Robyn Stewart
Summer in Georgia provides some of the best grazing opportunity for our cattle operations, but also presents the challenge of external parasites. External parasites can limit productivity and affect a producer’s bottom line if not managed appropriately. Animals with a high external parasite load will lose weight, reduce meat/milk production, transmit diseases, reduce feed efficiency, and have reduced value of hide and hair. With current cattle prices, producers may be trying to find ways to save money while maintaining their herd. When making decisions for your parasite program, consider the economic threshold for each pest. The economic threshold is the point at which the loss from the parasite is equal to the cost of treatment, and will vary for different parasites.
There are many external pests in Georgia, including many varieties of flies (hornflies, blowflies, face flies) and other sucking insects like lice, mites, and ticks. While I can’t cover all of these pests today, I do want to use the example of the horn fly to explain why the economics of parasite control are so important. One of the most economically important parasites in beef cattle are horn flies. These flies interrupt cattle from grazing and consume up to 1 pint of blood per day—leading to 15-30% less weight gain over an 80-day period. If not treated, this 15% reduction in daily gain can cost the producer $68/head income loss. For the beef industry, horn fly losses translate to nearly $1 billion per year. The economic threshold for horn flies is 250 flies per side—if you have parasites number over this threshold, treating your stock should generate a positive return on your investment.
As with all pests, we use an Integrated Pest Management approach. Insect breeding occurs most often in areas with poor sanitary conditions. For most Lincoln County producers, sanitary procedures will include dragging or mowing pastures to spread and eliminate manure piles. Pasture rotation is also a great way to give manure time to dry and decompose. Wet manure and feed can support external parasite breeding and should be avoided. Biological control includes beneficial and predatory insects that can help with parasite control, including fire ants, soldier fly maggots, dung beetles, and parasitic wasps. Chemical control is typically necessary once the economic threshold has been met. Control options include ear tags, sprays, pour-ons, injections, feed products, bolus, dust bags, and more. Each treatment has its own instructions, dosing, and interval you need to follow in order for it to be effective. Make sure to consider your handling facility/capability, frequency of treatment, efficacy of the method you choose, and withdrawal times when selecting the best insecticide for your herd.
While cattle producers are facing some hard times and the expense of parasite control may not be a priority, managing critical pests is essential to keeping a healthy, profitable herd. If you need assistance determining if your herd is above the threshold or if you need help selecting the right insecticide form and product for use in your herd, please reach out to us at uge3181@uga.edu or 706-359-3233.
