (milk, fat, and protein), longevity (productive life), mastitis resistance (somatic cell score), and conformation (udder, feet and legs, and body size composites) through the combination of three subindexes: Yield$, Udder$, and Other$. Two other lifetime merit indexes (fluid merit and cheese merit) also were developed based on fluid milk and cheese market pricing instead of standard milk-fat-protein pricing. A linear approximation of the nonlinear function is used to calculate the official values for the three lifetime merit indexes. The profit function approach lets breeders select for many traits by combining the incomes and expenses for each trait into an accurate measure of overall profit. Producers should use the lifetime merit index that corresponds to the market pricing that they expect a few years in the future when buying breeding stock and 5 years in the future when buying semen. |
