Whether you buy or develop replacement heifers, selection and development is key to their long-term success and productivity in your operation. Here are some considerations for selection and development of replacement heifers.
1. Select heifers born early in the calving season.
Research by Rick Funston of the University of Nebraska shows heifer calves born during the first 21 days of the calving season had greater bodyweights at pre-breeding and pre-calving, greater percent cycling before breeding season and greater pregnancy rates compared with heifers born in the third 21-day period of the calving season.
Likewise, Bob Cushman with the U.S. Meat Animal Research Center reports heifers that calve early in the season with their first calf have increased longevity and kilograms weaned.
Earlier calving gives first-calf heifers more time to become reproductively sound prior to the next breeding season, increasing chances of conception and remaining in the herd. The increase in longevity and kilograms of calf weaned results in these heifers being more successful as cows and improving profit potential of the cattle operation.
2. Develop heifers to cycle prior to the breeding season.
Research by DJ Byerley at Montana State University and the USDA research facility in Miles City reports breeding heifers at pubertal estrus reduces pregnancy rates compared with breeding at third estrus. Therefore, heifers need to be cycling before the breeding season to have the best chance to conceive, become pregnant and remain in the herd.
3. Conduct pre-breeding exams to determine heifer cyclicity and if the heifer is big enough to calve with ease.
A veterinarian should perform the exam 30 to 60 days prior to the breeding season, or when heifers are 12 to 14 months old, if expected to calve as 2-year-olds. One part of the exam is reproductive tract scoring, which determines cyclicity and soundness of reproductive tract. The reproductive tract score ranges from one to five, where one is an infertile or immature heifer tract and five is a cycling heifer tract.
John Hall, a Virginia Tech University professor and researcher, reported 12-month-old heifers should have reproductive tracts scoring from three to five to become pregnant early in the breeding season, while 14-month-old heifers should have reproductive tracts scoring four or five.
Fourteen-month-old heifers not scoring a four or five prior to breeding have a reduced chance of cycling, becoming pregnant and calving as 2-year-olds. A guide sheet developed by the University of Arkansas Division of Agriculture reported that heifers calving as 2-year-olds showed a dollar return sooner and more calves through their lifetime, compared to heifers calving as 3-year-olds.
Since improved profit potential and lifetime productivity is associated with heifers calving as 2-year-olds, the heifers that have a reproductive tract score of three or less at 14 months old should be candidates to cull from the operation.
Pre-breeding exams also measure pelvic area to determine if the heifer will be big enough to have a calf without assistance. The veterinarian will measure the height and width of the pelvis through rectal palpation, which needs to be greater than 150 cm2. If the heifer’s pelvic area is greater than 150 cm2 and bred to a calving ease bull, she is less likely to need assistance when calving.
4. Check and manage body condition score at breeding and after calving.
At breeding, develop heifers to 65 percent of their mature weight and a body condition score (BCS) of 5 or better, characterized by visible hips, some fat over the hooks and pins, and the backbone is no longer visible. Optimum heifer conception at breeding happens at BCS 5.
At calving, develop heifers to 85 percent of their mature bodyweight and a BCS of 6, which is a smooth, fleshy appearance so the ribs are not visible. At BCS 6, it allows for loss of one BCS prior to breeding while still being in optimum BCS to conceive in the subsequent breeding season.
Between calving and breeding, first-calf heifers may not be able to eat enough and need to lose one BCS to meet high nutrient requirements of becoming reproductively sound, growing and lactating for the first time.
5. Breed heifers to calve one month prior to cows.
This allows first-calf heifers more time to become reproductively sound prior to the next breeding season, increasing the likelihood of conception and retention in the herd.
6. Pregnancy check and cull open heifers as soon as possible.
When discussing lifetime cow studies from Montana, Glenn Selk, Oklahoma State University emeritus animal scientist, notes that properly developed heifers exposed to fertile bulls and that did not become pregnant during the breeding season were often subfertile compared to heifers that did conceive.
Furthermore, these open heifers throughout their lifetime averaged 55 percent yearly calf crop. This shows open heifers after their first breeding season are subfertile and have decreased chance of conceiving and weaning calves in subsequent breeding and calving seasons.
Identifying and culling these heifers early reduces operation costs and increases profit potential by increasing the heifer’s ability to reach the Choice grade at slaughter.
Most veterinarians can determine a 45-day-or-older pregnancy by rectal palpation, but consult your veterinarian to determine optimum pregnancy check time as early as possible so subfertile heifers are identified and culled from the herd.
7. Consult your veterinarian on proper vaccination and deworming strategies when developing your heifers.
Vaccination usually starts from when heifers are 5 months old until prior to weaning, being vaccinated and boostered against IBR, BVD, PI-3, BRSV, leptospirosis, vibriosis and clostridia. Consider calfhood vaccination against brucellosis for heifers, which must be given in accordance with state and federal regulations by an accredited veterinarian.
Protect against reproductive loss by vaccinating heifers again against leptospirosis and vibriosis 60 to 30 days pre-breeding. Booster the leptospirosis vaccination at pregnancy check time.
Also, 60 to 30 days before breeding, season booster vaccinations of IBR and BVD, and consult a veterinarian on whether to use a modified-live viral or a killed-viral product as well as if further booster vaccinations are needed.
Proper heifer development and management is important to her success. Likewise, bull selection and immunization is equally important in making sure she has the calf with ease and passes on the best immunity possible to the calf, giving it a healthy, productive start.
Not all heifers make replacements, so it is important to identify those open heifers early on and cull them to get the best profit potential possible.
- Regional Livestock Specialist
- University of Missouri Extension
- Email Patrick Davis