STRUCTURAL SOUNDNESS

New Leg Angle EBVs

Leg Angle EBVs are now published for Angus animals recorded with Angus Australia, including all AngusPRO animals, complementing the existing Claw Set and Foot Angle EBVs.

Leg Angle EBVs (Leg) are estimates of genetic differences in rear leg structure when viewed from the side.

Leg Angle EBVs are calculated from a subjective assessment of rear leg structure and are expressed in score units. Lower Leg Angle EBVs indicate an animal is expected to produce progeny with, on average, a lower score for Leg Angle (i.e. straighter angle through the hock joint).

Leg Angus EBVs are calculated using a similar analytical model to the model used for Claw Set and Foot Angle, including:

• a single trait, linear model

• facility to incorporate breeder-assessed scores, along with scores collected by an accredited assessor

• facility to incorporate multiple scores for each animal

• facility to incorporate scores both on yearling animals and mature females

• facility to incorporate genomic information into the calculation of EBVs

• facility to only incorporate scores of 5‒9 in the calculation of EBVs.

In contrast to the Claw Set and Foot Angle EBVs, scores are only included in the calculation of Leg Angle EBVs for animals recorded with Angus Australia. Leg Angle EBVs are not published for animals recorded with the American or Canadian Angus associations.

While many producers have successfully managed the structural soundness of their animals using different selection strategies, such as culling of animals with unacceptable structure, Claw Set, Foot Angle and Leg Angle EBVs provide a useful tool that breeders can use in association with existing management and culling strategies to further improve the foot and leg structure of their animals.

Claw Set, Foot Angle and Leg Angle EBVs have several major benefits when used in association with traditional selection strategies.

• Like all traits of economic importance, the foot and leg structure of an animal is a combination of the genetics it has inherited from its sire and dam, and a range of non-genetic effects. Claw Set, Foot Angle and Leg Angle EBVs take any differences in non-genetic effects into account and focus on the genetic differences between animals.

• The Claw Set, Foot Angle and Leg Angle EBVs calculated for an animal take into consideration not only the foot structure and leg angle of the individual animal, but also that of all its relatives. In this manner, the Claw Set, Foot Angle and Leg Angle EBVs provide a better indication of an animal’s genetics for foot structure and leg angle than an assessment of the animal for structure alone.

Claw Set, Foot Angle and Leg Angle EBVs allow for genetic differences to be identified between animals that themselves may have acceptable foot structure or leg angle. Animals that have acceptable structure but are likely to produce a high percentage of progeny with poor structure can be removed from the breeding herd, or conversely, if two animals of similar genetic merit for other traits are being compared for use within a breeding program, the animal that is likely to produce a higher percentage of progeny with superior foot structure and leg angle can be selected.

Calculating Structural Soundness EBVs

While not applicable for Leg Angle EBVs, the Claw Set and Foot Angle EBVs published by Angus Australia are calculated in an international Angus genetic evaluation where structural score information on Angus animals born in New Zealand, Australia, the United States and Canada is combined to calculate a single EBV.

The EBVs are calculated based on more than 100,000 structural scores that have been collected across the four countries on both yearlings and mature cows, with animals scored multiple times during their lives. In addition to structural scores, genomic (or DNA) information is also incorporated into the genetic evaluation, adding considerable accuracy to the EBVs that are published.

A unique feature of the EBVs published on AngusPRO animals is that they can be directly compared with the breeding values published on Angus animals in Australia, the United States and Canada, enabling the genetics of AngusPRO animals for structural soundness to be benchmarked within the international Angus gene pool.