Guide to Superior AI Beef Bulls

Expected Progeny Differences (EPD's)

The evaluations of the commercially important traits such as growth and carcase conformation are expressed as Expected Progeny Differences (EPD's). All EPD's are referenced to a Holstein/Friesian base. Therefore, a bull's EPD for growth is the difference in kg of carcase between the steer progeny (slaughtered at approximately 26 months of age) of the particular test bull and progeny of standard Holstein/Friesian parents reared under the same conditions and slaughtered at the same age. For example, if a Charolais bull has a "Growth EPD" of 50 kg it indicates that the carcases of his steer progeny from Holstein/Friesian cows are expected to be 50kg heavier than standard Holstein/Friesian steers at 26 months of age. The average weight of the Holstein/ Friesian carcases in the progeny test programme was 350kg.

Conformation scores are converted to a numeric scale. Thus grades EUROP are converted to 5, 4, 3, 2, 1 respectively. The average conformation of the Holstein/Friesian test steers was 2.02 or slightly to in the O grade. Therefore, a beef bull showing a conformation EPD of 1.0 is expected to produce steer progeny from Holstein/Friesian cows of conformation score 3.02 or slightly into the R grade.

Linear Scoring and BLUP

Not all bulls in AI have been or can be progeny tested. Fortunately, the development of linear scoring in the Limousin, Charolais and Simmental Pedigree herds provides very useful information on the breeding values for muscling, size and functional traits. Trained technicians score animals at approximately 7 months of age for muscular development, skeletal development, functional traits (legs, joints, etc) and breed characteristics. These linear scores plus the values on the bulls relatives (ancestors, siblings and progeny) can then be subjected to the BLUP technique for genetic evaluation to generate predicted breeding values for the measured traits. In some cases predicted 200 day and 400 day weights are also available.

The breeding values are usually expressed in index form. The index has been scaled to a mean of 100. In the case of Charolais, Simmental and Limousin the current base year is 1995. The base year is changed periodically.

With genetic progress the average of calves born in succeeding years will improve. For example, in the case of Charolais, the average of calves born in 2001 is 108 for muscle and 105 for skeletal and for Simmental the average of 2001 born calves is 105 for muscle and 102 for skeletal. In the case of Limousin, the average for 2001 born calves in 108 for muscle, 106 of skeletal, 104 for functionality and 105 for docility.

Reliability

All predicted breeding values should be read in conjunction with the associated reliability score, which is an indication of the amount of confidence that can be placed in the figures.

Young bulls with no progeny assessed will typically have a reliability rating of 30% to 45%. A mature bull in AI with large numbers of progeny scored is likely to have a reliability rating of over 80% in which case the actual performance of the progeny will be close to the predicted performance.

Progeny Tested Bulls

Maternally Tested Charolais

Maternally Tested Limousin

Simmental

There is no maternal testing in the Simmental breed but the following bulls are considered to have strong maternal traits on the basis of progeny or back breeding.

Bulls with serious calving difficulty % greater than 4.2 are above average for the breed. Some do not yet have calving survey results available, check with AI Organisation before use.

The functionality score (FUN) which indicated the quality and correctness of a bulls bone structure, joints, legs, etc. is shown in the above table as it is an important trait in the breeding of replacements.

BLUP scores suggest that some of the bulls listed also have strong terminal beef traits.