First-calf heifers pose specific challenges for cattle producers from many aspects. First, there has been a two-and-a-half-year period of developing these females before any return on investment is received. Second, even after calving, these females are still growing, and their nutritional requirements are the highest they will ever be to ensure adequate nutrients for both the cow and calf she’s rearing. This directly contributes to the difficulties many cattlemen experience with getting these young females re-bred. To counteract these difficulties, ensuring these females are in adequate body condition score at calving will largely determine their ability to rebreed the subsequent breeding season.

The first-calf heifer should reach 85% mature body weight prior to having their first calf, which requires that these heifers be around a body condition score (BCS) of 6 (BCS range from 1-emmaciated to 9-obese). Research shows that skinny heifers with a BCS below 5 at calving may decrease subsequent pregnancy rates by 25%. Heifers continue to grow and mature as the calf develops, through the delivery of that calf, all while beginning milk production and the repair of the reproductive tract. These are all physiological stresses that require availability and utilization of large quantities of energy, not including returning to heat cycles in a short period of time. Additionally, this is why managing dystocia through sire selection and nutrition, as well as setting these young females up to calve on time, becomes so critical.

Opportunities for Maximizing Heifer Longevity

Sort Young Females from Mature Females

Typically, heifers are bred to calve prior to the cow herd to allow for additional post-partum recovery. In order to maintain a 365-day calving interval, cows need to conceive within an 82-day window (283 days gestation + 82 post-partum interval = 365 days). Again, she is being asked to do a lot while transitioning from baby teeth to adult teeth. Maintaining a 365-day calving interval increases the productive life of the young female, while decreasing excess cow costs, which increases overall profitability.

To ensure her ability to re-breed the subsequent breeding season, separating the young females (2-to-3-year-olds) from the older cows (4+ year-olds) helps eliminate adverse conditions for young females, which includes lack of feed intake and thus lower body condition scores. This reduces competition and simplifies the herd hierarchy, while providing the opportunity for targeted feeding strategies if necessary, such as providing an additional protein source or an ionophore.

Early Weaning Benefits on First-Calf Heifers Productive Life

Comparing cost benefits of early weaning (EW) versus conventional weaning (CW) as well as reproductive performance throughout the animals’ productive life were analyzed in a recent study. A systems dynamics model was used to capture main feedbacks influencing reproductive performance, specifically, BCS, post-partum interval (PPI) and pregnancy rate interrelationships. Early weaning was used as a leverage point for beef systems improvement, since early weaning eliminates the need for energy to support lactation, allowing females to allocate those nutrients for her own growth, or for uterine repair, or for growing next year’s big healthy calf.

In this particular study, EW calves were weaned at 70 days of age. Only the first-calf heifers that calved within the first 21 days of the calving season met the age recommendation for EW. Those females who conceived earlier in the breeding season as yearlings had calves eligible for the EW system due to their likelihood of calving within the first 21 days of the calving season. This greatly illustrates the importance of developing heifers to conceive early in the breeding season, so they can calve early and provide managers options and flexibility to counteract other inputs (lack of grass, high feed costs, etc.).

The model analyzed different components of the system, including cow production line, calf production compartment, stocker operation compartment, feedyard operation compartment and financial compartment. Multiple scenarios were conducted with varying results.

Two-year-old females that calved within a 21-day calving interval and EW calves had an increase in pregnancy rate of 11% and a BCS increase of almost 1.5 units prior to the next calving season compared to CW calves, which equates to 100 to 150 pounds of additional bodyweight. This increase in pregnancy rate increased number of calves per exposed female, however, decreased weaning weights of first calves by almost 300 pounds, since they were weaned months sooner than herd mates. Nonetheless, EW calves from one generation of replacement heifers proved to be a profitable management practice, with improved performance by early weaned calves in the backgrounding/stocker enterprise. Early weaning provides options and flexibility; however, it requires time, labor, and resources to capture additional value from EW calves via improved efficiency/gain, which should be considered prior to weaning calves.

Conversely, when allotting a calving interval of 42 days and then early weaning calves, PPI was decreased by 17 days. The model calculated a 7.1% decrease in average 3-year-old cull rates and a 1.2% increase in 3-year-old pregnancy rates. Similarly, this allowed for more females to remain in the herd longer to wean additional pounds over their lifetime. This would suggest that females calving >21 days in the calving season stand to benefit the most from early weaning, and doing so may prevent their falling out of the herd at a younger age.