Heifer Calving Rate EPDs

An American Hereford Association update is available for Heifer Calving Rate (HCR) EPDs.  This EPD is reported in percentage units for daughters calving rate, where a higher value is more favorable.  Whole Herd TPR has fueled the availability of this genetic selection tool for ultimate use in characterizing Hereford calving rate genetics for the membership and beef cattle industry.

The HCR EPDs are produced from an animal model genetic evaluation for 304,853 animals encompassing a six-generation pedigree.  Heifer calving records were analyzed as a categorical trait in which nearly 105,000 records were used in the binary analysis as calved and not calved, based on recorded calf birth date.  The contemporary groups were defined as herd, first-calf heifer yearling contemporary group, calf birth year and season.  A restriction of age at first calving between 600-800 days was used as part of edits along with checks for contemporary group variation.  Heifer calving rate for the dataset was 73%, under the criterion that the heifers calved by 800 days of age.  The heritability for heifer calving rate is .15, which is consistent with the magnitude of estimates for lowly heritable reproductive traits, but still allows for genetic progress.

The following example depicts a comparison between two sires for their HCR EPDs to describe genetic differences in future daughter calving rate.  Note that a higher value is associated with favorable genetic potential for calving rate in daughters.  As with other EPDs, the difference between individuals is the best approach to using the HCR EPDs.  With the economic impact of reproductive rate in beef cattle operations, the appeal of HCR EPDs is always top of mind.  In the future these EPDs will provide the opportunity to include genetic evaluation results associated with reproduction to directly enhance the benefits of existing AHA selection indexes.

Example HCR EPD (%)
Sire A: HCR EPD =     8%
Sire B: HCR EPD =     2%
Difference     6%

Six percent more daughters of Sire A are expected to calve as heifers, 
compared with Sire B’s daughters.

Prototype Evaluation Results
The HCR EPD listing provided in the following download contains sires with a minimum of 20 daughters in the prototype genetic evaluation.  The average EPD for these sires is +2.7% with a range 
between -10.5 and +12.9%

>> Download sortable list (excel file)

— American Hereford Association staff

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