June Newsletter - External Parasites

Controlling External Parasites Helps Improve Cattle Profitability

Jeffery O. Hall, D.V.M., Ph.D.

Technical Services Veterinarian with Huvepharma

External parasites on cattle can hurt cattle production in multiple ways. Decreased growth rates and increased spread of disease both serve to not only decrease sale weights, but also cost ranchers in terms of increased animal deaths, veterinary costs, medicine expenses, and labor. The increased direct expenses and lost production costs the cattle industry several billion dollars a year in the US.

The most economic loss is generally attributed to biting (blood feeding) flies, Horn and Stable Flies. Horn flies can feed up to 40 times per day, while stable flies feed 1-2 times per day. Individual blood meals are very small, but large numbers of flies cause significant blood loss, especially with horn flies. Pain and discomfort from multiple biting flies can alter feeding behavior in cattle. Energy and other nutrients get diverted from growth and milk production to replacement of lost blood. In addition, cattle with flies tend to bunch up causing heat stress. Blood loss and decreased dry matter intake reduces growth rates, as well as milk production which decreases calf growth. Performance losses of 0.1 to 0.2 pounds per day can result in 20-25 pounds per animal in lost gain during a fly season.

In addition to lost growth, biting flies can also transmit diseases. Biting flies are associated with transmission of several diseases, including mastitis and anaplasmosis. Transmission of these disease organisms can result in increased culling, animal treatment costs, and death losses.

Non-biting flies, face flies and house flies, also cause losses in cattle operations. The abrasive, spongy mouthparts of face flies can cause damage to the surface of the eye, allowing pink eye organisms to attach and cause disease. Face and house flies feed on animal secretions, decomposing materials and feces. Feeding on these materials can allow mechanical transmission of disease organisms between animals and from waste to animals or feeds. Face flies are associated with transmission of pink eye and IBR in cattle. House flies can be vectors for the transmission of over a hundred different organisms. Because of pink eye disease alone, face flies are reported to cost the cattle industry over 750 million dollars in the US annually.

Control of flies in cattle operations often requires an integrated approach. The life cycle of fly species limits effectiveness of individual control methods, often producing less than optimal results. Stable, face, and house flies spend a lot of time off the animal on vegetation or structural surfaces. Adult flies generally live for only 2-4 weeks and fly eggs can take from 10 to 30+ days to develop into adults. And individual adult female flies can produce hundreds of eggs during their life.

Thus, only killing adult flies does nothing to prevent new generation development from eggs already laid. Similarly, control of fly egg and larval development with feed through insecticides, growth regulators, or biological control methods does not prevent adult females from laying eggs in areas away from these treated materials. Thus, combined control of adults, egg/larva development, and vegetation areas can synergistically decrease overall fly populations and allow for better health, production, and profitability in cattle operations. However, it should be emphasized that control plans should begin about 30 days prior to the expected beginning of fly season. This is necessary to get ahead of the start of a season’s first fly replication cycle and prevent increasing populations over time. By waiting until flies become a problem, it can take several weeks to significantly decrease fly numbers, as the next generation of eggs and larva are already available to replenish populations.

There are several biting and sucking lice that infest cattle. Their entire life cycle is on typically on the animal, as survival off the animal is limited. Small numbers of lice generally produce no visible adverse effects, but heavy infestations can cause general unthriftiness and poorer gain in cattle. Lice numbers are generally low during summer months but increase in cool/colder months when cattle are commonly in closer proximity. Lice are transferred by direct contact, animal to animal. Systemic antiparasitic treatments and fly control insecticides often are effective at limiting lice populations. However, a control treatment in the Fall, ahead of the cooler months, can help prevent heavier infestations during problem winter months.

Ticks are another external parasite of cattle that can impact health. Tick species are known to transmit viral, protozoal, and bacterial diseases. Heavy infestations can also cause significant blood loss. The most common disease transmitted by ticks in cattle is Anaplasmosis. However, a new tick species from Asia, the Asian long horned tick, and an associated tick born disease has entered the US and has been associated with transmission of Theileria which causes a severe anemia and deaths in cattle (currently only in the Eastern US). Predominant economic losses caused by ticks are a result of poorer growth rates, blood loss, animal deaths, and treatment of tick transmitted diseases.

Thus, good external parasite control is essential to optimize cattle health, productivity, and profitability. Formulating an external parasite PROGRAM, with the assistance of local veterinarians, extension agents, etc. is an important part of a progressive animal health plan for cattle. And, by implementing a plan prior to the external parasites becoming a problem, ranchers will achieve the best return on their investments.

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Spencer Ag Center can help you develop a parasite control program!

Pour Ons offered at SAC	Species Targeted
Cylence	Horn,& Face Flies, Biting & Suckling Lice
Inhibidor	Suckling & Chewing Lice, House, Stable, Horse, Horn, Deer, & Face Flies, Cattle ticks
StandGuard	Horn Flies, season long lice control
Vetrimec	Round worms, lungworms, grubs, suckling & biting lice, mange mites, horn flies
Intersect Gold	Horn, face, horse, stable, house, and black flies, lice & mosquitos
Other available pour-ons, sprays, and dewormers:	Evergreen, Sector, Synanthic, Clean-Up II, Safeguard, Dectomax, Cydectin

   Did you know that adding garlic to mineral supplements for cattle can be an effective natural method for fly control? Not only does garlic improve palatability, but when consumed it emits an odor through their breath and skin, deterring flies from landing and biting. Garlic-infused mineral salts, licks, or powder are readily available and can be mixed into existing mineral programs at Spencer Ag Center.

 IGR (Insect Growth Regulators) is another method for lowing insect populations.

Spencer Ag Center offers IGR boluses and feed products containing IGR. The chemicals in IGR interfere with the growth cycle of insects, preventing insects from growing to the adult

Solutions at Spencer Ag Center

stage. By feeding this product, insects who choose to lay their eggs in animal waste lower the reproductive cycle.

 Spencer Ag Center also carries products containing Clarifly and beef tubs for insect control. Ask your field marketer if interested in any of these options to protect your herd.