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Beyond the Bale : June 2016
38 ON FARM BREECH STRIKE R&D UPDATE Breech strike R&D continues to be the highest priority for AWI’s on-farm R&D and extension portfolio. It centres on breeding for breech strike resistance, more recently bacteria and odours; breech modification to reduce breech wrinkle, urine stain, dags and breech wool cover; new fly chemical control products; and improved pain relief options. BREEDING While dags, urine stain, wrinkle and wool cover are key breech strike risk factors, some sheep that have high dag, stain, wrinkle and wool cover do not get struck and some sheep with low dag, stain, wrinkle and cover do get struck. It is suspected that the “as yet unknown” risk factors are differences in odour and bacteria between sheep. Studies continue into determining what it is that is attracting female blowflies (Lucilia cuprina) to some sheep, and how and why its larvae parasitise sheep while other larvae do not. A breakthrough in the odour and bacteria work is proving elusive despite considerable effort. As sniffer dogs were still able to differentiate between old wool samples grown from resistant and susceptible sheep, it was thought that this would also be the case for gravid flies. However it has recently been found that fresh wool samples are needed. Using gas chromatography technology the number of likely odour causing chemicals compounds are being reduced. Then an electro-antennagram that measures the gravid fly’s response to each compound is used to identify the odour chemicals that attract the flies. The goal is to be able to select and breed sheep that don’t emit the attractant odours along with the known key breech traits, and therefore reduce their exposure to and risk of breech strike. BREEDING VALUES In late 2009, MERINOSELECT released the first breeding values for the key breech traits. Since then breeders have been able to add these traits to their selection criteria and better manage the antagonistic traits with fleece weight such as wrinkle, fat and muscle. Increasingly there are high productivity sires with improving breech strike resistant traits – se e table 1 opposite. Dags continue to be the most difficult breach trait to make progress. CHEMICAL CONTROL Use of increased breech strike prevention chemicals along with crutching and breeding is the main way woolgrowers have been able to move to a non-mules operation. Chemical prevention is very important for all woolgrowers in high dag regions and while cyromazine and dicyclanil are very effective in controlling breech strike, with increased use and reliance, there are increased risks that resistance to these products will emerge. AWI is co-funding projects with the University of Melbourne and CSIRO Brisbane to better understand the fly genome and the potential for new and better targeted, long term effective chemical control compounds. Greater understanding of the genes that are unique to and active in the gravid fly and larval stages of the Lucilia cuprina species could uncover new control methods and compounds. SKINTRACTION® The Australian Pesticides and Veterinary Medicines Authority (APVMA) has registered the SkinTraction® intradermal, but there have been a few trials where the product moving into underlying tissues, has led to very tight label use requirements which have stalled commercialisation. Discussions continue between AWI and the Directors of Cobbett Technologies Pty Ltd which owns SkinTraction®. LIQUID NITROGEN Steinfort Agvet Pty Ltd, with co-funding from AWI, is investigating ways to improve the consistency of application of liquid nitrogen to raised folds of breech and tail skin (to reduce breech and tail wrinkle dags and wool cover), increase the hourly rate of the application, and get the process to a state where it is ready for commercialisation. In trials to date, significant wrinkle and wool cover reduction has occurred resulting in nearly all sheep well under the targets of Pictured are Department of Agriculture and Food (WA) senior research officer Dr Johan Greeff (left) and senior veterinary officer Dr Dieter Palmer with Dr Shimin Liu, University of Western Australia, and Chinese visiting scholar Dr Zhong Quan Zhao discussing the importance of conducting faeces testing for long term reduction in worm egg count along with reducing dags, in the department’s South Perth animal laboratories.
In the Shops - September 2016