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The Moo News

Newsletter of Penn Dutch Cow Care                                               May-June 2000


            ‘Tis the season.            Moisture + Manure = Flies

Pretty basic, really. Tips to keep flies down range from management changes to chemical sprays. I believe that drying agents are the best way to go, even when using chemical sprays. It is known that keeping moisture in manure to less than 40% will significantly decrease fly populations. Adding rock phosphate to the gutter will help do this as will increased fibrous material like straw, sawdust, chopped newspaper, etc. This will also increase the carbon to nitrogen ratio, which will help soil microorganisms decompose manure applied to land. Keeping youngstock well bedded will also help. Pens with “soup” for the animals to stand in are the most offensive. Hauling out manure from the gutter more than the typical once a week in the summer will reduce manure build-up and associated fly habitat..

            As for helping keep your animals comfortable, you can always use commercial sprays. If you are certified organic, you are limited to pyrethrum type sprays which give a knock down effect, with very little residual effectiveness. Flies will build-up resistance to any spray used repeatedly because of their quick reproducing abilities. Pyrethrums are allowed if used infrequently and with other management corrections. These cannot be “extended” (diluted) with diesel fuel on certified farms.

            The best true alternative to commercial sprays that I’ve ever witnessed is the use of pulverized limestone. This is liberally dusted onto the backs and sides of the cows. It helps keep the cow from showing moisture on the skin and thus she won’t attract flies.

I couldn’t believe how few flies were on this particular herd when I had just been in a barn dense with flies. Also good are the sticky lines that get reeled in, the Orkin fly zapper traps that the cows walk through, the tiny non-flying wasps which feed on fly eggs, and an herbal mix of essential oils that I’ve seen work nearly as well as pyrethrums. But no matter what, the key word in fly control in your barn environment is to keep things as DRY as possible.  Ventilation will also go along way in keeping flies at bay.

            Good luck this summer season!

For Bovinity Health, information on functional alternatives to antibiotics see:

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