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    Rights: © Copyright 2016 University of Waikato. All Rights Reserved.
    Published 21 July 2010, Updated 15 March 2018 Referencing Hub media

    When dags form on a sheep’s backside, it makes them susceptible to flystrike, which occurs when blowflies lay maggots in their fleece. Dr David Scobie describes the problem flystrike causes and how it can be treated.

    Note: Of the nearly 2000 Wiltshire lambs weaned during 13 years of research, there was only one case of flystrike.


    Dr David Scobie, AgResearch

    Dags are just an accumulation of faeces, and when you have the backside of a sheep and then there is wool hanging around it, you will get faeces coming out and they touch onto the wool – and it is actually surprisingly hard to get faeces to stick to wool, but once they do, then the next lot will actually find it really easy to stick to the other faeces, and very rapidly you will get these things growing on the staples of wool, we call those dags.

    A mixture of the faecal deposits and perhaps also the urine that is coming out close to there as well, mix in a bit of wetness, and it’s like wearing nappies for too long. The skin starts to get a bit reactive and starts to release a bit of serum or loosens the skin up a lot and then blowflies are attracted to that, and they will lay maggots on the faeces and then in the wool, and those maggots will attack the sheep's skin and they can eventually kill it.

    There is a number of ways of treating flystrike, and you can just take a set of shears and take the wool off that has the maggots in it and that will dry out the skin very quickly. Another way is to actually just leave the wool there and then squirt loads of chemical that will kill the maggots. There has been some debate over which is the best way to do that, and if you cut the wool off and the skin has been chewed away at by these maggots, it will expose it to the sunlight and you can get a bit of sunburn, and it takes a while for that skin to heal. The jury is still out on which is the best way to treat those animals.

    Dr Clive Dalton, Woolshed 1
    Natural Science Image Library
    Miffy Wickham
    Photographer: G. R. ‘Dick’ Roberts © NSIL
    Moseley Wool
    Lawrence Wright