Traditional Selection for Fertility
University of Nebraska Extension beef genetics specialist Matt Spangler.
DES MOINES, Iowa (Sept. 8, 2016) — Call it a reprimand, an admonishment or a verbal spanking, but, by his own admission, Matt Spangler wanted to stir discomfort. The University of Nebraska Extension beef genetics specialist challenged the thought processes of cow-calf folk attending the Applied Reproductive Strategies in Beef Cattle conference hosted Sept. 7-8 in Des Moines, Iowa. Calling results achieved through “traditional” genetic selection tools and methods for improving beef cattle reproductive traits “poor, at best,” Spangler lamented the fact that other available and effective tools and methods are not well used.
Reminding the audience of the economic importance of reproduction, Spangler said traits associated with female fertility are twice as important to the average cow-calf enterprise as growth traits and 10 times as important as traits associated with carcass merit. Unfortunately, the number of expected progeny differences (EPDs) that currently exists for female fertility traits is limited, particular compared to the number of EPDs for growth and carcass merit.
Noting that antagonisms can exist between fertility and the other economically relevant traits, Spangler said selection for maternal and terminal characteristics, simultaneously, often is frustrating. Because of the number of EPDs now available for individual traits, he questions whether producers can effectively use all of them. Spangler said multiple-trait selection tools can account for antagonisms and provide for comparison of animals’ genetic potential for profit, based on a producer’s breeding objective. However, Spangler believes each producer must delineate a breeding objective as having either a maternal or terminal focus.
Spangler said he strongly advocates three action items that would, in his opinion, lead to improved reproductive performance. First, he recommended that the commercial cow-calf industry utilize composite or F1 females in pursuit of a terminal objective. They would use sires selected for early growth rate, calving ease direct, calf survival, disease susceptibility, feed intake, meat quality and carcass composition. No replacement females would be retained. Small operations in particular would benefit from purchasing replacement females, either bred heifers or bred cows but the latter would be preferred.
“Especially for small operations, managing heifers as a separate group can be cumbersome,” said Spangler. “It seems logical that they could simplify management and increase profitability by purchasing replacement females. Their cows could then be bred to terminal sires and all calves could be sold.”
In Spangler’s opinion, a maternal objective might be best suited to large commercial cow-calf and seedstock ranches that take advantage of scale to serve as multipliers, raising and marketing F1 or composite replacement females selected for fertility, maternal calving ease, longevity, moderate size, adaptation to production environment, disease susceptibility, optimal milk production, maternal instinct, and temperament. It’s likely that sexed semen could play a valuable role in producing females that ultimately would be marketed to small- and medium-sized operations.
As a second action point, Spangler called for advancement of the genetic evaluation of fertility/reproduction past the current metrics evaluated in National Cattle Evaluation. He noted that only heifer pregnancy and stayability are evaluated in the United States, while other countries include other reproductive traits such as days to calving, calving interval and bull scrotal circumference. As a tangible starting place, Spangler recommended a bivariate model jointly evaluating heifer pregnancy (early fertility) and days to calving (sustained reproduction).
Thirdly, Spangler called for action to effectively apply economic selection indices in the development of maternal and terminal selection lines.
Spangler said the actions described would offer more cost-effective benefits than genomic selection tools, given the current state of phenotypic data collection and breeding program design in the U.S. beef industry.
“This is not to say that genomics cannot, and will not, play an important role,” allowed Spangler, “but if producers have not taken advantage of the low-hanging fruit, any advantage from genomics (relative to improved fertility) will be marginal.”
Spangler spoke during Thursday’s ARSBC session focusing on genetics. Visit the Newsroom at www.appliedreprostrategies.com, which features comprehensive coverage of the symposium, to view his PowerPoint, read the proceedings or listen to the presentation. Compiled by the Angus Media editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.
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