This week’s IGS evaluation, which we expect will be loaded to CGen on Tuesday 17th November, will contain two new programs within the IGS EPDs for Shorthorn Beef.

In the past, there were often complaints about a lack of progression within the analysis. Currently the progression within the IGS analysis has been much faster, however progression also means changes to the outcomes, which can also be a concern for members. However, this will be the last of any major changes for 2020.


The first program will be a change to the MARC Breed adjustment factors used to determine carcase performance level for each breed. Whilst this will cause a shift in EPD values and breed averages, it will not affect the Rank % for purebred animals.

The second program follows on from a recent Shorthorn Beef board decision to allowing lifting the age in days range for ultrasound records to include animals that were up to 900 days old when carcase ultrasounded. This will see an increase in the amount of historic Shorthorn ultrasound data that is used in the evaluation and will cause some reranking of carcase EPD’s based on the information now available to the analysis.

Whilst change is always challenging, the board felt that extending the ultrasound age range to 900 days of age would accommodate the needs of all Shorthorn Beef breeders management systems, given there is a substantial amount of Shorthorn Beef ultrasound data historically collected between 700 and 900 days.

The net effect will cause re-ranking of some animals, particularly those linked to systems that scan at a later age, however will also accomodate those breeders who are not able to scan their animals younger.

Dr. Randie Culbertson, IGS, also explained the new MARC adjustments.

“As with any trait under selection, breed effects will change over time. As a result, US-MARC updates their breed effects annually and the IGS Multi-breed Genetic Evaluation is in the process of updating these breed effects for the carcass evaluation. The implementation of these updated breed effects will cause some changes in carcass EPD. When comparing the rank of bulls with a high percent of a breed, there will be a shift in the EPD value, but the bulls will still have the same rank among other bulls with the same breed percentage. However, reranking will occur when comparing one breed to another as well as different percentage composites.”

“An ongoing challenge of estimating carcass EPD is the lack of carcass phenotypes. This lack of phenotypes creates a real challenge for the genetic evaluation to appropriately account for breed differences. With traits that have limited records and breed comparisons within contemporary groups, using field data can lead to unreliable estimation of breed effects. In those cases, breed effects from scientific literature are often used. The advantage of using breed effects from literature is that the effects are derived from “clean” data and often from herds with breeding systems designed specifically to obtain these breed effects. In the case of carcass trait breed differences, the IGS Multi-breed Genetic Evaluation uses the breed effects derived from US-MARC.”

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About Shorthorn

The Shorthorn breed is truly unique, from their distinctive roan colour, to their rich breed history and most importantly, the wonderful community of breeders, there is nothing else quite like a Shorthorn.

The key to the Shorthorn breeds advantage lies in their balanced genetic profile, driven by market participation that has been developed and refined, after more than 200 years of genetic selection under Australian conditions.

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