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An innovation hub for the woolgrowers of Australia

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23.10.2020 Source: AWEX
AWEX EMI 1219 +102
Micron 17 1820n +88
Micron 18 1615 +83
Micron 19 1390 +86
Micron 20 1283 +123
Micron 21 1204 +59
Micron 22 1198n +112
Micron 26 886n +138
Micron 28 673 +158
Micron 30 533 +94
Micron 32 331n -370
MCar 816 +62
Breeding for Breech Strike Resistance
Breeding naturally resistant sheep is the long term, sustainable solution to reducing the risk of breech strike.

Results from genetic research indicate breeding for enhanced flystrike resistance without a high reliance on chemical control and ensuring productivity is high can be successful but it will take a considerable amount of time to achieve, particularly for super fine and fine wool sheep and sheep in high dag environments.

An integrated approach to reducing the risk of breech strike is required to successfully move away from mulesing. These practises include:

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Short timely lambing periods

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Breeding for low wrinkle, low dags, low urine stain and low breech wool cover

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Proactive marketing of wool and surplus livestock sales

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  • Worm control, drenching and paddocking
  • Fly control including chemical treatments

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  • Timely annual shearing and crutching
  • Accelerated shearing and crutching


Sheep most at risk of breech strike:

  • Have higher degrees of skin wrinkle and/or wool cover in the breech region and/or;
  • Are more susceptible to dag accumulation and urine staining of wool

Recent trial results indicate there are good prospects for reducing the incidence of flystrike over the longer term by breeding for key flystrike resistant traits, i.e. reducing breech wrinkle, breech wool cover, dags and urine stain.

Australian Sheep Breeding Values (ASBVs) for the key traits related to flystrike (Breech Wrinkle, Breech Cover and Dag) are now available for many sires.

The three-and-a-half year Merino breeding cycle (average generation interval) and the need to maintain sheep productivity, health and welfare both slow the rate of progress towards a naturally flystrike resistant flock.

Breeding for lower wrinkle often leads to decreased fleece weights, but sheep that are relatively high in fleece weight and low in wrinkle have been identified and the industry is selecting and breeding from these to ensure they maintain and/or increase productivity whilst decreasing wrinkle in their flocks.

Tools for Breeding Flystrike Resistant Sheep

Our genetic research into natural flystrike resistance and Sire Evaluation led to the development of three new tools for sheep breeders. The Australian Sheep Breeding Values for Breech Wrinkle, Breech Cover and Dag were released in late 2009.

Sheep breeders can use breech trait scoring charts to select sheep with higher natural resistance to flystrike. The scores provide a consistent language for scoring sheep traits across the country.

Education and extension programs are readily available to woolgrowers wanting to more efficiently select and breed naturally flystrike resistant, profitable sheep, to reduce the reliance on mulesing, and for managing the risk of breech strike.

Planning for a non-mulesed Merino Enterprise

We developed this report to uncover the key learnings from a number of wool-growing enterprises that have moved to a non-mulesed enterprise. It is intended to assist other woolgrowers in their consideration and planning to also move to a non-mulesed Merino enterprise.

Planning for a non-mulesed Merino enterprise (March 2018) (PDF 589Kb)

Further Information
CSIRO Armidale Breech Strike Resistance Newsletters

Click the following links to download presentations on research into breech strike genetics.

DAWFA Mt Barker Breech Strike Resistance Newsletter

Click the following links to download presentations on research into breeding for breech strike resistance.

Breeding for breech strike resistance

Click the following links to download presentations on research into breeding for breech strike resistance:

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