What goes into an ASBV
Meat & Livestock Australia December 20, 2023
What is an ASBV?
Australian Sheep Breeding Values (ASBVs) describe the genetic merit of sheep and goats across a range of traits within five major production categories: growth, carcase, wool, reproduction and health. Traits can be recorded throughout an animal’s life. For example, body weight can be recorded at birth, weaning, post-weaning, yearling, hogget and adult age stages. ASBVs are reported separately for all of these growth traits so that users can target the most relevant age in their selection. ASBVs are an indication of how an animal’s progeny will perform based on the genes they will pass on.
To calculate ASBVs, Sheep Genetics uses a range of information, including data collected on the animal (i.e. birth type, rear type), information collected on relatives, sire and dam pedigree, trait measurements, environment and genetic parameters of traits, such as heritability. If an animal has been genotyped, this genomic data also contributes to ASBVs.
ASBVs are reported using a specific format including the age stage, trait name, the ASBV itself, as well as the accuracy of the ASBV.
Sheep Genetics also provides selection indexes. Indexes are a selection tool that combines a range of traits into a single value that allows producers to rank animals across a range of traits at one time. These indexes are built on an economic model for different production systems, where higher indexing animals tend to be more profitable. These indexes also contain health and welfare traits like worm egg count, breech wrinkle and lambing ease.
Percentile bands are available on the Sheep Genetics website to help you identify how ASBVs and indexes compare to the rest of industry. Percentile bands illustrate the favourable direction of ASBVs, as larger numbers are not always better. For example, Worm Egg Count (WEC) is a measure of worm resistance, so a more negative number (or a lower worm egg count) is more desirable. Percentile bands identify what percentile the ASBV/index sits within (e.g. top 10%, or bottom 10% and everything in between). Without the percentile bands, ASBVs can be difficult to interpret. On the Sheep Genetics search site, animals in the top 5, 10 and 20% will be highlighted in purple, blue and green, respectively.
ASBV or index accuracy is another important tool. Accuracy figures are reported below the ASBV and are expressed as a percentage. The accuracy is a reflection of how much information is being used to calculate an ASBV/index, with higher accuracy breeding values being a better estimate of genetic merit. Higher accuracy breeding values are less likely to change when more information becomes available.
