This article comes to us from Aaron L. Berger, Extension Educator, and Rick N. Funston, Beef Reproductive Physiology Specialist, both from University of Nebraska Extension. In the past several decades, post-weaning development of replacement heifers has focused on feeding heifers to reach a target body weight of 60 to 65 percent of mature weight at…
at breeding to achieve acceptable pregnancy rates (85 to 95 percent) in a breeding season that ranges from 45 to 70 days. This development system was based on historical research that indicated heifers bred at approximately 14 months of age should reach this target weight to achieve acceptable pregnancy rates.
In an effort to reduce costs, recent research has focused on comparing traditional, more intensive replacement heifer development systems to systems utilizing more inexpensive feed resources to develop heifers to lighter target body weights at breeding (i.e., 50 to 57 percent of mature weight compared with the traditional 60 to 65 percent of mature weight). Research has demonstrated replacement heifers developed to lower target weights — but on a positive plane of nutrition before the breeding season through calving — can have acceptable pregnancy rates and longevity.
These lower-input systems allow producers to develop replacement heifers at lower cost without sacrificing reproductive performance. This publication highlights why recommended target weights for replacement heifers have changed and key aspects of successful low-input replacement heifer development systems.
Why Recommendations for Heifer Target Body Weight at Breeding Have Changed
Genetic Selection
Much of the research recommending heifers be at a target weight of 60 to 65 percent of mature weight by breeding was conducted from the late 1960s through the 1980s. Since then, the genetic makeup of the U.S. cowherd has changed significantly. Age of puberty does not seem to be limiting heifer development programs as it did in the past. Heifers are reaching puberty at younger ages and at a lower percentage of their mature weight than has occurred historically.Research contributing to this publication was conducted using current British and Continental genetics in the United States. The following genetic trends have been realized by widespread management changes and the use of Expected Progeny Differences (EPDs) in the selection for a variety of traits, including scrotal circumference and yearling weight.
