Improving the accuracy of EBVs for your animals in Wagyu BREEDPLAN by submitting performance data requires some planning so that you can get the best bang for your buck.
Australian Wagyu Association CEO, Dr Matt McDonagh explains how it works.
- A contemporary group is considered to be animals of the same sex, born within the same herd within a 60-day period and managed together as one mob.
- The size of a contemporary group influences the accuracy of EBVs – two in the group improves the results; six increases it significantly. Ideally, 10 in the group gives reasonable results for small herds.
- Heritability in most traits, such as marble score, is less than 50%, which means the majority of observed variation between individuals is not due to genes. The marble score trait is 30% heritable. This means that 70% of the difference between animals can be attributed to environment and management, not genes.
- Comparing animals in a contemporary group allows us to better determine the difference between individuals that is due to genes.
- Through BREEDPLAN, EBVs are calculated to give an indication of the animal’s genetic merit for production.
Wagyu BREEDPLAN is a genetic evaluation system that produces Estimated Breeding Values (EBVs) for a range of important production traits (eg. weight, carcase, fertility). EBVs are an estimate of an animal’s genetic merit for a production trait.
Included in the calculation of EBVs are the animal’s own performance, the performance of known relatives, the heritability of each trait and the relationship between different traits.
A range of factors influence how performance data is used within the Wagyu BREEDPLAN, with things like heritability (the amount of the observed trait that is due to genes) and contemporary group size being two important ones.
Heritability is the proportion of the trait expressed that is due to genes. Heritability of most traits is less than 0.5.
This means that for most traits, the majority of the phenotype you see expressed in an animal is due to the environment or management of the animal.
As a result, it is important to understand how animals raised within the same management group (contemporary group) perform against each other to determine the genetic variation between individuals.
A contemporary group is a group of individuals that were born together and managed as one group for their whole of life.
For example, a drop of steer calves from one paddock that are managed together, are then fed in the same feedlot pen and slaughtered at the same facility on the same day, are considered contemporaries. These ‘contemporaries’ have shared the same production environment whole-of-life.
Using their pedigree and DNA information, we are able to determine the amount of difference in their phenotypes that is due to their genes.
The effectiveness, and use of performance data to calculate EBVs is dependent on comparing animals within contemporary groups.
The more animals within a contemporary group, the more information can be extracted to determine the genetic contribution to the data. So how many do you need to give some quality results?
The effectiveness of an individual animal’s performance data to contribute to its own EBV within BREEDPLAN increases as a contemporary group size increases.
A performance record in a single animal contemporary group is not used by BREEDPLAN. It can be accepted and loaded, but it is not informative. It’s like trying to compare one apple to a box of oranges.
A performance record in a contemporary group size of two is 50% effective and starts to give some usable data to BREEDPLAN.
This increases as contemporary group size. Once you get past a contemporary group size of six, the benefit of more individuals in the contemporary group starts to level out for individual EBVs within the contemporary group.