Two thousand twenty-five genetic base shifts are most substantial for the Holsteins. Calving traits delayed amid inbreeding surge – what it means for your herd’s future.

EXECUTIVE SUMMARY: The 2025 U.S. genetic base change reveals accelerated progress but new complexities, with Holsteins facing amplified inbreeding impacts on PTAs. While most traits now reflect 2020-born cows, calving trait updates remain delayed until August due to calculation anomalies. Breed-specific adjustments demand revised selection strategies, particularly for semen use decisions. Updated Lifetime Net Merit indices reflect shifting market realities, while enhanced reliability calculations improve non-Holstein-type evaluations. This reset demands immediate breeder action to maintain genetic momentum.

KEY TAKEAWAYS:

• Base Change Magnitude: The largest adjustment in years reflects a 5-year genetic leap, requiring recalibration of PTA benchmarks
• Calving Traits On Hold: Phenotypic calculation quirks delay updates until August 2025 despite other traits going live
• Holstein Inbreeding Effect: Rising inbreeding rates amplify PTA shifts, demanding revised selection thresholds
• Economic Index Overhaul: NM$ revisions align with current milk prices and feed costs, altering sire rankings
• Strategic Imperative: Breeders must reassess sexed/beef semen use criteria to capitalize on new genetic realities

The April 2025 U.S. genetic base change represents one of the most significant updates in recent years, reflecting unprecedented genetic progress in dairy cattle over the past five years. As the base shifts from cows born in 2015 to those born in 2020, dairy producers will need to recalibrate their genetic selection strategies. The final values reveal substantial changes across breeds, with adjustments to PTA values, breeding indices, and reference populations. Notably, calving traits have been temporarily excluded due to unexpected results when applying the base change calculations, with updates for these traits postponed until August 2025 following further investigation. The accelerated genetic progress demonstrated by this base change, combined with increasing inbreeding rates, especially in Holsteins, signals both positive advancement and new challenges for dairy breeders.

Table 1: Value of the genetic change between cows born in 2020 and cows born in 2015.

– Trait not calculated and published for the breed
* Trait calculated by Holstein Association USA
** Economic weights applied to Lifetime Merit Indices are also updated in April 2025.

Understanding the Genetic Base Change Process

The U.S. genetic base update is a routine recalibration every five years to align selection tools with the current dairy herd’s genetic capabilities. Beginning April 1, 2025, the genetic evaluations produced by the Council on Dairy Cattle Breeding (CDCB) will shift their reference point from cows born in 2015 to those born in 2020. This shift resets the baseline against which all animals are measured, ensuring that genetic evaluations remain relevant in a rapidly improving population.

Every dairy animal with genetic evaluations based on CDCB and Holstein USA data is compared to this breed population average, known as the base. Traits are measured as Predicted Transmitting Abilities (PTAs) relative to this established baseline. As genetic progress continually advances, this five-year recalibration provides dairy producers with an accurate point of comparison, essentially serving as a genetic report card that demonstrates progress compared to the previous generation.

The 2025 base change is particularly notable because it’s larger than previous adjustments, directly reflecting the industry’s accelerated genetic progress in the preceding five years. Genomic evaluations and advanced reproductive technologies, including sexed semen, embryo transfer, and in-vitro fertilization, primarily drive this acceleration.

Key Adjustments and Their Implications

The genetic base change involves complex adjustments beyond measuring the genetic difference between cow populations from different years. After determining the genetic difference between cows born in 2020 and those born in 2015, inbreeding and heterosis adjustments are applied, significantly impacting the final PTA values.

In the Holstein breed particularly, the increasing rate of inbreeding over the five years has amplified the effect of these adjustments on PTA values. This means the numerical shifts in genetic evaluations reflect genetic advancement and changing population dynamics. Understanding these nuances is critical for correctly interpreting the new genetic evaluations for dairy producers.

Along with the base change, the Lifetime Net Merit (NM$) index is being revised, including updates to Cheese, Fluid, and Grazing Merit. This 2025 revision adjusts methods for estimating trait values and updates numerous income and cost variables, such as milk prices, feed requirements, and reproductive options. Such revisions ensure that selection indices reflect current economic realities and production objectives.

Breed-Specific Impacts

The magnitude of the base change adjustments varies considerably across breeds, reflecting different rates of genetic progress. These differential impacts underscore the importance of breed-specific genetic selection strategies. Dairy producers must adjust their selection thresholds accordingly, particularly when deciding which cows to breed with sexed semen versus beef semen.

