2002 Across Breed EPD Adjustments
Livestock Update, August 2002
Scott Greiner, Extension Animal Scientist, Beef, VA Tech
The table of adjustment factors to estimate across-breed expected progeny differences for various beef cattle breeds was released at the Beef Improvement Federation Annual Meeting in San Antonio, Texas on July 19. By using the across breed adjustment factors, animals of different breeds can be compared on the same EPD scale. The adjustment factors are based on comparative studies of the breeds conducted at the U.S. Meat Animal Research Center in Clay Center, Nebraska and adjusted to a year 2000 base using EPDs from the most recent national cattle evaluations.
To calculate across breed EPDs, simply add the adjustment factor found in the table to the within-breed EPD calculated in the most recent genetic evaluation for the animals of interest. For example, consider a Simmental bull with a WW EPD of +35 and a Charolais bull with WW EPD of +15. Would we expect the progeny out of different breed of dam for these two bulls to weigh about the same? To fairly compare the WW EPDs of these two bulls of different breeds, the EPDs must first be adjusted using the across-breed table. Using the table, the Simmental bull would have an across-breed WW EPD of +56.5 (35 + 21.5 = 56.5) and the Charolais bull an across-breed WW EPD of +54.0 (15 + 39.0 = 54.0). In this example, we would expect progeny of the Simmental bull and Charolais bull to be very similar on the average for weaning weight (across breeds EPDs of 56.5 vs. 54.0, for only a two pound difference) when mated to cows of a different breed.
The adjustment factors may also be useful in managing uniformity when breeds are rotated in a crossbreeding system to avoid large fluctuations in traits such as birth weight and milk. For example, using these adjustments, it can be demonstrated that a Gelbvieh bull with a milk EPD of +10 will add similar milk genetics when compared with an Angus bull with a milk EPD of +20 (both the bulls would be +20 on an across-breed basis). This demonstrates the differences between the breeds that exist- as a Gelbvieh bull with a +10 milk EPD ranks in the lower 5% of the Gelbvieh breed for milk genetics, whereas the Angus bull with a milk EPD of +20 ranks in the top 30% of the breed. With this in mind, a Gelbvieh bull can be selected to compliment an Angus cow base that will add a moderate amount of milk. Similar calculations can be made for birth weight and growth. The key is to recognize the basic genetic differences between breeds, and then select of bulls within those breeds with optimum genetics while avoiding extremes.
|2002 Adjustment Factors to Add to EPDs of Various Breeds to Estimate Across-Breed EPDs|
|Breed||Birth wt.||Weaning wt.||Yearling wt.||Milk|