Cattle producers consider selecting and developing replacement heifers as the foundation for building an efficient, productive cow herd.
However, the approaches producers use to identify which heifers to keep for herd replacement out of the calf crop vary with herd management and marketing.
Producers can expect to keep nearly one-third of the heifer calves produced for breeding to replace cows leaving the herd, according to John Dhuyvetter, North Dakota State University Extension livestock systems specialist at the North Central Research Extension Center.
“Typically, 12 to 15 percent of the cows in a herd are culled and marketed annually for a variety of reasons,” he says.
The primary reasons are that cows failed to breed or lost their calf. But cows are culled for being lame and structurally unsound or thin and unthrifty; having poor udders or a bad temperament; or producing lightweight, inferior calves.
If producers need to select replacement heifers while sorting calves for the sale market at fall shipping time and have limited information, the best option is heifer calves showing good size and development, Dhuyvetter advises. Those characteristics indicate the calves were born early in the calving season out of a good-producing mother. These heifers should reflect high fertility and will be less expensive and easier to grow to breeding weights.
The calves can be scrutinized further for desired type (width and muscle, depth and capacity, femininity), structural soundness (correct feet and legs and free movement) and acceptable disposition. When available, calving book notes on calving ease, sickness, the dam’s udder and other issues also can be useful for eliminating unneeded calves.
“Herds with good animal identification and production records have additional information to use in making selections,” Dhuyvetter says.
The records can contain information about the sire and dam, the dam’s lifetime production record for calving date and progeny performance, and the heifers’ actual fall weight, along with adjusted weight to equalize for age differences and in-herd ranking (ratio). Daughters of older cows that demonstrate regular breeding and good weaning performance by their progeny, don’t have birthing problems or need individual care, and of a suitable type and size would be preferred replacements.
When keeping calves beyond weaning, producers have additional opportunities to evaluate the calves by observing and measuring postweaning performance.
“Keeping additional heifers back for development and breeding provides the opportunity to identify which heifers might perform and maintain condition on a high-forage ration similar to what they will receive as cows,” Dhuyvetter says. “Additionally, by only keeping heifers becoming bred in a very short breeding season, or only retaining the earliest bred and selling those that are bred later or didn’t become pregnant, nature helps you select for fertility and adaptation.”
He notes that a consequence of selection for high-performing sires and continually retaining the biggest heifers likely is a substantial increase in mature cow weights through time. When cow size becomes an issue, it can be managed, in part, at the time of heifer selection.
For example, heifers weighing more than 650 pounds at seven months after weaning and off pasture are likely to grow into 1,600-pound or larger mature cows. Heifers weighing 500 to 600 pounds at this age may help moderate or maintain cow size in the 1,200- to 1,400-pound range.
Several new technologies are available to help producers select heifers more accurately and for traits not easily related to visual evaluation. For instance, ultrasound scanning can help producers evaluate carcass traits, if of concern, in developing heifers. Scans provide an objective measurement of rib-eye muscle area and subjective scoring of marbling, both of which are highly heritable. These measurements are associated with carcass value and can be used for carcass improvement.
Genomics are an even more recent tool in beef cattle selection, including replacement heifers. Several commercialized tests using small tissue, blood or hair follicle samples analyze for genetic markers associated with economic traits in heifers.
In addition to carcass marbling and feedlot performance, genomic scoring is available for calving ease, heifer conception and fertility, disposition, feed intake and efficiency, whether they are horned or polled, coat color and defects. A test also is being commercialized for heterozygosity (having dissimilar pairs of genes for any hereditary characteristic) as a tool in managing crossbreeding.
“The intent at the time a heifer is held as a replacement is she will efficiently produce high-value calves for you during the next 10 years,” Dhuyvetter says. “In addition to using sires most likely to pass the needed maternal characteristics on to his daughters, we have to select the best heifer prospects for building a better cow herd.”