What are Herd Bulls Accomplishing in
Multiple-Sire Breeding Pastures?
JOPLIN, Mo. (Sept. 1, 2011) — Outside of paternity testing, there is no way to know which calves were sired by individuals in a multi-sire pasture. Using DNA testing to accomplish that, a recent study of progeny from 2,400 cows bred to 100 bulls on three California ranches showed a range of 0 to 54 calves per bull used.
Using DNA testing to know which calves were sired by individuals in a multi-sire pasture showed a range of 0 to 54 calves per bull used, said Alison Van Eenennaam, University of California-Davis animal scientist.
Alison Van Eenennaam, University of California-Davis animal scientist, shared results and implications Thursday, Sept. 1, at the Applied Reproductive Strategies in Beef Cattle (ARSBC) meeting in Joplin, Mo.
“We saw huge variations in production and dollar returns,” she said. “This bull produced 20,000 pounds of weaning weight, this one 1,000 pounds; 7.3% of them failed completely and did not sire any calves.”
While that was interesting, Van Eenennaam noted follow-up studies looked at repeatability in those production patterns. “We found it is moderately repeatable, at 0.33,” she reported. Similarly, by sampling DNA of dead calves, those problems were found to be moderately repeatable by sire.
However, cost of testing was a major barrier to culling bulls by DNA results. “You could justify finding and culling the 7% nonbreeding bulls if DNA testing only cost $1 per head,” she said, but even at $5 per head, it would not pay unless 25% of the bulls were to be culled and replaced with better ones.
The studies underscored common knowledge that senior bulls prevent younger bulls from breeding, even if the young bulls are much more capable. Although many producers introduce yearling bulls into a battery of older ones, Van Eenennaam said that practice should end: “Keep the yearlings together in a pasture.”
In the California pastures, she said ranchers were buying “single-trait-selected calving-ease bulls” and then using them on older cows when they grew to mature weight. “A better plan would be to use high-accuracy calving-ease sires on heifers using artificial insemination (AI),” she added.
Van Eenennaam spoke during Thursday's ARSBC session focused on reproductive considerations related to the male. Visit the Newsroom at www.appliedreprostrategies.com to view the PowerPoint slides and proceedings paper submitted by Van Eenennaam to accompany her presentation. Audio of the presentation will be available soon.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by Angus Productions Inc. (API), the site is made possible through sponsorship by the Beef Reproductive Task Force, SEK Genetics, and liveauctions.tv. Coverage includes summaries of the speaker presentations, PowerPoints, proceedings and audio.
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