National Dairy Genetic Index Update, Base Change Set for April 2025
Written by CDCB
December 20, 2024
Two significant updates will be implemented in the April 2025 dairy genetic evaluations published by the Council on Dairy Cattle Breeding (CDCB) – a revision to the lifetime merit indices and a genetic base change. The CDCB Board of Directors approved these revisions at their December 18, 2024 meeting.
On April 1, 2025, dairy producers will receive genetic evaluations for Lifetime Net Merit $ (NM$), Lifetime Cheese Merit $ (CM$), Lifetime Fluid Merit $ (FM$), and Lifetime Grazing Merit $ (GM$) built on new economic weights and an updated genetic base. The lifetime merit indices promote a balance of traits to maximize dairy cow profitability. These CDCB indices – produced in partnership with USDA-ARS Animal Genomics and Improvement Laboratory – estimate the difference in lifetime profit that each animal is expected to transmit to its progeny, expressed in U.S. dollars.
As the primary genetic selection index in the U.S., Net Merit $ ranks dairy animals on their combined genetic merit for nearly 40 economically important traits. All animals who receive a genetic evaluation from CDCB, the national genetic evaluation center in the U.S., receive merit index values alongside genetic evaluations for 49 individual selection traits and composites based on tens of millions of records stored in the National Cooperator Database.
The lifetime merit indices are updated periodically to reflect new traits, new research and current dairy market data. The April 2025 revision includes adjustments to the weights placed on individual traits and composite indices due to changes in the economic values of traits. Most notable is the enhanced commitment to dairy cattle genetic improvement and profitability through feed efficiency, component-based milk pricing, and fertility. The following table shows the expected relative value of economically rooted weights of traits in the revised April 2025 Net Merit $ formula, compared to weights in the current formula. Calculations show a 0.992 correlation, indicating little reranking expected of most animals.
| Trait Name | Current (August 2021) | April 2025 | Change |
| Milk | 0.3 | 3.2 | 2.9 |
| Fat | 28.6 | 31.8 | 3.2 |
| Protein | 19.6 | 13 | ¯ 6.6 |
| Somatic Cell Score | -2.8 | -2.6 | ¯ 0.2 |
| Productive Life | 15.9 | 13 | ¯ 2.9 |
| Livability | 4.4 | 5.9 | 1.5 |
| Heifer Livability | 0.5 | 0.8 | 0.3 |
| Health $ | 1.4 | 1.5 | 0.1 |
| Udder Composite $ | 3.4 | 1.3 | ¯ 2.1 |
| Body Weight Composite $ | -9.4 | -11 | 1.6 |
| Foot and Leg Composite $ | 0.4 | 0.4 | ¾ |
| Calving Ability $ | 2.9 | 3.3 | 1.4 |
| Daughter Pregnancy Rate | 4.1 | 2.1 | ¯ 2.0 |
| Cow Conception Rate | 1.0 | 1.8 | 0.8 |
| Heifer Conception Rate | 0.4 | 0.5 | 0.1 |
| Early First Calving | 1.2 | 1 | ¯ 0.2 |
| Residual Feed Intake | -4.8 | -6.8 | 2.0 |
Additional information on the lifetime merit indices update will be shared with industry organizations and dairy producers in early 2025 at uscdcb.com and through the CDCB Connection e-newsletter. A technical document from USDA-AGIL will be available in early January.
Genetic Base Change in April
These merit index values, along with the 49 individual selection traits and composites produced by CDCB, will be expressed on an updated genetic base relative to dairy cows born in 2020. In the U.S., this update occurs every five years to best align selection tools with the current dairy herd. Final base change values will be shared with the April 2025 evaluation release. As producers define breeding strategies for 2025, they can expect changes in predicted transmitting ability (PTA) values similar to these preliminary estimations.
| Trait Name | Units | Brown Swiss | Holstein | Jersey |
| Milk | Pounds | 350 | 750 | 400 |
| Fat | Pounds | 10 | 45 | 20 |
| Protein | Pounds | 15 | 30 | 15 |
| Somatic Cell Score | Log base 2 units | 0 | -0.1 | 0 |
| Productive Life | Months | 1 | 2.5 | 1.5 |
| Livability | % | 0.5 | 0.5 | 0.5 |
| Mastitis | % | -0.2 | 0.75 | -1 |
| Daughter Pregnancy Rate | % | -0.6 | -0.2 | -0.4 |
| Cow Conception Rate | % | -0.5 | 0.5 | 0 |
| Heifer Conception Rate | % | 0.1 | 1 | 1.5 |
| Early First Calving | Days | 0.5 | 2 | 2 |
| Residual Feed Intake | Pounds | – | -40 | – |
| Final Score | 0.2 | 0.6* | 0.6 |
*Holstein type traits are calculated by Holstein Association USA. This estimation was provided by HAUSA. Holstein Final Score was updated in this table on 1/3/2024, as the number in the original post was inverted.
Since 2013, the Council on Dairy Cattle Breeding has been responsible for publishing genetic evaluations, stewarding the National Cooperator Database, and providing national dairy performance benchmarks. CDCB works in conjunction with the USDA-ARS Animal Genomics and Improvement Laboratory to research new genetic methodologies, selection traits, and tools for reporting genetic conditions.