YC.com: Dewormer

During the warm summer months, grazing cattle are often subject to harassment by flying pests. In terms of economic loss, cattle producers are familiar with profit-robbing maladies such as Anaplasmosis and Bovine Respiratory Disease. Both result in estimated annual losses of up to $60 million and over $1 billion, respectively. Surprisingly though, neither represent the greatest economic threat to the cattle industry. The horn fly is the most pervasive and most costly external parasite affecting North American cattle. While the face fly, housefly, stable fly and horn fly all negatively impact grazing cattle, the horn fly is far and away the most damaging.

Horn flies are blood feeders and use their proboscis, a cutting and digging mechanism, to deliver a painful bite. Adult horn flies have a ten to twenty day life cycle, mate while on livestock, leave their hosts to lay eggs and during a lifetime, a single female horn fly may lay up to 500 eggs in fresh manure. The start of the horn fly “season” begins around March 1st in parts of Texas and the deep South and as late as May 15th in the Northern Plains and usually lasts until the first frost. Meanwhile, populations are usually at a peak in early summer, and another peak may be seen in fall depending on moisture. When not held in check, up to 4,000 horn flies may be seen on a single animal. This can be devastating. Data suggest that only 200 flies per animal represent an economic threshold.

When grazing cattle are tormented by horn flies, less time spent grazing is often the outcome. It stands to reason that if a lactating cow spends less time grazing, her body condition and the weaning weight of her calf may be decreased. Likewise, rate of weight gain in grazing calves and yearlings may be depressed when horn flies are a problem.

Through annoyance and irritation, horn flies may increase energy requirement, decrease feed efficiency, and lower conception rates. Moreover, an animal’s physiological responses may include elevated body temperature, increased heart rate, and increased water intake. In summation, horn flies cause cattle to expend energy either trying to banish the flies themselves or in an effort to soothe the pain and irritation that they cause. Such energy expenditures come at the expense of important economic parameters such as growth, milk production and reproductive efficiency. It is estimated horn fly damage may carry a $40 loss per cow.

Fortunately, cattle producers have many effective options to help control horn flies and reduce the threat of related economic losses. Insecticide ear tags, back rubbers treated with an insecticide, premise sprays, and feed thru products such as oral larvicide and insect growth regulators are currently available to producers as means to control fly populations. Many of these methods utilize organophosphates, and evidence exists which suggests that flies are becoming somewhat resistant to certain compounds. Thus, it is recommended that a fly control strategy be comprised of at these two different methods. While each method has its pros and cons in terms of convenience, safety, cost, and effectiveness, a suitable fly control strategy should more than pay for itself with increased weight gains, body condition and overall performance.

Using a feed thru as part of a fly control strategy has benefits beyond just fly control. Feed thru insecticides are often incorporated into feeds, liquid supplements, tubs, blocks or pasture mineral mixtures. If producers elect to use a feed or supplement and “hand feed” daily, cattle are readily available for observation and many times become accustomed to vehicles, feeding equipment and people. These benefits are in addition to the extra nutrition provided by the feed or supplement. Pasture mineral mixtures with feed thru insecticides can also be an effective part of a fly control program. In addition to fly control, a complete vitamin-mineral mixture with a feed thru insecticide provides nutrients that are necessary for grazing cattle to get the most from forages and pastures.

Since we are right in the middle of the peak season for horn flies, consider a fly control strategy utilizing two of the aforementioned methods. Cattle should be more profitable when less energy is spent fighting flies and more energy is utilized to improve productivity. ©