The saying 'you only get out of something what you put into it' is particularly true of performance recording for genetic evaluation purposes. While it is possible for animals which have little or no performance data recorded to have estimated breeding values (EBVs), this TechTalk explains the benefits of recording as much trait information on your animals as practical.
Specifically, this article (published by MLA in three parts in coming weeks) will discuss how we use recording to identify genetic merit, how recording more information can increase EBV accuracy, how identifying curve benders is impossible without recording, why recording is still important with genomics and how trait records can be used for non-genetic purposes.
In addition, this TechTalk series will discuss how to find out what traits have been recorded for each animal on the BREEDPLAN database and the value of recording traits for which BREEDPLAN does not currently calculate EBVs.
Identifying the genetic merit of your animals
With genetics, what we see is not always what we get. This is because environmental factors also have a considerable influence on most production traits. Therefore, we cannot simply say that all of the observed differences in performance between animals raised in different environments and/or different management groups is due to their genetics.
In the example illustrated in Image 1, we are comparing three bulls used on three different properties that have differing levels of feed availability. Based purely on the raw average yearling weights of each bull’s progeny, it is impossible to know whether Bull B has superior genetics or whether his progeny’s heavier weights are a function of the environment in which they were raised (on irrigated pasture). Nutrition is just one of the many environmental factors that can influence production traits. It is important to note that these factors can occur not only between properties, but between mobs and even within a single mob on a property. Two classic within mob examples are the presence of twins or individuals being sick or injured in an otherwise healthy herd.
Image 1: The average progeny yearling weight of Bull A, Bull B and Bull C, where the progeny were bred and raised on different properties.
The BREEDPLAN analysis removes the environmental factors from each animal’s raw performance and calculates EBVs. To achieve this, BREEDPLAN uses three sources of information; these are pedigree, trait records (from the individual itself and its recorded relatives) and, for some breeds, genomic information.
To allow BREEDPLAN to compare animals in different management groups (e.g. the scenario in Figure 1), there needs to be a genetic link between each group and/or property. A sire used in multiple groups passes on the same genetic merit regardless of the group (or environment) he is used in. Therefore, by comparing the progeny of the link sire against the progeny of Bulls A, B and C on each individual property, we can evaluate the relative genetic merit of all the bulls involved.
As Image 2 shows, the progeny of Bull A were 10kg heavier on average at 400 days of age than the link sire’s progeny, while the progeny of Bull B were on average 10kg lighter at 400 days of age than the link sire’s progeny. The progeny of Bull C were on average 20kg heavier than the progeny of the link sire at 400 days of age. Given that the genetic merit of the link sire does not change (e.g. any difference in average 400 day weight of the link sire’s progeny on each property is due to environmental factors), we can deduce that Bull A and C are genetically superior to the link sire for 400 day weight, and Bull B is ...
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