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Taking heifer reproduction to the next level

Published on 11 November 2010

Measuring, benchmarking and improving reproduction is a common goal within the milking herd. While the industry has a wealth of knowledge and information related to lactating animal reproductive performance, much less exists when it comes to heifer reproduction benchmarks.

Heifer reproductive performance is just as important to the dairy, since the sooner heifers can be bred and confirmed pregnant, the sooner they will join the milking herd and begin to generate revenue. Creating benchmarks and goals for your heifer program is critical to ensure replacement heifers join the milking string in a timely fashion.



Building a baseline
Research completed in 2006 by the Animal Improvement Programs Laboratory within the USDA provided some of the largest data pools to evaluate heifer reproduction. The data consisted of Holstein heifers that were artificially inseminated, with their first breeding taking place between March 2003 and August 2005. The final data set included 537,938 breedings of 362,512 heifers in 2,668 herds representing 41 states.

The study concluded:

• Average conception rate for Holstein heifers was 57 percent.

• Heifers at 26 months of age and older experienced about a 10 percent drop in conception rate compared to heifers bred at a younger age.

• Selection decisions using daughter pregnancy rate or cow pregnancy per artificial insemination (A.I.) can improve heifer fertility.


• Average age at first calving for heifers in the northwestern and southwestern United States was 25.2 and 25.6 months, respectively.

These results provided a baseline of information to help dairy producers measure their heifer reproductive performance against other dairies in the United States. It also showed there is room to improve heifer reproduction, regardless of current reproductive statistics.


Putting heifer reproduction into practice
Measuring your heifer reproduction program is the first step to making improvements. Table 1 outlines suggested benchmarking criteria and goals for getting heifers bred in a timely fashion.

To take heifer reproduction to the next level, it’s important to fully understand heifers’ reproductive cycle and the factors that directly influence their reproductive performance.

• The onset of puberty is based on weight. First ovulation signals the onset of puberty and is often attained when heifers reach 40 to 55 percent of mature body weight; in Holstein heifers this is about 550 to 600 pounds. Well-managed heifers can reach this size by nine to 10 months of age, so monitoring growth is critical to ensure animals reach breeding size in a timely fashion.


• Animals should be bred on size, not age. The age-old debate often causes much discussion about when heifers are ready to be bred. Once heifers reach weight and height benchmarks, they are ready to be bred. This means getting heifers to the appropriate size can happen sooner with a proper nutrition program and attentive, focused management.

• Heat detection is the critical step. Known as one of the most limiting factors for a lactating dairy cow’s reproductive performance, heat detection is also critical for a heifer’s reproductive performance. Heat detection aids can be used to achieve greater heat detection efficiency and accuracy, while keeping in mind the primary sign of heat is “standing to be mounted by a herdmate.” Secondary signs include clear mucus discharge, ruffled tail head hair, increased activity, mounting other heifers and chin resting.

1710pd_taking_tb_2 • Time matters. There is a limited window to breed heifers to maximize the opportunity for conception. Heats last about 10.8 hours for Holsteins and 12.7 hours for Jerseys, so knowing when standing heat starts can give you a head start to breeding animals at the appropriate time. Table 2 shows that the interval from first standing heat to time of breeding can directly impact pregnancy per A.I.

• Synchronizing heifers is an option. Using a synchronization program can ensure greater heat detection and labor efficiency, since the greater the number of animals in heat at the same time, the more likely they are to show heat and therefore the opportunity for breeding success is greater. Work with your veterinarian, artificial insemination representative or local extension agent to learn more about options available for effective heifer synchronizations.

• Check heifers early for rebreeding success. Check heifers before 40 days postbreeding to identify open heifers quickly and ensure a timely age at first calving. PD

References omitted due to space but are available upon request to

—Excerpts from Dairy Cattle Reproduction Council newsletter, Vol. 4, No. 1