A few tips about how many heifers to keep

Friday, October 27, 2017

Experienced cow-calf producers know firsthand the constant challenge in evaluating the number of replacement heifers that must be developed or purchased to bring into the herd each year.

“Producers have to match the number of cattle to available grass and feed resources, as well as maintaining cow numbers to match their marketing plans for long-term changes in the cattle cycle,” said Wes Lee, McClain County Extension director and agricultural educator.

As a starting place in the effort to answer key questions, it is important to look at the obligatory “average cow herd” to understand how many cows are in each age category. Research indicates the typical herd will, on average, introduce 17 percent new first-calf heifers each year.

“Stated another way, if 100 cows are expected to produce a calf each year, 17 of them will be having their first baby,” Lee said. “This gives producers a starting point in choosing how many heifers are likely to be needed each year.”

Next, cow-calf operators must predict the percentage of heifers entering a breeding season that will become pregnant. The prediction is made primarily upon the nutritional growing program the heifers receive between weaning and breeding.

“Researchers many years ago found only half of heifers that reached 55 percent of their eventual mature weight were cycling by the time they entered their first breeding season,” said Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist and editor of the university’s popular Cow-Calf Corner Newsletter.

A recent OSU animal science study reinforced this data. The research indicated if heifers were exposed to a bull for a limited number of days, 45 to 70 days in the study, not all would have a chance to become pregnant during the breeding season.

“In short, the research suggested it would be necessary to keep an additional 50 percent more heifers just to make certain enough bred heifers were available to go into the herd,” Selk said. “However, if the heifers were grown at a more rapid rate and weighed 65 percent of their eventual mature weight, then 90 percent of the animals would be cycling at the start of the breeding season and a much higher pregnancy rate would be the result.”

However, as most experienced cow-calf operators are well aware, some heifers are difficult or impossible to breed even in the best scenarios. As a result, most Extension livestock specialists and researchers write about the need to always expose at least 10 percent more heifers than the operation projects in needed even when the animals are grown properly and all weigh at least 65 percent of their expected mature weight.

Selk and Lee remind producers the need to properly estimate the expected mature weight is important in understanding heifer growing programs.

“Cattle type and mature size has increased over the last half century,” Lee said. “Rules of thumb that apply to 1,000-pound mature cows very likely do not apply in a given herd today. Producers should be mindful of sale weights of culled mature cows from their herd to better estimate the needed size and weights for heifers in their specific breeding operation.”

Most commercial herds today have cows that average about 1,150 pounds or more. This requires that heifers from these cows must weigh at least 747 pounds at the start of their first breeding season to expect a high percentage to be cycling when the bulls are turned in.

“These are good starting points in the decision to determine the number of heifers needed for replacements, but cow-calf operators must keep in mind the overriding need to understand how much their available forage base can accommodate,” Lee said.

Producers interested in additional information about stocking rates or retaining heifers should contact their OSU Cooperative Extension county office, typically listed under “County Government” in local directories.

Oklahoma is the nation’s fifth-leading producer of cattle and calves, according to USDA National Agricultural Statistics Service data.