Executive Summary
BOLT Single-Step EPDs Released
By Mark Anderson , NALF executive director
On August 27 , 2018 , the North American Limousin Foundation released BOLT Single-Step EPDs via International Genetic Solutions . NALF joined 11 other progressive breed associations in the multi-breed cattle evaluation system that will be released on a weekly basis . The other breed associations include : Red Angus , American Chianina , American Shorthorn , American Maine- Anjou , American Simmental , American Gelbvieh , Canadian Angus , Canadian Gelbvieh , Canadian Limousin , Canadian Simmental , Canadian Shorthorn .
Single-Step Incorporation of Genomics – Formerly , results from genomic tests were blended with an animal ’ s EPD after the bi-annual evaluation was complete . This method required frequent upkeep in the way of periodic recalibration and results only impacted the animal tested , not its progeny nor its ancestors . Going forward , the BOLT-derived EPDs will make use of genomic information along with all pedigree , performance , and progeny information , in one step ; thus , eliminating the postevaluation blending formula . Another crucial difference is that now , even animals who have not been tested will be impacted by genomic test results from relatives ; this can cause some major change in non-genotyped animals .
The actual release comes with base shifts on various EPD traits as we move to an across breed cattle evaluation . A good example of that is the docility EPD . Through the IGS calculation , the breed average now shifts to 12 versus 19 in the new BOLT system . Producers will have to adjust their eye on some of these
8 | OCTOBER 2018 trait ’ s , but the switch enables producers , both seedstock and commercial , to fairly evaluate cattle from one breed to another when comparing EPD data . Limousin cattle actually rank number one in the docility EPD in the across breed comparison thanks to the work that breeders did the last 20 years in positively addressing and fixing the trait .
The switch to BOLT reduces the standard deviation on traits and narrows the range from “ High to Low ” on all traits . Limousin actually shifts positive on calving ease , birthweight and ribeye size in the switch . Most all breeds decline 2-5 lbs . on average for weaning weight and yearling weight , but Limousin actually ranks in the top 2-3 on weight
Limousin cattle actually rank number one in the docility EPD in the across breed comparison thanks to the work that breeders did the last 20 years in positively addressing and fixing the trait
trait comparisons in the across breed evaluation with the change to BOLT . Limousin also shifts sharply upward on stayability and ranks near the top on the across breed , BOLT stayability EPD .
Calving Ease ( Direct and Maternal ) – In addition to the changes impacting all traits mentioned above , Limousin has a positive base shift on Calving Ease Direct from 9.4 to 12 . Calving Ease Maternal stayed near 6 . Yet , substantial updates were made that caused some re-ranking for CEM and CED .
Contemporary groups with no variation : In the past , if calving scores were submitted on heifers and there was no variation in the scores ( all 1 ’ s , for example ), the performance information on those calves was not used . Now , with single-step EPDs powered by BOLT technology , data on animals in contemporary groups without phenotypic variation can be used . For CED and CEM , calving scores from contemporary groups in which none of the heifers required assistance can be used . This means there is more information available for genetic prediction in the BOLT-powered EPDs , which should mean less bias .
For the Growth Traits , BW , WW , YW , MK , the old Cornell system utilized Meat Animal Research Center breed contrast . For the BOLT release , IGS partner data is now used for breed contrast on the weekly cattle evaluations . This has also shifted the base for the Limousin milk EPD from 27 to 21 . The new milk EPD calculation also relies heavily on actual performance data of Progeny that are reported for WW on the animal ’ s progeny . Keep in mind that the milk EPD evaluates differences in weaning weights between bull ’ s daughter ’ s calves ; is it better or worse than we ’ d expect given what we know about their genetics for growth ? If they weigh more