Calving timing critical: vet


First 21 days optimal | Front-loading breeding season yields heavier cows, healthier calves

SWIFT CURRENT, Sask. — Front-loading the breeding season should result in heavier calves and healthier cows, says Dr. John Campbell of the Western College of Veterinary Medicine.

He told producers at the recent Foraging into the Future conference that they should target a 95 percent overall pregnancy rate with 65 percent of the females bred during their first cycle.

“Ideally, we’d like almost two-thirds of our herd to calve in the first 21 days of calving season so that they get the maximum amount of time after calving to recover and start cycling again,” Campbell said.

The calves will also earn more money. For example, a weight gain of 2.5 pounds per day at $1.50 per lb. for 21 days results in $78.75 additional revenue for each calf.

As a result, producers can lose $38,000 in a 300-cow herd with an average conception rate of 87 percent if only 21 percent of the cows conceive in the first 21-day cycle.

“We whine about prices, but we don’t worry about this?” he said.

Campbell said producers often blame the bull when a cow is open, but it’s more likely that the cow didn’t cycle.

It takes 50 to 60 days for a cow to cycle after having a calf.

“Cows that are in poor or thin body condition can take anywhere from 80 to 120 days to come back into estrus, which puts them behind the eight ball when it comes to the next breeding period,” he said.

Replacement heifers also take 80 to 120 days to come into estrus after their first calves, he said.

“We really need them calving preferably before the cows or at the very least in the first 21 days of the calving period so they have a fighting chance to become pregnant the next year.”

Bulls do have a role to play in determining which cows might cycle earlier.

“We know that (scrotal circumference) is actually related to fertility in the bull’s daughters and so those bulls with larger testes, those daughters tend to be more fertile and reach puberty earlier, which sort of links all those traits of getting cows cycling earlier,” he said.

Cows usually calve at the same time each year, which means producers should make sure they don’t extend the interval between calving and breeding.

Campbell said body condition score is a critical component of successful conception. Females should be at least 2.5 on the five-point scale at the beginning of the breeding season if they are to have a chance at successful conception.

Campbell said that even with a perfect cow and a perfect bull, Mother Nature dictates that successful conception happens only 60 to 70 percent of the time, and that’s better than some other species. Good body condition can only help, he added.

A study conducted in the 1990s when trichomoniasis was discovered in bulls in a Saskatchewan community pasture found that body condition score had a strong impact on conception, even in the presence of the disease, which causes abortions and infertility.

“We were doing BCS and weighing cows coming in and exiting the pasture and we could show that those cows that either gained more weight on pasture or cows that were in good condition coming into pasture were about twice as likely to get pregnant,” Campbell said.

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