Cow-Calf Commentary for Iowa Cattleman Magazine
By Randie Culbertson, extension cow-calf specialist
May 2023
Development of heifers for breeding: Set them up for success!
The ability and success of a heifer to become pregnant, calve and rebreed have long-term implications for the financial success of any cow-calf operation. Proper management can greatly affect a heifer's success and longevity in the cow herd.
Puberty is a major factor contributing to a heifer’s success. For a heifer to calve as a 2-year-old, she must reach puberty and become pregnant at 12 to 15 months of age. Research has shown that conception rates for heifers increase by approximately 21% from the first to third estrous cycle. Heifers born earlier in a calving season will have an advantage over those born later. Earlier-born heifers will be older, allowing them to reach puberty sooner in the breeding season. In addition, heifers who conceive early have a higher probability of rebreeding as a 2-year-old, have greater lifetime production through heavier calves at weaning, and tend to calve earlier in subsequent years.
Meeting a heifer’s nutritional requirements is crucial for reproductive success. When a heifer partitions nutrients for various body functions, those nutrients will be allocated to growth before estrous cycles and pregnancy initiation. If a heifer's nutrient requirements are unmet, she will fail to cycle and ultimately fail to breed. Traditional recommendations have been to feed heifers to reach certain percentages of their expected mature body weight based on production stages. The general rule of thumb has been to develop heifers to approximately 60-65% of their expected mature body weight by breeding time. Some research suggests heifers could be developed to 50-57% of their mature weight, reducing development costs without losing reproductive performance. While there is some disagreement in the target weight of a heifer for breeding, nutritional management during this phase is critical for heifer breeding success.
While underfeeding a heifer through inadequate nutrition results in impaired reproductive function, overfeeding growing heifers can also lead to problems. Overdeveloping heifers can lead to suppressed estrus resulting in reduced conception rates and a higher incidence of embryonic mortality. In addition, overfeeding heifers can result in decreased mammary gland development and a reduction in milk production, known as fatty udder.
Puberty in heifers can be induced using the exogenous hormone progesterone. Using estrus synchronization protocols specifically designed for heifers has shown to be very effective in initiating puberty in heifers. However, the use of hormones for the induction of puberty is most successful for heifers approaching their age of puberty. Estrus synchronization protocols should be used in conjunction with appropriate nutrition protocols for heifers. For more information, check out the Iowa Beef Center's Estrus Synchronization Planner.
Consider breeding your heifers 3 to 4 weeks before your mature cow herd. This will ensure heifers will calve before the mature cow and help maintain a tighter calving distribution. At calving, heifers are typically more labor-intensive than mature cows, so having heifers calve before the main cow herd allows you to focus labor and attention when and where it’s needed. In addition, having heifers calve early allows the heifer more time to recover before rebreeding. First-calf heifers are still growing when they calve and require more time before resuming estrous post-calving. Early breeding of heifers will set them up for success by allowing them more time to recover once they calve and providing them the opportunity to breed earlier in the subsequent breeding season.
As you develop your heifers for breeding, you should also consider strategies for reducing calving difficulty. Meeting target weights for your heifers is the first step. Second, breed your heifers to the right bull. Choose calving ease bulls to reduce your incidences of dystocia during calving. And finally, if you are meeting target weights and choosing calving ease bulls but still have a problem during calving season, consider using pelvic measurements. Pelvic measurements should be used as a tool for culling, not selection. In other words, cull the heifers with pelvic measurements that fall in the bottom 10 percent.
In conclusion, providing the right conditions for a heifer to achieve reproductive success is crucial for the overall productivity and longevity of the cow herd. Your heifers are the next generation of your cows and you want them to be in your herd for years to come. Develop your heifers with a mindset for a lifetime of success.
