Submitted to: Infortambo
Publication Type: Trade Journal
Publication Acceptance Date: 6/1/2000
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: During 2000, the United States and many other countries will be updating their genetic bases for dairy cattle evaluations. A genetic base is a reference point from which genetic merit is expressed. Typically, a group of animals in a given year is selected, and the average of their evaluations is set to zero. The U.S. genetic base for the past 5 years has been defined as the average predicted transmitting ability (PTA) of cows that were born in 1990. Genetic bases often are updated periodically to reflect genetic progress. Current U.S. production trends indicate that PTA's for Holstein cows are increasing by about 135 pounds of milk each year, and that rate generally has been increasing over the last 35 years. If only the genetic base were changed in August 2000, decreases in U.S. evaluations would be the amount of PTA progress for cows born in 1995 relative to 1990: 675 pounds of milk, 20 pounds of fat, and 20 pounds of protein. However, because of other changes to the U.S. genetic evaluation system, those decreases will not be uniform for all animals. A stepwise base with updates every 5 years is the international standard that is recommended by the International Bull Evaluation Service (Interbull). Interbull combines national evaluations from many countries and expresses the resulting combined evaluations on each national scale so that evaluations from different genetic bases can be compared. Because Interbull evaluation procedures account for different genetic bases from different countries, breeders in any country do not need to adjust evaluations or question if they are comparable as long as comparisons among bulls are made using the most recent Interbull evaluations on one country's scale.