There is plenty of research regarding the economic impact of flies on cattle. "The loss is always in the hundreds of million dollars range which is hard to comprehend," said Eldon Cole, a livestock specialist with University of Missouri Extension.
The biggest fly threat and dollar loss comes from the horn flies, followed by face fly, horse fly and the stable fly. Each of these flies irritate cattle in different ways such as sucking blood, transmitting disease and being a nuisance when cattle are grazing.
"The stable fly probably gets the least attention. However, they do suck blood and when present in even small numbers, as few as 5, they seem to drive cattle crazy," Cole said in a news release.
According to Texas A&M University researchers, the harm to animal health is especially noticeable when fly populations reach more than 20 per animal, and can significantly lower income for livestock producers. Research shows that heavy infestations of stable flies on beef cattle have reduced weight gain by 25% and, in dairy cattle, have decreased milk production by 10-to-20%.
Furthermore, a University of Nebraska study measured nearly a one-half pound a day decline in steer weight gains when stable flies were not controlled.
The Nebraska trial used a three-time a week insecticidal spray treatment to control the stable flies. Cole said this frequency of treatment would not be practical under most pasture management systems.
Farmers must first identify the stable fly in order to control it.
The stable fly looks like the house and horn fly, but is larger—roughly ¼ inch. Stable flies primarily attach the legs of livestock. A prime indicator of the presence of stable flies is when animals are stomping and kicking their legs. In some cases, stable flies will bunch together and attack one area, increasing the stress on the animal.
Stable fly control
Controlling flies is important to improve cattle comfort, but can prove difficult. "The usually reliable horn fly control methods do not work on stable flies," Cole explained. "Dust bags, ear tags and pour-ons do not reach the lower portion of the cattle's body where the stable flies feed. The oral larvacides do not control their breeding habits as they use old manure, straw and bedding for those purposes."
Kansas State studies have shown that an important egg laying area for stable flies is around big bale rings. Moving the rings regularly and not overfeeding can reduce the hay-manure buildup where the stable flies multiply.
"Observe your cattle regularly and if stable flies are suspected, take steps to reduce your cattle's discomfort and improve your profit margin," Cole said.
Source: University of Missouri Extension, Texas AgriLife Extension Service