USDA Publishes Revised
Overall Merit Values
The U.S. Department of Agriculture has revised the formulas used to calculate Net Merit Dollars (NM$), Fluid Merit Dollars (FM$) and Cheese Merit Dollars (CM$) to include cow fertility and calving ease, effective August 2003. University researchers developed the new indexes with input from industry. The revisions are part of the ongoing process of developing selection tools that more accurately reflect the economic realities on U.S. dairy farms.
The new formulas incorporate genetic evaluations for daughter pregnancy rate (DPR), service-sire calving ease (SCE) and daughter calving ease (DCE). The intent is to incorporate these traits so that tools are available to help select animals that have an appropriate balance between production and reproduction. The formula reduces emphasis on PTAs for milk, protein and productive life to make room for adding these new traits (see table 1). Also, the USDA Merit formulas will be different for Holsteins than for the high-components breeds, because calving-ease evaluations are calculated only for Holsteins. These differences are shown in the table as well.
Table 1. Weights assigned to various components of the formula to calculate Net Merit Dollars, August 2003.
| Trait |
Previous NM$
All Breeds |
New NM$
Holsteins |
New NM$
High-Components Breeds |
| Milk |
5% |
0% |
0% |
| Fat |
21% |
22% |
23% |
| Protein |
36% |
33% |
35% |
| Productive Life |
14% |
11% |
11% |
| Somatic Cell Score |
-9% |
-9% |
-10% |
| Udder Composite |
7% |
7% |
7% |
| Feet-and-Leg Composite |
4% |
4% |
4% |
| Body-Size Composite |
-4% |
-3% |
-3% |
| Daughter Preg. Rate |
0% |
7% |
7% |
| Service-Sire Calv. Ease |
0% |
-2% |
0% |
| Daughter Calving Ease |
0% |
-2% |
0% |
The new formulas will cause A.I. sires to rank differently. Bulls that transmit improved fat and protein percents as well as those bulls with high DPR and low calving ease will rank better for NM$ with the new formula. In Table 2 you’ll find a few examples of Select sires and the changes in their NM$ values due to the formula changes.
Table 2. Changes in NM$ values of six sires.
| Sire |
Previous NM$
May 2003 |
New NM$
May 2003 |
Difference |
| 7HO6417 O MAN*TV |
759 |
810 |
+51 |
| 7HO6349 BEST*TV |
533 |
567 |
+34 |
| 9HO2538 GEARR*TV |
530 |
496 |
-34 |
| 7HO6042 SIR *TV |
523 |
476 |
-47 |
| 7HO5157 DURHAM*CV |
385 |
432 |
+47 |
| 7HO5708 BLITZ*TV |
326 |
289 |
-37 |
The emphasis these traits receive in the formula are useful, but, because of the different heritabilities and genetic relationships between these traits, it is difficult to know how much change actually will be made in the resulting cows. USDA calculated the theoretical genetic changes that can be expected when using the new formulas. Its results show that genetic improvement for the production traits will be 10 percent less. But, by sacrificing some improvement in production, additional improvement can be achieved for all other traits included in the formula. Increased improvement will be fairly significant for productive life, Somatic Cell Score (SCS) and the calving-ease traits.
In theory, the revisions to the USDA Merit formulas make a lot of sense. However, a little bit of caution is advised. Adding the lowly heritable traits of DPR and DCE will reduce the overall reliability of the Merit values. Most A.I. sires have low reliabilities for these traits. Also, DPR genetic evaluations are fairly new and the jury is still out as to whether these values indicate true genetic differences in fertility.
It’s obvious that dairy producers have more interest than ever in improving reproduction. The new Merit formulas are currently the best routinely available tools for producers who have decided to use PTAs for DPR when selecting sires. Using NM$, CM$ or FM$ for sire selection will be much more effective than a selection program that requires all bulls to be above a certain minimum DPR value. We are still new at computing genetic evaluations for reproductive traits, and it is likely these formulas will be revised in the future as we learn more about evaluating these traits.
Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751
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