Genetic Selection for Fertility, Performance
FORT COLLINS (Dec. 3, 2008) — Beef cattle breeders seeking to enhance profitability through genetic improvement should focus on economically relevant traits, advised Colorado State University geneticist Denny Crews during the Robert E. Taylor Memorial Symposium in Fort Collins, Colo. Crews said traits related to fertility and maternal productivity definitely are economically relevant and typically have greater impact on profitability than traits related to growth and carcass merit.
“Make sure genetic selection decisions are based on economically relevant traits and not directly on an indicator,” advised Colorado State University geneticist Denny Crews.
Crews said few large-scale genetic evaluations for fertility traits have been implemented. Rather, economically relevant traits (ERTs), such as heifer pregnancy and cow stayability (productive longevity), have largely been relegated to evaluation and selection for easily measured indicator traits. These are traits that are genetically correlated with ERTs, but are not themselves economically important.
For example, Crews said, scrotal circumference in yearling bulls serves as an indicator trait, since it is known to be favorably correlated with bull fertility and age of puberty in related females. Its heritability is relatively high. The drawback is that it is also highly correlated with growth rate. And an increased growth response to selection for increased scrotal circumference may not complement selection goals for increased fertility.
“We need a novel approach to uncouple scrotal circumference from the growth component,” Crews said. “An alternative measure of scrotal circumference more closely describing its indication of genetic merit for fertility is needed.”
Systems for better genetic evaluation of fertility-related ERTs are being pursued, with the goal of predicting expected progeny differences (EPDs) with increased accuracy. Crews said the combination of multiple-trait approaches to modeling, increasing accuracy with indictor traits and the potential of marker-assisted selection should aid selection for beef cattle fertility.
If they gained nothing else from his presentation, Crews urged symposium attendees to remember the distinction between economically relevant traits and indicator traits.
“Make sure genetic selection decisions are based on economically relevant traits and not directly on an indicator,” Crews warned. “The best selection for an economically relevant trait is based on a model involving multiple indicators.”
The Robert E. Taylor Memorial Symposium is conducted by Colorado State University every other year to provide current, research-based information for improving profitability in the beef cattle industry. The ARSBC program was developed by the Beef Cattle Reproduction Task Force to improve understanding and application of reproductive technologies, including AI, estrus synchronization and factors affecting male fertility. In 2008, CSU and the Task Force collaborated to provide the Dec. 2-3 symposium in Fort Collins. To listen to Crews’ presentation, view the accompanying PowerPoint or view other presentations from the symposium, visit the newsroom at www.appliedreprostrategies.com.
— by Troy Smith
Editor’s Note: This article is available as a news release to redistribute per an agreement between the symposium hosts and Angus Productions Inc. Click here to submit a request for a high-resolution photo of the speaker. For additional information visit the newsroom of www.appliedreprostrategies.com.