General Session I
Economically Relevant Traits for Commercial Cow-Calf Production: Reproduction
by Troy Smith for Angus Productions Inc.
HOUSTON, Texas (April 19, 2012) — The beef industry has made significant advancements in cattle performance through genetic selection for growth traits, but nothing is free. That was the message shared by Colorado State University animal scientist Milt Thomas in a presentation to the 2012 Beef Improvement Federation (BIF) Research Symposium in Houston, Texas. Thomas cited evidence that the cost of increased growth may be reduced fertility.
Thomas explained research spanning several years and involving Brangus cattle grazed on the Chihuahua Desert of New Mexico. Results suggest increased cow size, resulting from emphasis on selection for growth traits, is associated with lower reproductive performance. In that environment, which is not unlike a large portion of the western United States, bigger, late-maturing cows exhibited reduced pregnancy rates.
“As cows got bigger, pregnancy rates declined,” Thomas said. “There wasn’t a huge effect, but there was a relationship — a slight opposing trend between cow size and pregnancy rate.”
According to Thomas, the research suggests cow size is dynamic across years, and it illustrated how environment poses limitations on production systems.
“I don’t want to go back to an 800-pound cow, but maturity curve is important to fertility,” Thomas said. “Early maturity is an economically important trait.”
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