Calf Performance Starts in the Womb
JOPLIN, Mo. (Sept. 1, 2011) — “Genetics don’t matter if you don’t manage them to their ability,” said Rick Funston a researcher at the University of Nebraska (NU) Central Research and Extension Center at North Platte, Neb.
"In a systems approach, we have to consider not only what we're doing to the cow, but also what we're doing to the calf," Rick Funston explained.
Funston wasn’t talking about increasing inputs to maximize outputs. He was telling participants at the Applied Reproductive Strategies for Beef Cattle (ARSBC) conference in Joplin, Mo., about the consequences on production from calves out of cows with restricted diets.
It has to do with something called fetal programming, how what the cow eats and what she endures during pregnancy impacts subsequent lifetime performance of the calf she’s carrying. Fetal programming is a growing area of study in both humans and livestock. Funston and his NU peers stumbled onto the effects of it with winter cow supplementation while researching year-round grazing in an effort to help ranchers reduce winter feeding costs.
“In a systems approach, we have to consider not only what we’re doing to the cow, but also what we’re doing to the calf,” Funston explained.
In one study — calves early-weaned in August or conventionally weaned in November, with cows receiving or not receiving winter supplementation — steer progeny from cows that weren’t supplemented ultimately gave up about 100 pounds (lb.) of live weight or about 60 lb. of carcass weight. Pregnancy rate of the cows was essentially the same between the study groups.
“In 11 years of studies we have seen no benefit of supplementing cows on winter range to her ability to breed or breed back,” Funston said.
A similar study that included spring supplementation via meadow grazing yielded similar results. When researchers followed heifer progeny, though, those from cows that received no supplementation had a 13% lower pregnancy rate than heifers from cows that had been supplemented. What’s more, 30% more of the heifers from supplemented dams conceived in the first 21-day breeding cycle. Keep in mind that heifer age at puberty and the percentage of heifers cycling at the start of the breeding season were similar between the two groups.
“So, we’re not only impacting weaning weight and carcass weight of the steers, we’re impacting the fertility of heifers before they’re ever born,” Funston said.
In another three-year study, Funston and his peers examined the effects on progeny of winter supplementation (last trimester) to cows grazing winter range or corn crop residue. The supplemented group received 1 lb. per day of a 30% protein supplement.
Heifers from cows grazing winter range and supplementation had pregnancy rates 14% higher than those from non-supplemented dams. Heifers from cows grazing corn crop residue and supplemented had pregnancy rates 5% higher than those from non-supplemented dams.
Steers in the study from non-supplemented dams were significantly lighter at harvest and Quality Grade was significantly less.
“By not supplementing the dam, we took marbling away from the calf before it was ever born,” Funston said. He emphasized the supplementation was a pound of 30% protein supplement, not pouring feed to them in order to get the substantial gains.
Funston explained this fetal programming is associated with what’s termed epigenetics — basically the heritable changes in gene expression caused by something other than the underlying genetics.
Funston spoke during Thursday's ARSBC session focused on the nutritional influences on reproduction. Visit the Newsroom at www.appliedreprostrategies.com to view the PowerPoint slides and proceedings paper submitted by Funston to accompany his 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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