Management Tools Improve Herd Fertility

COTTONWOOD, Calif. -- A few simple management tools can help ranchers maximize the fertility of their bull and cow herds, experts advise.

For instance, removing a calf from its mother for a couple of days has been shown to be effective at helping her begin estrus, said Les Anderson, a beef cattle specialist from the University of Kentucky.

Maintaining a healthy level of body fat helps a cow maintain a cycle without complications, and ranchers should bear in mind that younger cows sometimes take longer to cycle after calving, Anderson advised.

"One thing that has a direct impact on fertility that we can do a lot about is anestrus, when the cow can't come into heat," Anderson said, noting that postpartum anestrus occurs in every species. "It's how long the cows or heifers are in anestrus that determines the fertility of that cattle."

For one thing, cows during that period are starving for progesterone, so a seven-day treatment of progesterone has been shown to cause 80 percent of cows to start cycling, Anderson said.

When it comes to fertility, don't forget the bulls, recommends Bill Gray of the Cottonwood Veterinary Clinic. Ranchers should put their bulls through breeding soundness evaluations and tests for bovine trichomoniasis, check for eye lesions that could make it difficult for the bulls to spot estrus in cows, and treat or cull lame bulls, Gray said.

"The most common thing with these bulls is foot problems," he said, explaining the troubles could be caused by thorns, nails, rocks or even twine wrapped around the bull's foot.

The experts appeared at a workshop on herd health Feb. 26 at the Shasta Livestock Auction Yard in Cottonwood, put on by the University of California Cooperative Extension.

Anderson, a nationally known beef cattle reproductive physiologist, was the event's keynote speaker. He explained that a cow's estrous cycle is driven by communication from the brain to the pituitary gland, which sends out hormones that govern the reproductive process.

Cows with normal cycles are fairly easy to get bred, Anderson said. But one of the "critical control points of fertility" is the cow's expression of estrus through behavior, and in some dairy cows the average length of estrus is only about 7.2 hours, he said.

"It's not very long," he said, adding that other factors such as weather can also affect behavior.

Ranchers should vaccinate cows to prevent reproductive losses, said John Maas, a beef extension veterinarian at the University of California-Davis. Diseases that affect fertility can include campylobacter, leptospirosis and lepto hardjo-bovis, which is present in 50 percent of the beef herds in the U.S., he said.