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Understanding Genetics

Photo: Errol Brumpton uses ASBVs for the modern sheep (Courtesy Qld Country Life)
Photo: Errol Brumpton uses ASBVs for the modern sheep (Courtesy Qld Country Life)

Genetics is the knowledge of how genes affect the way an animal looks or performs. It includes ‘heritability’, which describes how much of a trait is passed on from the parent to the offspring and ‘correlation’, which explains how one trait is related to another.

A wealth of genetics knowledge already exists and allows us to predict the performance of progeny, based on the performance of their sire or dam and other relatives.

The genetic merit of sheep and their estimated breeding values are predicted by directly measuring the performance of traits at particular times or by using indirect measures of a trait, that is, information about other traits that are related to the trait in which we are interested.

However, a sheep’s own performance is the result of both its genetics and the ‘environment’. The important environmental influences include nutrition, climate, diseases and parasites, whether the animal was a single or twin, whether its dam was a mature ewe or a maiden, its sex, its age relative to its flock mates and other factors about how the animal was managed.

To predict the performance of a sheep’s progeny based on its genetics, we need to exclude the environmental factors. Also, to increase the accuracy of this information we include performance data from its relatives: its sire and dam, siblings and half-sibs (i.e. brothers and sisters and half-brothers and half-sisters) as well as other relatives, especially the individual’s own progeny.

The result calculated is the ‘estimated breeding value’. For sheep in Australia, this is calculated and published as an Australian Sheep Breeding Value (ASBV) in LAMBPLAN (for meat sheep breeds) or MERINOSELECT (for Merinos). When ASBVs are calculated they also incorporate all that is known about the heritability of a trait and the correlations it has with other traits.

ASBVs are more accurate than using the raw measurement from a trait, especially for traits that have lower heritabilities, a smaller range of expression or lower accuracy of measurement. ASBVs also allow unrelated animals from different studs under different management conditions to be compared objectively.

ASBVs are only available for sheep when performance data has been collected using procedures outlined in the Sheep Genetics’ Quality Assurance Manual. Many sheep studs provide ASBVs for a range of traits on each of their sheep.

The Sheep CRC conducts genetic research through its Information Nucleus. This is a group of 8 flocks located across Australia, using many breeds and diverse industry sires to:

  • Establish new traits eg. Intra Muscular Fat and Shear Force (tenderness)
  • Develop genomic (DNA) tests for expensive or difficult to  measure traits
  • Improve the knowledge about genetic parameters
  • Expand the performance data across more bloodlines
  • Increase the availability and accuracy of Australian Sheep Breeding Values.


Choose from the tabs below to find more detailed information.


Practical Wisdom Notes Products & Training Resources Reports, Articles and Presentations Websites

Practical Wisdom Notes / Fact Sheets

Practical Wisdom Note - Using ASBVs

ASBVs stand for Australian Sheep Breeding Values. They are the national language for benchmarking sheep based on their genetic merit and are produced by Sheep Genetics. ASBVs describe a sheep’s breeding value for a trait, e.g. fleece weight or body weight, and express the relative breeding value of sheep across different breeding flocks of that breed (or across breeds in the case of Terminal breeds). They are equivalent to estimated breeding values (EBVs) used in other livestock industries e.g. BREEDPLAN in the beef cattle industry.

Products & Training Resources

ASBV Case Studies

Several case studies are available on the use and benefits of ASBVs - download the individual case studies below.

Australian Sheep Breeding Values - A guide for ram buyers

This guide is provided to help you understand the complexities of breeding profitable yet functional sheep that are right for your business.

Merino Sheep Breeding Trainer Guide

The Merino Sheep Breeding Trainer Guide has been developed by Sheep CRC and Meat & Livestock Australia to allow vocational and education trainers (primarily in the TAFE, Agricultural College and School systems) to deliver up to date knowledge and skills in the area of Merino breeding to their students. It is designed to be used in conjunction with three Power Point presentations, produced by the Sheep CRC on developing a breeding objective, selecting a stud and rams and selecting ewes.

Visual Scores Guide

Visually assessed traits are included in the breeding objective of all stud and commercial sheep breeders, regardless of their target market or environment.

Reports, Articles and Presentations

Getting Started with Sheep Genetics

Sheep Genetics provides you with practical information on the genetic potential of your sheep. Sheep are ranked according to various production characteristics using Australian Sheep Breeding Values (ASBVs) across flock or Flock Breeding Values (FBVs) within flock. See Sheep Genetics brochures available for download below. To download other publications click here.

Publications - Genetics

Download the genetics publications below.

Sheep CRC 2010 Conference Papers - Genetics

This Conference combined world class science with its practical application.

Sheep CRC 2010 Conference Papers - Sheep and their management

This Conference combined world class science with its practical application.

Sheep CRC Genomics Breakfast Workshop - LambEx 2012

During LambEx 2012 the Sheep CRC hosted a genomics breakfast workshop - download the papers from the workshop below.

SNP Chip - revolutionising genetics

This article appears courtesy of Meat & Livestock Australia (

Wool meets Meat - 2006 Conference Papers - Genetics

These proceedings are from the showcase conference of the Australian Sheep Industry CRC 'Wool meets Meat - tools for a modern sheep enterprise' conference held in Orange (NSW) during 2006.

Web Sites