Control lice in the winter and horn flies in the summer.
Lice puncture the skin of host animals to take their meals. Biting lice scrape and irritate the animal’s skin. Parasites cost you money. Drivers of economic loss associated with them include reduced average daily gain and weaning weights, decreased feed efficiency and increased susceptibility to disease.
Infestations of biting and sucking lice have been associated with reduced weight gains and general unthriftiness of cattle. The economic impact of these small insects has been very difficult to assess. However, it appears that an average of 10 insects or more per square inch will have a significant effect.
Moderate-to-heavy infestations add to the impact of cold weather, shipping stress, inadequate nutrition, harm from internal parasites or disease. The interaction between low levels of both lice and intestinal nematodes can reduce weight gains by more than 8 percent. The energy that lice steal, coupled with other factors, can have a severe impact on animal health. This impact shows itself in various ways. It can be anemia, slow recovery from diseases, poor gains or general unthriftiness.
Lice are primarily spread from animal to animal. Lice can arrive on new cattle. Any time you bring in new cattle, you need to be persistent about treating them.
It is best to assume that all purchased animals are infested. They should be isolated from the existing animals until their full course of treatment is completed. Cross-fence contact can be enough for spread of these insects, especially during the winter when louse burdens are greatest.
Lice spend their lives on the host animal. Sucking lice typically die within a few hours of being removed from the host. Biting lice, can live up to a few days off the host—under ideal conditions.
A high-energy diet seems to reduce the effects of cattle lice on weight gains, perhaps because lice populations decline on better-fed cattle, a sound feeding program and high energy ration serves as the foundation of a louse control program.
Lice interventions include insecticide sprays, pour-ons and dust. As soon as summer comes, the lice begin to disappear and horn flies roll in.
A few horn flies can reduce performance substantially; these blood feeders can take 20 to 30 meals per day. An individual horn fly only consumes 1.5 mg of blood per meal. However, when there are a large number of flies, the blood loss can be substantial. While it is not feasible to eliminate horn flies, it is well worth it to reduce horn fly pressure. Controlling horn flies on calves will likely result in calves that are 25 to 50 pounds heavier at weaning. Controlling horn flies on cows will likely result in calves being 10 to 15 pounds heavier at weaning.
The economic threshold of horn flies is about 200 per animal. This is best evaluated early in the morning, with still air. The method used for estimates is to count the number of flies on an animal’s side. If there are more than 100 flies, there will be a positive response to controlling horn flies.
Horn flies are relatively weak fliers. They spend most of their time on the animals. Females will leave hosts only to deposit eggs in fresh manure or to seek other hosts. Because horn files must lay their eggs in manure, they are susceptible to feed-through pesticides that have activity in the manure. For pasture cattle, the product of choice is Altosid. Altosid is standard in MFA mineral in a wide range of MFA mineral products. Visit with your local MFA feed representative to find one that fits your needs.
Horn flies reduce animal performance because cattle predated by horn flies will have disrupted and decreased grazing. The cattle will spend more energy on moving, rubbing, tail switching or other activities to reduce fly irritation. The skin irritation from numerous bites may result in open wounds, which can increase the risk of secondary infections. Infected lesions may result in reduced hide value. Additionally, horn flies are suspected of transmission of anaplasmosis, anthrax and other diseases.
The best fly is one that never gets to your herd. Prevention pays.