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Implementing PAP EPDs

CSU geneticist explains difference in PAP scores, EPDs.

by Troy Smith, field editor

LOVELAND, Colo., June 22, 2018 — The success with which a particular expected progeny difference (EPD) value can be used to select for genetic improvement depends on whether the trait selected is high or low in heritability. In the case of the EPD based on pulmonary arterial pressure (PAP) scores as the indicator trait of tolerance to bovine pulmonary hypertension (BPH), the trait is at least moderately heritable. However, PAP EPDs don’t tell breeders all they need to know about selecting cattle for tolerance to BPH, commonly referred to as brisket disease.

That message was shared by Colorado State University geneticist Scott Speidel in a presentation delivered during the 2018 Beef Improvement Federation Convention June 20-23 in Loveland, Colo. Speidel said multiple genes likely play roles, as do non-genetic factors.

“We’re seeing the disease (BPH) in feedlots located at lower altitudes, so while elevation can have a large effect, so can other environmental factors,” explained Speidel, listing potential influencers such as animal age, body condition, parasite load, previous or current respiratory disease, weather conditions and diet.

Speidel cautioned cattle breeders to use PAP EPDs appropriately, and to not forget the importance of an animal’s own phenotype — its actual PAP score. He reminded the audience that PAP EPDs are based on parent, progeny and individual data, but noted how the phenotypic PAP of a given individual can vary with the elevation at which a PAP test is taken. Therefore, bulls can have similar PAP EPDs and different individual PAP observations, and bulls with similar PAP observations may have different PAP EPDs.

“PAP EPD is a predictor of whether a bull’s progeny are suited to elevation, while a phenotypic PAP is an indicator of whether the bull is himself suited to elevation,” explained Speidel.

Therefore, breeders considering sires for use via artificial insemination can use published PAP EPDs to rank the candidates. If a purchased sire is expected to reside at elevation, a breeder must consider the sire’s own PAP score, measured at that elevation.

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