The process of replacing open cows by raising or buying replacement heifers is an annual occurrence on cow/calf operations if herd size is to be maintained. The success of replacement programs can be measured in many ways, but always is largely driven by how heifers were selected and developed up to entering the herd as a mature cow. Selecting heifers that will succeed is the first step to building herd longevity.
Select heifers that are most likely to breed early in their first breeding season and have the capability to calve unassisted and raise a calf to weaning time. Selecting heifers based on age, genetics and phenotype (structure) are the fundamentals to aid meeting this goal. But before getting too far down the selection road, make sure to define herd profitability goals by outlining what the end product is and how it will be marketed. If you are a commercial producer this may be pounds, while seedstock producers focus more on genetics.
Early born heifers (from the first 21 days) are more likely to reach target weights and puberty prior to start of the breeding season. Research shows once heifers reach puberty, fertility greatly increases from the first to the third estrus cycle. Therefore, older heifers have more time to reach a third estrus prior to the start of the breeding season compared to younger counterparts (Note: this may vary based on breed and plane of nutrition). Genetic technology in the form of DNA tests is also available to gain insight into future performance, maternal and carcass traits a heifer may offer. The best way to use DNA testing is to test replacement candidates selected based on herd goals first. Use the genetic results to eliminate the outlier or tail end females that don’t fit the bill. Lastly, structure plays a key role in how heifers will hold up in their environment. Therefore, make sure to eliminate heifers with structural problems that may be passed on to future progeny or will decrease her herd longevity.
Why it Matters
Whether you are raising or buying herd replacements, the process of selection and development is critical to herd longevity. Selecting heifers that have the best ability to breed early in their first breeding season, increases the likelihood they will remain at the front of the cow herd for years to come. Research from Nebraska shows that heifers conceiving early in their first breeding season, continue to do so over their lifetime, while also returning more calves with heavier weaning weights through 5 lactations. While maternal and reproductive traits, are later to develop, and may nott be predictable at selection time, using proven dam and sire information can put selection pressure on reproductive success. In addition, progressive culling and dedication to herd goals will continue to improve the future cow herd.