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Online learning—Breeding and selection

This section desribes the processes for implementing a breeding and selection program that reduces the susceptibility of sheep to flystrike.

Structured reading

For those who like to see all the information and simply read through it in order. Each heading is a link to a page of information—the dot point provides a summary of the page.

Tip: Keep this page open and open the links in new tabs.

Breeding and selection
Overview of breeding for flystrike resistance.

Breeding to reduce flystrike susceptibility
Four steps to breeding for flystrike resistance.

Visual Sheep Scores
Description, extract and link to the Visual Sheep Scores resource.

Australian Sheep Breeding Values
Description of which ASBVs can be used to breed for flystrike resistance.

Fleece Rot scoring and selection
How to score fleece rot.

Breech Wrinkle scoring and selection
How to score breech wrinkle.

Dag scoring and selection
How to score dag.

Breech Cover scoring and selection
How to score breech cover.

 

Question and answer

For those who prefer a problem based approach to learning, answer the following questions.
Each of the questions below links further down the page to the answers.

Questions:

  1. Is it possible to breed for flystrike resistance and still improve productivity?
  2. What are the key steps in breeding to reduce flystrike susceptibility?
  3. What is the best (most accurate) and alternative ways to select rams for less wrinkle?
  4. What do visual sheep score assessments help you to do?
  5. What are ASBVs?
  6. Which ASBVs can be used to select for flystrike resistance?
  7. What are the 3 approaches you could take in breeding for plainer, more fly resistant sheep?
  8. The level of fleece rot varies with seasons, as such, should your fleece rot selection strategy be based on a particular score or on a % of the mob?
  9. How much wool growth is needed before selecting sheep on fleece rot?
  10. In winter rainfall areas, when is the best time to select for dag and how is it done?
  11. In summer rainfall areas, should dag scores be used to reduce fly strike risk?
  12. Breech cover can be used as a selection tool for reducing flystrike susceptibility. However, which other traits are more important to use first?

Answers:

You can also click on each question below to go to FlyBoss pages with related information.

1. Is it possible to breed for flystrike resistance and still improve productivity?

Yes. It is possible to select and breed your flock for increased flystrike resistance by focussing on the traits that increase the risk of breech strike (breech wrinkle and dag, and to a lesser extent breech cover and urine stain) and body strike (fleece rot).

Despite the slightly unfavourable relationship between fleece weight and wrinkle it is possible to maintain or improve productivity and breed plainer sheep at the same time. The industry’s experience in breeding for reduced fibre diameter, whilst increasing fleece weight is evidence that this is possible.

2. What are the key steps in breeding to reduce flystrike susceptibility?

1. Select rams with low wrinkle (and low dag, where dag is common) ASBVs.

2. Assess ewes for fleece rot, wrinkle, dag, urine stain and breech cover

3. Develop a joining strategy: breed the best to the best.

4. Assess your lambs and make a decision about mulesing and hogget classing

3. What is the best (most accurate) and alternative ways to select rams for less wrinkle?

Preferably your ram breeder can provide ASBVs for wrinkle.

a) If no ASBVs are available for wrinkle—ask the ram breeder to provide breech or body wrinkle scores for the rams you are inspecting.

b) If no wrinkle scores are available, and breech wrinkle has been removed by mulesingmake a preliminary assessment for wrinkle using neck wrinkle and body wrinkle. 

c) Consider changing to another ram source if your current ram breeder cannot supply rams that meet your needs.

4. What do visual sheep score assessments help you to do?

Visual scoring provides an assessment of the susceptibility of the flock for both breech and body strike.

With this information you can;

  • develop a breeding objective to improve traits in the future
  • develop a selection strategy to implement the breeding objective
  • develop a management strategy to control flystrike

5. What are ASBVs?

Sheep Genetics provides a single national language for genetic performance in the form of Australian Sheep Breeding Values (ASBVs), which are

  • calculated across-flock and, where appropriate, across-breeds
  • updated following the fortnightly analysis that takes account of all new information supplied by ram breeders
  • reported for a wide range of traits that are relevant to the various sectors of the sheep industry
  • used to compare the genetic potential of animals independent of the environment and location

6. Which ASBVs can be used to select for flystrike resistance?

  • Early Breech Wrinkle (EBWR), which will assist in the selection of rams that will breed progeny with less wrinkle.
  • Dag (Dag), to assist in the selection of sheep less prone to dag/scouring.
  • Breech cover (BCOV), to assist in selecting sheep with less wool on the breech.

7. What are the 3 approaches you could take in breeding for plainer, more fly resistant sheep?

  • Single trait selection for wrinkle;
  • Balanced selection for wrinkle and other traits within-flock;
  • Balanced selection combined with across-flock selection.

8. The level of fleece rot varies with seasons, as such, should your fleece rot selection strategy be based on a particular score or on a % of the mob?

The strategy should be to select against the worst X% of sheep in the flock, based on their fleece rot score. The value of X will depend on how much emphasis you want to put on this trait relative to other traits.

9. How much wool growth is needed before selecting sheep on fleece rot?

Sheep can be scored for fleece rot from 9 months of age. Scoring can be done at classing or shearing, provided there is a minimum of 6 months (or 40 mm) of wool growth to assess.

10. In winter rainfall areas, when is the best time to select for dag and how is it done?

The best time to assess dag score in a winter rainfall region is in the spring time prior to hogget shearing when at least 20% of the flock have an average score of 2 to 3 (click to go to diagram). Consider culling all score 5 sheep prior to mating. Mark score 4 and score 3 ewes and note the number in the flock so that an assessment of how many of these could be culled from the breeding flock can be made. 

11. In summer rainfall areas, should dag scores be used to reduce fly strike risk?

Yes, In the summer dominant rainfall environment few sheep get severe dags, but those that do so in the fly season are at extreme risk.  Therefore, it can be worthwhile to cull these sheep (same as culling sheep that actually get flystruck).

Generally, in environments where dag is sporadic or few sheep are affected, dag is better handled through management, rather than applying valuable selection pressure to dags, which could be used for other traits.

12. Breech cover can be used as a selection tool for reducing flystrike susceptibility. However, which other traits are more important to use first?

The importance of a bare breech in breech strike was investigated and it was found that it was less important than dags, urine stain and skin wrinkles. However it does play an important part as it can exacerbate the effect of wrinkles and dags.

 


Links to the other FlyBoss online learning topics

  1. Susceptibility
  2. Breeding and selection (you are currently on this page)
  3. Management
  4. Treatment
  5. FlyBoss Tools