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EBV’S. ESTIMATED BREEDING VALUES. WHAT IS AN EBV?. It is a genetic prediction of the average performance of an animal’s progeny or a prediction of how the animal is going to perform as a parent.
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EBV’S ESTIMATED BREEDING VALUES
WHAT IS AN EBV? • It is a genetic prediction of the average performance of an animal’s progeny or a prediction of how the animal is going to perform as a parent.
EBV’s are expressed in the units of the particular trait. E.g. 600 day weight is measured in kg, scrotal size in cm and calving ease in %.
An EBV can be generated for any trait as long as there is variation within the trait and the trait is of known heritability. • To develop an EBV, raw data has to be collected from a group of animals that have all been treated the same. • The raw data is then adjusted so all animals within the group are compared on a ‘level playing field’. E.g. weaning weights have to be adjusted for the date of birth of the calves and the age of the cows.
Once adjustments are made the computer then: • Calculates an average performance figure for the group for each trait. • Compares each individual animal within the group with this average, so that each animal has performance figure, which is above or below the average. • Multiplies this difference from the average, for each animal, by the known heritability of the trait.
Example A group of Angus 20 – month bulls have been run together since birth and have been treated the same. The group is weighed at 600 days and their weights are adjusted for age to put them on a level playing field. Assume the average adjusted weight for the group is 700kg. If one of the heavier animals within the group (Al Capone) has an adjusted weight of 760kg then he is 60kg above the group average. This 60kg is made up of weight due to the activities of Al Capone’s genes (genetic effects) and that due to feeding and animal health etc.
In assessing an animal’s breeding potential (EBV) we are only interested in the genetic part of production, because this is the only part we can influence through selection. To find out how big this genetic production is, we multiply the total production advantage Al Capone has over the average animal within his group i.e. 60kg,by the genetic strength of the 600 day weight EBV (its heritability which is 0.3 or 30%)
This gives Al’s within herd EBV for that trait. It is assumed that the average EBV for 600 day weight for the group is 0kg. Therefore Al’s within group EBV for 600 day weight is: (760 – 700)kg x 0.3 = +18kg The computer then uses performance information from Al’s relatives in other management groups as well as known genetic relationships between traits, to fine tune this basic within group EBV so that Al can be directly compared with all animals within the same evaluated population.
How does EBV relate to profitability? • The offspring of a bull with an EBV for 600 day weight of 130kg will be 65kg heavier and return nearly 15% more profit than the offspring of a bull with an EBV of 0.
In a simple beef finishing system, the most important trait to consider is growth rate, as the sooner the cattle meet target liveweights: • The more efficient the animals are at converting feed into beef • The sooner the monetary returns are received • The more likely the animals will attract early- season premiums • The more likely the producer is to avoid that period of the year when there is a dramatic decline in pasture quality, with corresponding poor cattle growth rates.
To summarise • An EBV is a prediction of the genetic value of an animal as a parent. • The average genetic performance of the offspring of a bull and a cow will be determined by the average of the EBV’s of the parents. However, environmental influences may alter the expression of this. • EBV’s can be used as another tool to select stock for specific systems.
