By Dana Zook
Over the past year, heifer retention has been a hot topic due to weather conditions and the declining cattle herd in the United States.
Although the number of heifers sent to the feedlot has increased according to a recent inventory report, local producers still retain some heifers to grow for their own use. For this reason, beef producers who have retained replacement heifers may be interested in research reevaluating heifer development guidelines.
When is the best time to breed a replacement heifer? Traditionally, guidelines suggest that heifers be at 60-65% of their adult body weight at breeding time. However, over the past 20 years, researchers have had success breeding heifers earlier and at lighter weights (50-59% of adult body weight).
As would be expected, breeding heifers at 55% of their adult weight results in fewer input costs. Waiting to breed heifers to 65% of their adult weight will obviously result in higher costs, but more of these heifers will be expected to become pregnant purely due to higher early weight. the projection.
Much research has been done to compare the performance of heifers grown at different weights. One such study conducted at the University of Nebraska (Funston and Deutscher, 2004) found that developing heifers to 53% versus 58% of adult body weight (based on 1,200-pound cows) reduced costs development of $22/head. In this study, heifers cycling at the time of breeding were 74% and 85% in the lighter weight and heavier weight groups, respectively. Pregnancy rates were very good overall; 92% for the light weight group and 88% for the heavy weight group.
Why would a producer take the risk of breeding heifers early and then finding that some of them were not bred? There is evidence that by trying to breed heifers earlier, there is a risk that a greater percentage of them will not become pregnant. For producers who are considering breeding heifers early but are concerned about reduced pregnancy rates, I would suggest keeping more heifers than necessary. Additionally, those who know their adult cow’s weight and current heifer weights can do some quick calculations to see if heifers are candidates for early breeding. For example, a producer with mature 1,200-pound cows can traditionally begin breeding heifers after they reach approximately 720 pounds (60 percent of adult body weight). This same producer, wanting to target heifers for breeding at 55% of adult weight, would raise heifers weighing approximately 660 pounds.
The discussion of heifer development lends itself to a much broader topic of cow efficiency. By decreasing the age at which a heifer is bred and has her first calf, the future cow is more likely to produce more calves during her lifetime. Research has shown that precocious heifers will become pregnant earlier than cows, increasing the number of pounds of calf they wean over their lifetime. Calves born earlier are naturally heavier at weaning, meaning more weight for market or the next stage of production.
Why can we now breed heifers earlier? The intensification of research has enabled the development of new ideas, but our cow herd has also definitely changed over the past decades. Research suggests that the establishment and increased use of EPDs has contributed to changes in reproductive performance. Additionally, the genetic tendency toward increased body weight of adult cows in many breeds has impacted age at puberty.
A lot of research has been done on heifer development, and there really isn’t a right or wrong way. Producers must be realistic and apply the method that best suits their financial situation, production methods and available resources.
Nutrition will account for a large portion of the cost of developing heifers, regardless of the method chosen. Seek nutritional assistance from your county Extension educator, regional specialist, or nutrition consultant to ensure nutritional costs associated with development are moderated.
Zook is a northwest region livestock specialist for the Oklahoma Cooperative Extension Service.
