Nuisance or Detriment? The impact of flies on cattle performance

Fly control is of major importance for overall animal health, comfort, and ultimately the producer’s bottom line. As we approach the upcoming fly season it is time to start looking at how effective we are at keeping those pesky flies away. If last year’s program did not work, we should evaluate new methods of control.

Though there are a variety of flies out there, three major species seem to affect livestock the most. Horn flies, face flies, and stable flies each affect livestock in different ways.

Horn flies
Horn flies alone account for approximately $1 billion in production losses annually. Female horn flies lay their eggs in fresh manure, making them prominent in feedlots, dairies, and open pastures. The stress and annoyance of these blood-sucking flies cause decreased milk production, lowered weaning weights by up to 15%, and reduced daily gain reductions of18% in cattle that have not been treated. The impact threshold level is 200 flies per animal. While that may seem like a lot,  remember that a fly is only 3-5 mm long. Two hundred flies cover 8 square  centimeters, which is not even enough to cover the area of a wide-mouth jar lid! In addition to causing production losses, horn flies facilitate the spread of summer mastitis.

Face flies
Face flies are non-blood-sucking flies that feed on animal secretions and manure. They congregate around the eyes and muzzle of cattle and carry a bacterin called Moraxella bovis which is a leading cause of pinkeye and bovine keratoconjunctivitis in cattle.

Stable flies
Stable flies become more of a problem in feedlots, dairies, and other confinement feeding areas. Female stable flies lay their eggs in fermenting organic matter such as old hay rings, bunk lines, and other places cattle eat or drink. Their bite is extremely painful and will cause animals to stomp, crowd together, and stand in water to avoid getting bit. The impact threshold for stable flies is quite small at 5 flies per leg. Stable flies cause production losses similar to those of the horn fly, and daily gain losses in untreated animals have been recorded up to 0.5 lb versus treated cattle.

Control methods
A variety of control methods are available for producers, each has pros and cons. In many cases, a rotation and/or combination of methods provide the best results.

  • Manual oilers and dust bags provide good protection from flies; however, cattle must be forced to walk under or through them consistently to provide the needed solution on a routine basis.
  • Insecticide impregnated ear tags will often provide lengthy protection from flies with little input. Resistance has been observed across all classes of insecticide, therefore it is recommended that producers rotate classes on an annual basis. It is also important that both cows and calves are tagged as tagging one or the other will not protect both animals.
  • Sprays and pour-ons provide anywhere from 7-21 days of control and may be applied in the pasture (depending on the docility of cattle). These must be reapplied throughout the fly season.
  • Oral larvicides or insect growth regulators (IGRs) prevent eggs from maturing into adult flies. They can be added to a salt and/or mineral mix and provided free-choice. They must, however, be consumed regularly. It has been reported that flies will travel up to 10 miles. For best results, it is important that your neighbors also be providing some sort of fly control.

A new, natural fly control method has been introduced in recent years. It is none other than…GARLIC! Garlic powder provided at 2% of a salt/mineral mix reduced flies by 50% on cattle in Saskatchewan. For the past few years, it has found relative success as a fly control mechanism in the Midwest.  While the mechanism is unknown, think of it as sitting next to someone who has just consumed a large amount of garlic. If you don’t want to be around them, why would the flies?

The key to success with any fly control method is to get the product in/on the animal early. Flies typically appear in early May and remain until at least late August. You will see more success controlling flies if you start acting in April before they arrive. It is important to consider the length of protection provided by each method to ensure the cattle are covered for the entire fly season.

For any questions on your fly control methods and/or about adding an IGR or garlic to your mineral package please contact your local Sioux Nation representative.