Insect control and improving cattle health
Julia Herman, DVM, MS, DACVPM Beef Cattle Specialist Veterinarian, NCBA, a contractor to the Beef Checkoff | March 20, 2023
As spring planting winds down, cattle producers are moving on to other warm weather practices such as prepping cattle for summer pastures. A critical component to optimizing cattle productivity in the summer is parasite control, specifically ectoparasites or parasites that live on the outside of the host animal. Common ectoparasites include horn flies, face flies, ticks, and lice. All of these are challenging to control and can be detrimental to animal comfort and productivity. While controlling 100% or eliminating parasites is not a realistic strategy, preparing a year-long plan to control parasites’ negative effects on your cattle will prevent stress, improve performance, and reduce the risk of disease transmission.
Ectoparasite management varies by region with differences in climate, environmental conditions, host susceptibility, and farm/ranch management practices. To effectively treat or control parasites in the herd, it is important to know exactly which ones are a problem. This can be challenging at times, so it is important to have a resource team ready to assist. Working with your local veterinarian, extension agent, industry representatives, or local entomologists will help tailor a strategy to the specific operation. Your resource team can help in understanding the specific insects in your region, their effects on animal health, and utilizing multiple modalities of prevention and treatment is important to protecting your herd and minimizing negative consequences.
Types of insects
Flies and ticks are the most visible pest insect during the spring and summer months. There are a few general classes that are important to cattle health though this list is not all-inclusive.
- Horn flies are closely associated with cattle grazing in open pastures and rangeland. Adults tend to congregate on the back and shoulders of cattle or move to their underbelly during the heat of the day. Paul Kropp, National Account Manager for Central Life Sciences, explains, “Profit losses from a horn fly infestation begin when the population exceeds the economic threshold, which is just 200 flies per animal.” Horn fly attacks cause cattle to bunch which can lead to heat stress and decreased weight gain.
- Face flies are another common summer pest. They feed on the secretions from the eyes and nose of cattle. Due to proximity to the eyes, face flies also can feed on those tissues and cause irritation and damage to the eye itself.
- Stable flies are an important pest in cattle on pasture due to nesting and egg-laying in areas where hay and manure are mixed, such as old winter-feeding sites. They are also common in backgrounding or feedyard operations. Cattle will show stomping, tail switching, and bunching behavior to escape these flies.
- Ticks are blood-feeding arthropods than can infest multiple species including livestock, wildlife, and humans. Each species of tick has specific geographic regions where they are found and each has a unique life cycle that needs to be managed around. Hide damage can be caused by large numbers of ticks in addition to blood loss and reduced weight gain.
Animal health effects
Pest insects contribute to many direct and indirect losses for cattle herds. From blood loss to modifying behavior due to annoyance and attempted avoidance, cattle have added stress when dealing with these pests which can lead to reduction in feeding times and productivity. Kropp adds, “Fly infestations cause cattle to burn excess energy to combat the flies, interrupt grazing patterns, and cause cattle grouping. These can result in reduced weight gains, decreased milk production, and reduced calf weaning weights.” Anemia due to blood loss from severe infestations is especially harmful to calves and smaller animals.
In addition to being physical irritants to livestock, these insects can be vectors of infectious disease. For instance, face flies are the major vector of Moraxella bovis which is one cause of infectious bovine keratoconjunctivitis (commonly known as pinkeye). Ticks serve as vectors for anaplasmosis and bovine leukemia virus, both of which can have chronic health and welfare implications to individual animals and entire herds.
Prevention and treatment considerations
Preventive practices are paramount for the management of ectoparasites in conventional and organic operations. As discussed in the Checkoff-funded Beef Quality Assurance Program, animal husbandry and hygiene practices are an important step in raising healthy animals. Providing adequate nutrition to develop a strong immune system, managing pastures and working areas properly, optimizing sanitation practices to minimize predisposing conditions for parasite breeding grounds, and reducing stress all contribute to a successful response to integrated insect management.
To complement husbandry and environmental control measures for ectoparasites, there are many technologies on the market to assist with insect control. Choosing the correct product ingredient and method of administration 6for the intended parasite is critically important to the success of the control program.
- Insecticide ear tags (fly tags) are a useful tool in fly and tick control and easy to use. Timing of applying the tags is crucial as tags placed too early will lose effectiveness and need to be replaced by mid-summer. There are resistance issues developing in the horn fly population so it is also important to work with your veterinarian to ensure you are alternating the active ingredient in the fly tag every year to not promote resistance.
- Liquid pour-ons can be used effectively as long as the correct dose is applied for the weight of the animal. Work with your veterinarian to know what product is most effective for your operation.
- Feed-through fly control is a feed supplement that has either an insect growth regulator compound or larvicide that is passed undigested by the animal and deposited in the manure. Both products interfere in the life cycle and control fly populations. To increase efficacy, feeding these products about 30 days before flies emerge is recommended.
- Back rubbers, oilers, and dust bags could also be used depending on the facility setup. Setting these up next to the water trough or mineral tub increases the chance the cattle will use it.
- Fly predators use biological control instead of insecticides. These beneficial insects prey on pest insect larvae, laying eggs inside the host, eventually killing the pest insect. There are many commercially available fly predators.
- Fly traps are most useful in places in low-airflow areas such as barns or in areas of high organic matter buildup such as near working facilities.
Preventing resistance in the animal health realm applies to both antimicrobial and antiparasitic products. Anthelmintic (or dewormer) and insecticide resistance have become a real threat to prevention and control of parasites in livestock as decades of overuse have decreased the utility of certain classes of anthelmintics. It is important to have an insect control plan that utilizes management of the environment to prevent insect reproduction in addition to appropriate product use, if needed. As BQA emphasizes, proper dosing to bodyweight of the animal plays a role in effectiveness of the medication. While much focus is placed on withdrawal times for antibiotics, do not forget that many topical and injectable parasite treatments have withdrawal periods to adhere to. Another tip is to remove fly tags at the end of the season to help prevent resistance.
Integrated pest management allows cattle producers to evaluate multiple aspects of the operation minimize insect pests’ effects on their herd. Adapting a control program to the region and to specific pests will provide benefits to animal welfare and productivity. For further guidelines on herd health and animal product management, check out the BQA Field Guide at bqa.org.
This article was originally published in the June 2021 issue of NCBA National Cattlemen newsletter.
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