Beef Improvement Federation: New Growth Metric Could Improve Beef-on-Dairy Genetic Evaluations

Researchers aim to boost accuracy of National Cattle Evaluation with earlier-in-life weights.

AMARILLO, Texas — Incorporating earlier-in-life growth metrics into the National Cattle Evaluation could strengthen genetic predictions for beef-on-dairy cattle, according to Ryan Boldt, Ph.D., lead geneticist for International Genetic Solutions (IGS).

Boldt said that a research project he’s part of builds on earlier work that integrated beef-on-dairy records into evaluations for carcass traits. By capturing more phenotypes from crossbred calves, researchers hope to refine selection tools, improve indexing and provide producers with better insight into growth performance at multiple stages of an animal’s life.

More Carcass Data Paves the Way

Previous efforts to include beef-on-dairy data in the national evaluation have yielded significant benefits for carcass trait records. Historically, carcass data represented only 1 to 2 percent of animals in the evaluation. With the addition of beef-on-dairy phenotypes, that share has risen to 12 to 15 percent for recent birth years.

The increase parallels the growth in genomic data over the same period. High genetic correlations between beef-on-dairy and native beef animals for carcass traits have allowed these phenotypes to be analyzed as the same trait and ensures that data from one system benefits the other.

This expansion has also had spill-over effects across breed associations. While all beef-on-dairy data currently comes through a single association, sire relationships connect across multiple databases to spread the benefit of additional records throughout the IGS system.

Shifting Focus to Early Growth

Building on carcass trait integration, the project examines earlier-in-life weights, particularly a feedlot entry weight collected at around 140 days of age. Researchers wanted to determine if such measurements could be included alongside traditional growth traits—birth weight, weaning weight and post-weaning gain—in the national evaluation.

The study compared data from two streams: native beef animals (beef-on-beef) and beef-on-dairy calves. For birth weight and post-weaning gain, high genetic correlations (0.89 and 0.91, respectively) suggested that these traits could be analyzed jointly across both groups.

Weaning weight was more complex. While heritability estimates were higher than traditional literature values, the genetic correlation between beef-on-beef weaning weight and beef-on-dairy adjusted 205-day weight was lower at 0.65, prompting further investigation.

Refining the Beef-on-Dairy Weight

Researchers discovered that the average age at feedlot entry for beef-on-dairy animals was about 140 days, with most weights collected between 100 and 160 days of age. When these weights were adjusted to 205 days using the standard nonlinear function for native beef, the fit was poor.

A linear adjustment, by contrast, matched the beef-on-dairy data more closely, with a strong relationship (R² = 0.94) between age and weight. This finding prompted a shift in strategy: rather than forcing these weights into a 205-day framework, the 140-day feedlot entry weight would be treated as its own trait in the evaluation.

Distinct Relationships and Genetic Links

When modeled as a 140-day weight, the genetic correlation with native beef weaning weight dropped to 0.41, suggesting that while related, the two traits capture different biological information.

An unexpected finding was the weaker-than-anticipated correlation between birth weight and early growth in beef-on-dairy calves compared to native beef animals. This may reflect

differences in management systems, given that beef-on-dairy calves are not raised by their dams and follow a unique production path from birth through feedlot entry.

Despite these differences, heritability estimates for the 140-day weight and other traits fell in line with typical expectations when maternal effects for native beef weaning weight were included.

Implementation Plans

Based on the results, the proposed approach is to maintain the traditional growth analysis—including birth weight, weaning weight, post-weaning gain and weaning weight maternal—while adding a separate trait for the beef-on-dairy 140-day adjusted weight.

This new metric is expected to be especially valuable for beef-on-dairy indexing and will help associations design tools that account for growth differences at specific time points. While it may not offer much benefit for traditional beef-on-beef programs, the data could improve predictions for systems relying heavily on beef-on-dairy production.

Notably, 140-day weights will not factor into weaning weight maternal EPD calculations, since beef-on-dairy calves are raised in artificial rearing systems rather than by their dams.

Broader Benefits of Beef-on-Dairy Data

The integration of beef-on-dairy data continues to deliver advantages beyond its own sector. High-use AI sires in dairy herds generate large numbers of progeny records, which boosts the accuracy of EPDs for both carcass and growth traits.

In some carcass weight analyses, dairy breeds rank third and fourth in the number of sires with high-accuracy EPDs. This is a testament to the power of these connected data streams. Distributions of EPDs for Holstein and Jersey sires often match or exceed those of beef breeds in certain traits, underscoring their genetic diversity and potential for targeted selection.

Looking Ahead

With implementation underway, researchers expect the addition of the 140-day weight to enhance the precision of beef-on-dairy genetic evaluations. By leveraging the strong genetic correlations where they exist and accounting for differences where they don’t, IGS aims to maximize the utility of every available data point.

“As we continue to expand the number of phenotypes and records from this valuable data stream, it’s critical to incorporate them in ways that improve accuracy for both beef-on-dairy and native beef predictions,” Boldt said.

The project reflects a broader shift in cattle breeding: embracing new metrics and production realities while ensuring that genetic tools remain relevant across diverse management systems.

Takeaways

· Beef-on-dairy data boosts evaluation accuracy – Incorporating beef-on-dairy records, especially carcass traits, has significantly increased phenotypic data in the National Cattle Evaluation, which benefits multiple breed associations.

· 140-day weight offers a new growth metric – Feedlot entry weight at about 140 days is a distinct, heritable trait for beef-on-dairy calves to be added separately to growth evaluations instead of adjusting to 205 days.

· High genetic correlations for some traits – Birth weight and post-weaning gain in beef-on-dairy and native beef animals are closely related, and therefore, allow for joint analysis. Weaning weight shows weaker genetic links.

· Management differences shape results – Beef-on-dairy calves’ unique production system, including artificial rearing, influences growth patterns and reduces correlations seen in traditional beef cattle.

· Broader industry benefits – Data from high-use AI dairy sires enhances EPD accuracy across the IGS network, with some dairy breeds showing competitive or superior genetic diversity in certain traits.

–Beef Improvement Federation