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How It Works

Horn flies spend their time biting cattle’s backs and midlines, spreading down their sides. This location is tough for cattle to reach, leading to the irritation that causes cattle to go off feed. To stop this problem, it is easier to attack flies where they lay their eggs and prevent the emergence of future populations.

Altosid ® IGR is an insect growth regulator (IGR) that passes through the animal and into the manure, where horn flies lay their eggs. It breaks the horn fly life cycle, preventing pupae from developing into biting adult flies. There’s no need to round up or handle cattle because the animals spread the horn fly control as they graze, placing it in the exact location where horn flies lay their eggs.

Life-cycle of a fly diagram

Horn Fly Life Cycle (see image above)

  1. Altosid ® IGR is ingested with the cattle’s mineral or feed. As they graze, cattle disperse the IGR via their manure.
  2. Adult horn flies live 2-4 weeks, taking 20-40 blood meals per day.
  3. Female flies leave the animal for a few seconds to lay eggs in fresh manure less than 5 minutes old.
  4. In 1-2 days, eggs hatch into larvae.
  5. In 3-5 days, the horn fly larvae molt into pupae.
  6. Pupae molt into adults in 6-8 days. Altosid ® IGR breaks the horn fly life cycle here before that happens, preventing adults from emerging.

Control Resistant Flies

An effective fly control program keeps horn fly levels at less than 200 flies per animal. Altosid ® IGR controls horn flies resistant to the organophosphates and pyrethroids commonly used in conventional cattle fly control products. In more than 40 years of use, there have been no known cases of insect resistance to Altosid ® IGR.
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Q & A

A. Horn flies are the number one economic ectoparasite 1 in North American cattle production, causing an estimated $1 billion loss annually. Compare this to the estimated loss due to bovine respiratory disease at $600 million or pinkeye at $100 million.

A. Horn flies are an ectoparasite of cattle and tend to stay on the backs and sides of animals throughout the day. Despite their name, horn flies do not congregate on the horn and head area. Horn flies are about half the size of the common house fly and lay eggs exclusively in fresh manure.

A. Horn flies cause cattle stress. Under stress, cattle will not feed as freely and may move to areas in or near water to escape fly pressure. A moderate horn fly population of 350 flies per animal would cause 12,250 bites and suck 4.14 oz. of blood per day, amounting to 5.82 gallons of blood loss per 180-day season. Typical weight loss is estimated at 15 to 50 pounds per yearling. Also, a 10- to 15-pound weaning weight advantage results when good horn fly control is used. 2

A. The easiest way to control horn flies is to use an insect growth regulator (IGR) which allows you to add horn fly control right in your feed or minerals, letting cattle do the work. This is much less labor intensive than other options such as dust bags and back rubbers.

A. University research indicates the economic threshold for horn flies is 200 per animal and, for dairy cattle, may be as low as 50 flies per animal.

A. The cost per animal will vary and can be measured on a return-on-investment (ROI) basis. For ear tags, you should also consider the cost of labor to determine the real cost per animal.

1 Byford, R.L., Craig, M.E., Crosby, B.L., A Review of Ectoparasites and Their Effect on Cattle Production, J. Anim. Sci., 1992, 70:597-602.
2 NebGuide, University of Nebraska Cooperative Extension Service.

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