Yearling heifers need to be on a good plane of nutrition to meet their growth needs. “Because mature cows will maintain body weight on moderate-quality forage, some ranchers forget that growing yearling heifers will not gain the weight they need to reach puberty on the same quality of forage,” says Bob Larson, DVM, PhD, Dipl. ACT, Dipl. ACVPM, Kansas State University.

“Depending on the timing of the breeding season relative to forage quality and quantity, it is unlikely that heifers that grew slowly during the winter months will be able to gain enough weight on lush growing forage to reach puberty in time for the start of the breeding season.”

Larson explains that the onset of puberty is primarily influenced by age and weight, so heifers need to be gaining sufficient weight to attain puberty before the start of the breeding season.

In much of the U.S., forage availability in the winter is limited to standing dormant forage or baled forage. Only high-quality forage provides the nutrient density necessary to meet the gain requirements to reach the weights associated with the onset of puberty.

“If forage quality at this time of year is moderate to poor, yearling heifers are not likely to achieve the weight gain needed to reach puberty prior to the onset of breeding without supplementation,” Larson says. “Supplementing yearling heifers is required to meet weight gain goals in most forage situations.”

Read more about creating reproductive momentum in the herd in the upcoming January 2013 Bovine Veterinarian.