HOW TO USE THIS ONLINE MAGAZINE
by clicking the arrows at the side of the page.
by clicking anywhere on the page. A slider will appear, allowing you to adjust your zoom level.
and move the page around when zoomed in by dragging the page.
and return to the original size by clicking on the page again.
by entering text in the search field and click on "In This Issue" or "All Issues" to search the current issue or the archive of back issues
a PDF of this magazine.
by clicking on thumbnails to select pages, and then press the print button.
a page via email, Facebook, Twitter and more.
TO VIEW PREVIOUS EDITIONS
, click the
button at the bottom of the screen.
Beyond the Bale : September 2019
52 ON FARM BACKGROUND Genetic improvement is a safe and permanent method to improve breech flystrike resistance in Merino sheep. SheepGenetics currently provides Australian Sheep Breeding Values (ASBVs) for the breech flystrike resistance indicator traits of breech wrinkle, breech cover and dag. These are useful and drive genetic improvement, however, the most effective genetic response can be achieved by selecting for breech flystrike resistance itself, but it is very difficult to do commercially. Routine data recording for genetic improvement of breech flystrike in untreated sheep is labour intensive and expensive on commercial sheep properties and falls into the basket of a very “hard to measure trait”. With the rise of genomic selection tools, often well suited to hard to measure traits, the questions was asked: “Can genomics assist with breeding for reduce risk of breech flystrike?” CAN GENOMICS ASSIST WITH REDUCING THE RISK OF BREECH FLYSTRIKE? Breech flystrike resistance is a difficult and expensive trait to measure and new research indicates that a genetic marker-assisted selection approach to breeding for breech flystrike resistance will be largely ineffective. However, genomic breeding values, well suited to hard to measure traits, may have a role to play because they harness all the sheep’s genomic information. WHAT IS GENOMICS AND HOW DOES IT WORK? Technologies for genomic and marker assisted selection have improved dramatically in recent years. Genomics can provide selection tools for difficult or expensive to measure traits, offering opportunities to increase the accuracy of identifying genetically superior animals for important traits. What is ‘genomics’? In a practical sense, it means that the DNA or genome of an animal is analysed for thousands of genetic markers, which are landmarks that describe the DNA profile. When a producer undertakes a genomic test, a tissue sample often from the ear or a drop of blood is collected on a card and submitted to a service provider who then establishes the information at all the genetic marker sites chosen in the test (tests vary in size from 800 to 15,000 to 600,000 SNPs or sites). Results of a genome-wide association study for breech flystrike. The blue line indicates the chromosome- wide significance threshold. There are two potential avenues for how genomic information can be used in breeding for breech flystrike resistance, as a: 1. genomic breeding value (GEBV), which looks like an ASBV and is used in exactly the same way and does not require an animal to have breech flystrike phenotypes 2. genomic test, which is possible if a few genetic markers have a large effect on breech flystrike resistance and the test predicts the level of breech flystrike resistance. One requirement for a GEBV, is a reference population, which consists of several thousand animals that have been genomically tested and have been recorded for breech flystrike, such as the Breech Flystrike Resource flocks. With both approaches, breeders only require a genomic test, no phenotype, on their rams to obtain a genomic breeding value or a prediction of breech flystrike resistance. KEY FACTS • In a recent AWI-funded study undertaken by CSIRO, the use of the genomic information for breech flystrike resistance was explored, based on 1,500 sheep from the Breech Strike Resource flocks in NSW and WA. • The research indicates that unfortunately there are no ‘major’ genes associated with breech flystrike, breech wrinkle, breech cover and dag; instead these traits are influenced by many genes, each with small effects. Therefore, a genetic marker-assisted selection approach will be largely ineffective in breeding for breech strike resistance. • However, a genomic breeding value (GEBV), which looks like an ASBV and is used in exactly the same way, will be a more effective tool to add information about the associated traits of wrinkle, cover and dag but, it requires an expensive reference flock where sheep are monitored for the appearance of breech strike. Ways to create a cost effective ‘reference flock for breech flystrike’ will be explored.
In the Shops - September 2019