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April 2010 Archive for Dairy Today Healthline

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Dairy Today Healthline

Control Fly Populations at Your Dairy

Apr 12, 2010

Dr. Larry Hawkins,

Senior Technical Services Veterinarian

Bayer HealthCare, Animal Health


House flies and stable flies are the most common flies found around livestock facilities. The two flies are very similar in size and appearance, except the housefly has a sponging mouth part and the stable fly has a piercing saber-like mouth part.


Both of these flies lay their eggs in moist, decaying organic matter, such as:

- the waste from the top of the silo
- decaying hay typically found where large hay bales are stored
- hay feeder rings
- piles of used bedding
- spilled feed along bunks or around the mill
- manure that accumulates under fences or along the edge of lagoons and runoff pits

Adults of both species can be found resting on the shady sides of posts, feed bunks, buildings, and vegetation when they are not on animals.


House flies use their sponging mouthparts to feed on liquefied organic matter. Although animal production losses due to house flies have not been documented, they are mechanical carriers of some diseases, including mastitis organism. Also, high numbers of flies around feed bunks can reduce animal feeding.


Stable flies use their piercing mouth part to suck blood primarily from the front legs of cattle. This causes cattle to bunch together in an effort to protect their legs from the painful bites.


Although data is lacking on dairy production losses, as few as three stable flies per leg have been documented to reduce average daily gain by 0.1 lb., and more severe infestations by 0.48 lb. in beef feedyards. Similar production losses would be expected when dairy animals are housed in similar environments.


As urban areas develop around livestock facilities, both houseflies and stable flies can become a nuisance to the neighbors. Occasionally, disgruntled neighbors have filed lawsuits resulting in fines to producers and/or closing of the facility.


Control both of these flies by:

- cleaning up the fly-breeding areas mentioned above;
- mowing weeds to eliminate some of the resting areas;
- using premise sprays on other resting areas to reduce adult populations. 

Because stable flies spend very little time on the animals, treatment of the animals may provide short-term relief from attack, but usually does not provide good control. For house flies, scatter baits and spot bait sprays can be used to supplement the premise sprays.


Although flies are a typical part of cattle operations, taking the appropriate steps to prevent and control these pests will help optimize cattle performance.

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