Who Got the Job Done?
DNA testing can help determine performance, economic value of bulls in a multi-sire breeding pasture.
SIOUX FALLS, S.D. (Dec. 3, 2012) — According to geneticist Alison Van Eenennaam, the number of progeny produced by a given natural-service sire likely is the most dominant factor influencing ranch income. That was one take-home message shared during the University of California–Davis researcher’s presentation to the Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium Dec. 3-4 in Sioux Falls, S.D. Based on results of a study led by Van Eenennaam, the ability to predict sire prolificacy would offer ranchers a significant economic advantage.
"What we'd like to see is bulls getting a large number of cows pregnant early in the breeding season. The data suggest 72% of ranch income comes from calves born during the first 42 days of the calving season,” said Van Eenennaam.
Toward that end, it appears, some bulls can and will do their part. Other bulls can’t do it, or maybe they just don’t try.
Van Eenennaam described the California Commercial Ranch Project, which evaluated nine calf crops from three different ranching operations using primarily Angus bulls in multi-sire breeding pastures. DNA paternity testing was applied to the roughly 6,000 calves evaluated.
Results indicated bulls sired from 0 to 54 progeny per calving season, Van Eenennaam shared. Even though all bulls had passed breeding soundness examinations (sometimes referred to as BSEs) prior to the breeding season, some bulls sired no calves. At the other extreme were the superstars.
The wide range of bull prolificacy resulted in large differences in the bulls' contribution to total ranch income, whether calves were sold as feeder cattle or ownership was retained until harvest. However, some bulls sired calves that were more profitable when marketed as feeders, while progeny of other bulls were more profitable when ownership was retained.
Noting that scrotal circumference has previously been linked to fertility traits in males and females, Van Eenennaam said the study results suggest size also matters to sire prolificacy.
"We saw a positive correlation for increased prolificacy with scrotal circumference EPD (expected progeny difference). I don't want to overstate it, but at least 5% of total variation (in prolificacy) was explained by scrotal circumference. Cow Energy Value Index ($EN) also was positively correlated, explaining about 3% of the variation," said Van Eenennaam, adding that milk and carcass weight EPDs were negatively correlated.
Based on market prices at the time of analysis, according to Van Eenennaam, the research suggests that each unit increase (1 cm) in scrotal EPD would be associated with 8.2 more progeny, and in excess of $7,000 more ranch revenue, per sire, when calves are marketed as feeder cattle or when ownership is retained. Each unit increase in $EN index would be associated with 0.45 more progeny and a little more than $350 more income, per sire. Income estimates are based on cattle prices at the time study results were analyzed.
"Collectively," concluded Van Eenennaam, "this suggests scrotal circumference EPD, and possibly $EN, should be included in bull selection decisions to increase prolificacy and total income under natural-breeding systems similar to these ranches."
Van Eenennaam spoke during Monday's ARSBC session focused on genetics. Visit the Newsroom at www.appliedreprostrategies.com to listen to her presentation at to view the accompanying PowerPoint slides and proceedings paper.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproductive Task Force and LiveAuctions.tv.
Editor's Note: This article was written under contract or by staff of the Angus Journal. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.