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All Breed Animal Model Is A Major Change
Dairy Pipeline: June 2007
Bennet Cassell
Extension Dairy Scientist, Genetics & Management
(540) 231-4762; bcassell@vt.edu
For all the years that bull proofs and cow indexes have been published by USDA, each dairy breed has been analyzed alone. No genetic or environmental information of any kind from other breeds was used. This policy ended with the May 2007 proofs, with the introduction of the “all breed” animal model. From this point on, records from all the different breeds as well as properly identified crossbred cows will be analyzed together.
This change doesn’t cause the published bull proofs to change very much, as the “all breed” evaluations are converted to a within breed scale before publication. However, the system makes better use of the information available to evaluate purebred animals, and generates proofs for crossbreds at the same time. A daughter of a Jersey bull out of a Holstein dam will now receive a genetic evaluation. At the same time, her performance will affect the proofs of both her Jersey sire and her Holstein dam.
The breed of the sire determines which breed base will be used to evaluate the crossbredcow, so in this case, her evaluation will be relative to the Jersey breed. Herds with two or more breeds of purebred cows – a Holstein-Jersey or Holstein- Brown Swiss mix for instance – may see some larger changes in evaluations of those purebred cows.
Cows of the “other” breed now
serve as contemporaries, helping to
evaluate environmental conditions
in the herd. In cases where only a
few animals of one breed are in a
herd, contemporary deviations can
change quite a bit in the process.
There are large breed differences in
genetic merit for production traits,
with Holsteins leading the way. On
the other hand, Jerseys are clear
leaders for productive life and
daughter pregnancy rate. Ayrshires
and Brown Swiss are the leaders for
somatic cell score.
The all breed animal model will help producers interested in crossbreeding make better predictions of crossbred performance of different breeds. Of at least equal importance, the system will allow us to predict the performance of daughters of specific bulls when crossed on another breed.