THE NATIONAL BRITISH BELGIAN BLUE EVALUATION
what it does, how it works

Estimated Breeding Values (EBVs)

The only way to measure the true breeding value of an animal with certainty is to measure the performance of very large numbers of progeny. However, this is only possible for a limited number of animals and takes a long time. Instead BLUP, using all the records that are available, produces Estimated Breeding Values (EBVs) for each animal. With Beefbreeder, EBVs are calculated for the following direct and maternal traits (these traits have been chosen because they are among the most relevant for profitable beef production and because there are a sufficient number of records available for them):

Direct		Maternal
• Calving ease	• 400 - day growth	• 200 - day growth
• Gestation length	• Muscling score
• Birth weight	• Muscle depth
• 200 - day growth	• Fat depth

Popular bulls from the terminal sire breeds have a large amount of influence in the national herd. Consequently, most of the EBVs currently produced are designed to help breeders produce terminal sire bulls with high genetic merit for growth and carcase traits but which will not cause calving difficulties in commercial herds.

The 200-day milk EBV is the only maternal EBV currently published. All the other EBVs when published for purebred females refer to their potential as dams of terminal sire bulls. Selecting females with high 200-day milk EBVs will result in a herd of milky cows with good maternal ability. A bull with a high EBV for this trait will sire milky females so it is a useful EBV for suckler producers to look at when selecting a bull to breed heifer replacements.

Direct and maternal The performance of offspring in some traits is affected not only by their own genes and environment but also by their mother's genes and environment. Both males and females carry genes for aspects of maternal performance such as uterine capacity and milk production but only females get the chance to express them. Gestation length, calving ease, birth weight and performance at 200 days are all influenced by the cow's maternal ability as well as the animal's own genes but at the moment only the latter is split into direct and maternal components. BLUP estimates how much of the 200-day weight record is due to genes for the calf's growth (200-day growth) and how much is because of the cow's maternal ability (200-day milk).

The EBVs are expressed in the same units as they were measured (e.g. 400-day growth in kg; muscling score in points) and they are calculated relative to the average merit of Belgian Blue animals born in the base year. The average EBV of animals born in the base year for each trait is set to zero, the average Calving Value set to 2 and the average Beef Value is set to 8. Because all EBVs are expressed relative to a common base direct comparisons can be made across all Belgian Blue herds in Beefbreeder and also across time allowing measurement of genetic progress.

EBVs estimate the genetic merit of animals, but calves get only half of their genes from each parent.

Eg a bull with an EBV for Muscle Depth of +0.2 is expected to produce, on average, calves with 0.1mm greater eye muscle depth compared to calves sired by a bull with an EBV of 0.

Before the calf has any performance records of its own, the best estimate of its own EBV is half the sire EBV plus half its dam EBV.

EBV			A brief explanation...
200-day growth (kg) 400-day growth (kg)			Selection on high EBVs for these traits will result in faster growing calves. Selection for high growth rates also tends to result in an overall increase in mature size.
Muscling score (points)			Selection on high figures will increase the amount of visual muscle leading to better progeny conformation. Two points on the muscling score scale are equivalent to one EU carcase classification conformation class.
Muscle depth (mm)			Selecting animals with high muscle depth EBVs will increase muscle depth at 400 days and hence the lean meat content of the carcase.
Fat depth (mm)			Selection on low fat depth EBVs will result in less carcase fat. A 0.2mm change in fat depth is approximately equivalent to one fat class.
Birthweight (kg)			Selection for low birthweights will result in lighter calves at birth and hence fewer calving difficulties.
Gestation Length (days)			The lower the figure the shorter the gestation lengths of a bull's calves. A shorter gestation length is economically important because it reduces the calving interval. It also provides more genetic information on the correlated traits of birth weight and calving ease (a reduced gestation length results in easier calvings because birthweights are lower). Gestation length is measured in pedigree herds which use artificial insemination.
Calving ease (% of unassisted calvings)			The higher the figure the greater the percentage of a bull's calves which will be born without difficulty, ie +3 is preferable to ­3.
200-day milk (kg)			This is the maternal component of the 200 day weight record. The higher the figure the better will be the maternal characteristics (eg milking ability) of a bull's heifer calves.

Please note: EBVs cannot be compared across breeds.