Avoid heifer overconditioning

“About 25% of a dairy’s production costs are going to be in raising heifer replacements. So, they are not actually paying the bills right now, but they are costing a fair amount of money,” said Gail Carpenter.

Carpenter is an assistant professor of Extension and outreach in the Department of Animal Science at Iowa State. Her presentation was part of the university’s “Raising Your Best Dairy Heifer” series.

Managing heifer body condition can help ensure a return on that significant investment. According to research cited by Carpenter, overconditioning – when an animal is storing too much fat in her body – is a predictor of impaired mammary development.

As body fat increases, udder development decreases. “This poor mammary development will likely result in reduced milk production,” Carpenter said. Overconditioned heifers are also more likely to experience transition cow problems around calving.

The overarching goal is to achieve consistent body condition and avoid variation within a heifer group. The ideal scenario is a body condition score (BCS) of 3.25 to 3.5 at first calving, with a preference for the light end of that range to avoid overconditioning risks. Young heifers, closer to 12 months, should have a BCS of 3.

Underconditioning is also a risk factor, especially for hoof health issues and lameness, but Carpenter observed that overconditioning is the predominant issue on the farms she visits.

BCS is the key to assessing heifers. “You can’t manage what you don’t measure,” said Carpenter. BCS is measured on a scale of 1 to 5, with 1 being underconditioned. Scoring does take practice, but there’s no need to overcomplicate the process.

First, examine the heifer from the side to determine if she’s above or below a BCS of 3. This is accomplished by looking at the angle created by three points: pin bone (on either side of the tail head), the thurl (the joint where the leg attaches to the pelvis) and the hip (the larger bone at the front of the pelvis).

If the hip-thurl-pin angle creates a V-shape, the heifer has a BCS of 3 or less. If the angle forms a U-shape, she has a BCS of 3 or more.

Once it’s been determined that the heifer is over 3, switch to the rear view to assess the degree of overconditioning. Look at the sacral ligament and the tail head ligament. Seeing both ligaments clearly means she has a BCS of 3.25. If the tail head ligament is still visible but the sacral ligament less so, she has a BCS of 3.5. If neither ligament is visible, she has a BCS of 4 or higher.

BCS will likely not take place if it’s a standalone extra chore. For that reason, Carpenter encouraged a practice called habit stacking – attaching a new habit to an existing habit.

“Start paying attention to body condition while you’re breeding. Start paying attention while you’re doing dry-offs. As you’re doing things with those heifers, try to tack body condition onto it,” she said. She also said not to be afraid to bring in someone to provide a fresh perspective.

The aim is to monitor and manage BCSs while optimizing growth. The goal is to have the majority of heifers calving at 85% of mature body weight, and they should be bred at 55% of mature body weight.

Mature body weight, then, becomes a critical metric for proper nutrition. It’s useful for setting weight gain targets and essential for accurate ration modeling.

Body composition changes as animals approach maturity; it becomes easier to put on fat and harder to put on protein. Smaller-framed heifers with lower mature body weights will be closer to maturity and more prone to fat deposition than larger-framed heifers.

One feeding strategy to balance the needs of this generic variation among heifers is precision feeding. This requires feeding a higher grain diet but restricts intake below what they would normally consume. This strategy works well when grain prices are low and heifers have equal access to feed. If they don’t have equal access, dominant heifers will overeat while shy heifers get insufficient feed.

The other strategy involves feeding more bulk and lower nutrient forages while allowing as much intake as the heifers want. The heifers will feel satiated without overeating. It especially works well for older heifers with well-developed rumens. Carpenter made a pitch for switchgrass, a native prairie grass that is low energy yet provides bulk.

Feed sorting can also create variation among heifers. Sorting likely means that some heifers are over-consuming energy and some are under-consuming, resulting in BCS and weight gain variation. Pushing up feed, feeding more often or adding a liquid like water or molasses may also prevent sorting.

Making sure heifers get pregnant to calve at 85% of mature body weight is also important. Carpenter has been on farms with a huge variation in ages of heifers at first calving, which is not ideal.

“If they haven’t gotten bred when they need to get bred, they are more likely to be gaining in body condition,” said Carpenter. Having a good BCS at calving generally means that there will be less body condition loss and associated problems post-calving.

Carpenter said to pregnancy check at 30 to 45 days post-breeding and to quickly get open animals back on a breeding program. Pregnancy check again at 200 days.

Housing and stocking rates also factor into heifer development, often resulting in unequal feed access. This in turn impacts weight gain and body condition.

“We want to make sure that we’re breeding the correct number of heifers, and we want to make sure that every heifer that hits the ground on our dairy is set up so that she hits the herd as a healthy two-year-old,” Carpenter said.

by Sonja Heyck-Merlin