WEST PLAINS, Mo. – For cow-calf producers, it is ideal to have one healthy calf on the ground per cow per year. Producers should also strive to have cows that are productive in the herd for many years. On average, a cow must stay in the herd for six years for the producer to break even on that cow’s initial investment along with yearly maintenance costs.

Proper selection of replacement heifers is key to having cows that produce a calf every year for many years. Further, with the current high cattle prices, weeding out any infertile or problem heifers from the herd as a yearling, allows producers to market those heifers to the feeder market rather than as cull cows later in life.

To set that heifer up for lifelong success, she need to reach puberty by 15 months of age to potentially calve at 24 months. However, roughly 35% of heifers do not reach puberty by 15 months. Later-maturing heifers can be identified through pre-breeding exams, which are performed by a veterinarian and include a reproductive tract score and pelvic measurement. These exams should be done at around 12-15 months of age, prior to bull turnout or artificial insemination.

The reproductive tract is scored from 1 to 5 in relation to the heifer’s puberty status. A tract score 1 is given to heifers with an infantile or underdeveloped tract. A tract score 2 is given to heifers that are not close to cycling but are not as underdeveloped as a score 1. A tract score 3 is assigned to heifers that are near puberty but not yet cycling. A tract score 4 is for heifers that have reached puberty and are cycling in the first phase of the estrous cycle where follicles are developing but the heifer has not ovulated. A tract score 5 is assessed by a heifer who is cycling and is in the second phase of the estrous cycle during which an egg has been ovulated and a structure called the corpus luteum is present on the ovary.

As the reproductive tract score increases, the heifer’s likelihood of becoming pregnant increases. Heifers with a tract score 4 or 5 are already cycling and will have more opportunities to achieve pregnancy when out with a bull than a heifer who is a tract score 1 or 2 and may not be cycling when the bull is turned out. Further, pregnancy rates are lower on a heifer’s first cycle, so it is best to have a heifer already through her first cycle when she is artificially inseminated or turned out with the bull. Heifers with higher-scoring tracts will achieve their first pregnancy earlier in life and, subsequently, calve earlier in the calving season. Because she calves earlier, she has more days to return to cycling again than later-calving cows in the same herd, and she is more likely to breed back successfully. This trend generally continues throughout that female’s life, allowing her to produce more calves and be more profitable.

Along with the reproductive tract score, a veterinarian can measure the pelvic area. Heifers with smaller pelvic areas are more likely to have difficult births. This leads to more work for producers, who may have to pull those calves, and it increases the likelihood of calf sickness or death. By selecting for larger pelvic areas, producers can decrease the number of difficult births and death losses, improving their bottom line. Producers should consider culling heifers with a pelvic area smaller than 150 cm to avoid the risk of losing the calf or heifer when she calves for the first time.

The pre-breeding exam is also a great time to assess heifers for other culling criteria such as bad structure or temperament. Many producers take advantage of having the heifers in the chute to give them vaccinations. Producers should consider giving these replacement heifers vaccinations for the following diseases to set their herds up for success:

• Bovine viral diarrhea (BVD).
• Infectious bovine rhinotracheitis (IBR).
• Bovine respiratory syncytial virus (BRSV).
• Parainfluenza 3 (PI3).
• Five common types of leptospirosis.

Ultimately, performing pre-breeding exams on all replacement heifer candidates before investing more time and resources into breeding gives the farmer the opportunity to assess each heifer’s potential as a future cow and identify which heifers would be better in the feeder market.

For more information about pre-breeding exams or heifer development, contact Elizabeth Picking at the MU Extension Center in Howell County at 417-256-2391 or at pickinge@missouri.edu.