Shorten the Breeding Season

April 19, 2016 07:00 AM

By: Laura Mushrush

Rate of gain, carcass quality, weaning weight, calving ease—the debate goes on for which beef production trait is most important. But really, it’s pretty simple: No calf, no profit and no other traits to measure. 

“Pregnancy has four times greater economic impact than any other production trait,” says Cliff Lamb, beef cattle specialist, University of Florida’s North Florida Research and Education Center (UF-NFREC). If producers want to maximize their herd’s potential, selection criteria must first be focused around fertility, followed by traits that suit the operations program, he adds.

“We spend a lot of time talking about genetic markers and traits, but not many people first ask how we can get a cow pregnant,” Lamb says. “And not only how can we get a cow pregnant, but how can we get her pregnant sooner?”

According to Lamb, a combination of estrus synchronization protocols with AI practices has greater payout for producers by enhancing reproductive performance, and not just giving them a broader genetic playing field.

“Right after a cow gives birth, she goes through a period called postpartum anestrus and doesn’t cycle,” Lamb says. “One thing that estrus synchronization does is kick start these cows to get them to start sooner.”

On average, postpartum anestrus will last from 50 to 90 days, Lamb says. While every cow is different, a cow 30 days out from starting to cycle again can typically start cycling earlier with estrus products.

“If you have a cow at 30 days postpartum who tends to start cycling at 60 days postpartum, she can be kick-started with estrus synchronization,” he says. “But if you have a cow that is 20 days postpartum and tends to start cycling at 60 days postpartum, she is in deeper anestrus and probably won’t respond to the products.”  

While the use of estrous synchronization and AI will increase time and labor for cow-calf producers, there is great value to capture.

According to Lamb, in the past five years, pricing components of timed AI haven’t changed much in price, including costs of semen, arm service labor and hormones. Meanwhile, the market for calves and herd bulls has greatly increased—making for great economic opportunity for cow-calf producers who utilize AI technology.

Research by USDA-Market Animal Research Center found heifers that became pregnant within the first 21 days of the breeding season had significantly greater longevity than heifers who became pregnant later in the breeding season. Furthermore, heifers who became pregnant within the first 21 days yielded calves with heavier weaning weights than
later-bred heifers.

Using this as a base, Lamb led a case study at UF-NFREC applying time pressure on breeding seasons over an eight year period using three criteria. First, the main selection trait is pregnancy. In other words, if she comes up open once, she’s gone. Second, to even the playing field, every female was exposed to estrus synch and AI protocols. Third, heifers must be bred within the first 25 days of the breeding season to be kept.

“There’s quite a lot of research that shows heifers that become pregnant in the 21 to 25 days of their very first breeding season have more longevity in the herd, become pregnant at a higher percentage every year for the rest of their lives and they produce calves with greater higher weaning weights than heifers who are bred later in the season,” he says. 

In 2006, before pressure was added, the pregnancy rate for a 120 day breeding season was 81% with a mean calving day of 79.2. By 2013, gradual pressure set the breeding season at 72 days, yielding a 93% pregnancy rate and mean calving day of 38.7. This pressure on fertility, increased calf value from $19,100 in 2008 to $50,700 in 2013. 

“As a result of using those three management criteria, the average calf in our operation has increased by $169 per calf compared to where we were six years ago,” he says.

This story appeared in the April 2016 issue of Drovers.

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