Calving Traits: A Notable Exception

A significant aspect of the 2025 base change is the decision to maintain calving traits in their current base. The calving traits—Daughter Calving Ease, Sire Calving Ease, Daughter Stillbirth, and Sire Stillbirth—represent a unique category in which genetic evaluations are reported on an observed (phenotypic) scale, meaning both genetic and phenotypic bases must be updated during a base change.

Unexpected results emerged when these base updates were applied for the April evaluation. Due to the timing of this discovery, the CDCB decided to maintain calving traits using the same genetic and phenotypic bases used to calculate them in December 2024. This decision ensures reliability while allowing time for further investigation. The CDCB expects to update the bases for calving traits in August 2025 after completing a thorough analysis.

This temporary maintenance of the previous base for calving traits will not impact other characteristics in the genetic evaluations. New phenotypic data received since December will still be incorporated, ensuring the evaluations remain current despite using the previous base.

Updates to Reference Populations and Calculation Methods

Breed Base Representation Changes

In addition to the core base change, April 2025 brings significant updates to the Breed Base Representation (BBR) reference population. These updates implement refined business rules for selecting purebred bulls, made possible by increasing the availability of genotyped animals and advancements in data quality, methodologies, and technology.

The BBR reference population will now be selected from genotyped, progeny-tested bulls with at least 10 enrolled daughters (excluding bulls with status codes C and N), complete pedigrees, and are classified as purebred within each breed of evaluation. When rounded to the nearest integer, a purebred bull must have a pedigree-based heterosis value ≤ 1%.

These changes will affect the percentage of animals receiving new BBR values differently across breeds—from approximately 25% in Ayrshire to only about 1% in Holstein. Generally, the new methodology will decrease BBR values across breeds, as it improves the detection of animals with non-purebred ancestors.

Type Trait Reliability Calculations

For non-Holstein breeds, April 2025 brings a significant methodological update to type trait reliability calculations. Historically, while PTAs for type evaluations have been derived from a multiple-trait model, reliabilities were calculated using a single-trait model. The growing volume of appraisal data has prompted the alignment of both processes to follow the multiple-trait methodology.

As a result, traditional PTAs will remain unchanged. Still, reliabilities for most traits will increase, particularly those with limited data, which will now benefit from genetic correlations with other characteristics. Genomic PTAs will see more noticeable impacts as reliability adjustments affect SNP solutions and weighting factors in final calculations.

Strategic Implications for Dairy Producers

The 2025 base change presents dairy producers with a significant opportunity to reassess their genetic improvement strategies. With genetic progress accelerating, an effective selection strategy becomes increasingly crucial. Selection indices like Herd Health Profit Dollars® (HHP$®) provide efficient approaches to simultaneous improvement across multiple traits.

The adjustments coming in April mean producers will likely need to recalibrate their selection thresholds for A.I. sires and adjust criteria for determining which cows are bred to beef or sexed semen. This recalibration process is essential to maintain genetic progress and ensure that genetic selection decisions align with updated evaluations.

While potentially disruptive in the short term, the magnitude of this base change ultimately reflects the industry’s success in accelerating genetic improvement. It signals that dairy producers are making faster genetic progress than ever, necessitating corresponding evolution in genetic evaluation systems to maintain their accuracy and relevance.

Conclusion

The 2025 U.S. genetic base change represents both remarkable progress and an opportunity for strategic realignment. The substantial shifts in genetic evaluations across breeds demonstrate the dairy industry’s success in accelerating genetic improvement through advanced technologies and selection practices. While the adjustment process may temporarily disrupt established selection thresholds, it ultimately provides dairy producers with more accurate tools for genetic selection.

The special handling of calving traits highlights the complexity of genetic evaluation systems and the importance of maintaining evaluation integrity even when unexpected challenges arise. Meanwhile, the updates to reference populations and calculation methodologies further refine the precision of genetic evaluations.

This base change is a milestone for dairy producers, marking five years of genetic advancement and prompting them to reevaluate selection strategies to ensure continued progress. By understanding these changes and adjusting breeding decisions accordingly, producers can leverage this base change to enhance their herds’ genetic potential and profitability in the years ahead.

Read more:

• Genetic Revolution: How Record-Breaking Milk Components Are Reshaping Dairy’s Future
  Explores the 2025 component base adjustments driving butterfat/protein shifts across breeds, with Holstein fat PTAs dropping 45 lbs.
• Lactanet’s LPI April 2025 Update: What It Means for Dairy Farmers
  Details Canada’s parallel genetic evaluation overhaul introducing sustainability-focused subindexes and milking efficiency metrics.
• U.S. Dairy Genetic Evaluations Set for Historic Reset on April 2025
  Breaks down NM$ index revisions prioritizing feed efficiency and livability alongside PTA reductions across all significant breeds.

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