Fly control is one of the top issues facing dairy farmers. Summer brings warmer weather, longer days, pasture growth and grazing – things that we all look forward to during the long, cold and dark time of winter. The explosion of life in spring also brings with it the perennial and unwelcome problem of flies. Flies cause both irritation and serious economic losses to dairy farmers by spreading disease, feeding on animals (causing blood loss) and greatly decreasing productivity in grazing cattle by triggering them to crowd together and stop feeding. Pinkeye, mastitis and other diseases such as bovine leukosis are spread among cattle by the actions of flies feeding on them.
Economic losses are difficult to quantify but USDA has estimated that flies often cause a 5 percent to 20 percent loss of production for dairy cows. A 10 percent decrease in milk production is also the norm when flies are left unchecked.
Flies impact the entire operation on a multitude of levels. There is a reduction in milk production and farm worker productivity and an increase in the risk of complaints and legal action from the public.
Producers should consider a complete integrated pest management program that targets fly control across all areas on the dairy, including calf housing areas. By reducing flies near growing calves, producers can help increase calves’ comfort level, which can lead to decreased stress and more eating and growing.
With the new, lower required somatic cell count (SCC) legal limit looming in the very near future, every attempt to reduce animal stress and the development of new intramammary infections is warranted, especially during the hot summer months when fly populations are at their peak.
A survey performed at Louisiana State University showed that prevalence of mastitis in bred heifers was significantly lower in dairy herds that used some form of fly control for their lactating cows, dry cows and heifers compared with herds applying no fly control.
The greatest reductions were in numbers of Staphylococcus aureus and the environmental streptococci, both major mastitis pathogens in adult cows associated with elevations in SCC.
Now that we know the horn fly is not only responsible for teat lesions on heifers, but is indeed a vector in the transmission of mastitis-causing bacteria, such as S. aureus, from heifer to heifer, the next step is to effectively and economically stop them before they destroy your herd’s production potential.
Control options
Producers have several options to control fly populations and the irritation and disease they cause.
Sanitation: It sounds basic, but the preferred elimination method is to get rid of the habitat in which the larvae thrive. By removing the substances that allow them to grow and develop, producers can break the lifecycle of flies, thwarting subsequent fly populations.
Lactating dairy-approved insecticide ear tags: Insecticide-impregnated ear tags have gained momentum with the introduction of the new class of chemistry – endosulfan – that is cleared for fly control (and especially horn flies) in lactating dairy cows. Data show that ear tags (one in each ear) dramatically control flies for up to five months – long enough for the major summer fly infestation period in most dairies.
Additionally, ear tags with a higher level of diazinon insecticide (up to 40 percent) do an excellent job on both horn flies and face flies in non-lactating cows. The important factor here is that even the longer-lasting ear tags cost less that $2.00 per ear for season-long fly control.
Chemical pesticides and sprays: These can be used to gain immediate control of adult flies, though flies can quickly develop a tolerance. The strategic use of insecticidal pour-ons, dust products and spray-on products also helps the longevity and control level of ear tags. As a matter of fact, the combination of ear tags in conjunction with pour-on/spray-on/dust products decreased the incidence of new S. aureus by 83 percent during a six-month trial in heifers.
Feed-through larvicides: These prevent larvae harboring in cattle manure from developing into adult flies. Utilizing a feed-through larvicide is also gaining momentum in dairies due to its economics and ease of handling. An oral larvicide can be used in the manufacture of complete feeds, concentrates, protein supplements, mineral supplements and liquid feed supplements.
As an added ingredient in these feeds, it passes through the dairy animal’s digestive system and into the manure. It prevents the development of fly larvae in the manure of treated cattle.
Whether it is ear tags, pour-ons, sprays or oral larvicides, when combined with a proper integrated pest management program and proper sanitation, flies can be controlled and disease threats (i.e., mastitis) reduced.
And, with the proposed reduction in the SCC legal limit, and in light of the fact that milk buyers are imposing their own limits, it is imperative that dairymen utilize all possible means to prevent new cases of mastitis and their associated SCC. A simple fly control program can serve as an important adjunct to the dairyman’s plan of mastitis control and assist dairymen in lowering their bulk tank SCC and earn quality premiums for their product. PD
Skip French
Eastern Region Sales Manager
KMG Animal Health
sfrench@kmgchemicals.com
