Q&A: Fly Control for Cattle

Fly control tips for healthier cattle and improved profits

Flies are much more than a nuisance. Their economic impact can reach deep into a cattleman’s pockets. Arnold Nagely, DVM, co-founder of Valley Vet Supply, offers answers to questions about fly control.

What’s the harm in flies near my cattle?

Excessive fly numbers affect cattle production in different ways -- none of them profitably. While cattle are fighting flies, they are not grazing and gaining the weight that they could be. Starting control measures before fly populations build usually yield better results. As with many challenges, prevention or early intervention is prudent.

What to use to keep flies off cows?

Timely spraying, cattle back rubs, and insecticide ear tags are among several methods utilized to stay ahead of major infestations. Fly control products have evolved over the years to offer producers with better protection for their cattle operations. Two of the greatest advancements I have  seen since beginning my food animal veterinary career, and before co-founding Valley Vet Supply in 1985, alongside fellow veterinarian Dr. Ray Shultz, include:

  • Insecticide application methods, which have evolved over the decades. Mist sprayers on ATVs are a popular insecticide delivery tool. Also, commonplace today are Fly Killer Kovers for mineral feeders, cattle rubs and even CO2-powered applicators such as the VetGun for use with insecticide VetCap capsules, offering a quick and convenient method to treat small- to medium-sized herds.
  • New insecticide chemicals have become available, particularly as ingredients in insecticide ear tags and in the capsules for CO2-powered applicators.
  • Warm weather provides the perfect environment for a rapid increase in fly populations. Of the different species of flies affecting cattle operations from herd health to operational profitability, there are a number of fly control methods available to help control them and dramatically limit profit loss. Let’s review the different fly species and their economic impact, according to data provided by Bayer Animal Health, along with recommended action to take for effective control methods.

    Which fly species are the greatest risk to cattle?

    Face flies

    Face flies can cause reduced grazing and weight loss. In fact, it takes only 12 flies on a cow’s face to potentially reduce grazing time by as much as an hour a day. Face flies also transmit the pinkeye-causing bacteria known as Moraxella bovis, plummeting profit by as much as $12 per hundredweight, compared to healthy calves sold without pinkeye.

    Pinkeye is a costly problem in cattle, to say nothing of the nuisance and inconvenience of continually treating new cases, just when the operator needs to be in the field or attending to other responsibilities. We know the causative agent for pinkeye is likely a Moraxella bacteria, and that tall seed heads can scratch the animal’s eyes making them vulnerable to bacterial invasion. But it’s the dern face flies that spread the disease from animal-to-animal, and sometimes herd-to-herd across the fence.

    Watch for: Feeds on: On-animal prevention:
    Flies on the faces of livestock, especially around the eyes and muzzle Saliva, tears, nasal mucus

    Insecticide ear tags, pour-on, sprays and dusts

    Horn flies

    U.S. livestock producers lose $1 billion annually because of the horn fly, due to decreased feed intake, weight loss and diminished milk production. Even more, horn flies also are linked to summer mastitis outbreaks. A single horn fly can take a blood meal from a calf up to 30 times a day, and the impact on rate of gain for yearlings is colossal, reducing yearling weights by 18 %. Compared to yearling cattle experiencing heavy horn fly infestations, those with horn fly protection had anywhere from 15 to 50 pounds greater weight-gain advantage. Additionally, calf weaning weights were 10 to 15 pounds higher when horn flies were controlled on mother cows.

    Watch for: Feeds on: On-animal prevention:
    Flies on the backs, sides, shoulders and belly region of cattle, tail switching, visible irritation, bunching together with the herd blood (cattle) Insecticide ear tags, pour-on, sprays and dusts, plus larvicide feed-throughs

    House flies

    The house fly causes aggravation in cattle, pen avoidance and reduced feed intake. Like the horn fly, the common house fly also transmits mastitis-causing bacteria.

    Watch for: Feeds on: On-animal prevention: Environmental prevention:
    Constant cattle movement, bunching, tail switching, flies on structures and animals near feed Manure, leftover feed, waste, sweat, tears Insecticide ear tags, pour-on, sprays and dusts, plus larvicide feed-throughs Facility insecticide sprays, baits and dusts

    Stable flies

    Costing producers $2.2 million every year, stable flies can cause blood loss, reduced milk production by up to 40%, and decreased weight gain by as much as .48 pounds per day.A common tell-tale sign of stable fly invasion, is grass cattle huddled in the corner of the pasture, rather than out grazing. Or they may take refuge in the pond to keep those flies off their legs and bellies. In addition to reaping havoc with pasture cattle, stable flies also can be a real menace to show calves around the barn.

    Watch for: Feeds on: On-animal prevention: Environmental prevention:
    Flies on lower legs of cattle, stomping or bunching, constant cattle movement Blood (cattle) Insecticide ear tags, pour-on, sprays and dusts, plus larvicide feed-throughs Facility insecticide sprays, baits and dusts

    What else do you recommend to control flies on cattle?

    In addition to fly control methods mentioned above, try not to underestimate the value of regular cleaning around your barn and property. With some quick cleaning every day or so, you can minimize the fly egg production cycle by removing common fly breeding areas (flies are most drawn to moist areas, such as manure and excess plant material, like old, unused sileage.) Keep these tips in mind:

  • Tidy barns and lots, as well as feed bunks.
  • Clean barns and lots often, weekly if possible, spreading the manure so it dries.
  • Remove unused or wet spoiled feed.
  • Spread out or remove uneaten hay to dry quickly.
  • Use fly predators, which are cocoon-conquering bugs that kill immature flies.
  • Prohibit the fly population through pasture management.
  • Help manage moist, wet areas of pastures through drainage where practical.
  • Keep overburden of plant residue at a minimum by controlling and cutting back excessive weeds and plant growth.
  • Use larvicide feed-throughs in the mineral, preferably beginning before turn-out.
  • It is crucial for producers to leverage effective insecticides and fly control methods to help keep cattle healthy. Begin methods of fly control early, and practice insecticide rotation, for the best results against emerging fly populations.

    Shop fly control options, shipped fast to your farm from veterinarian-founded Valley Vet Supply.

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