Production losses due to buffalo fly in cattle
Buffalo fly infestations are recognised as one of the most important animal health problems of beef cattle in Queensland. Each fly feeds up to 20 times a day by puncturing the skin and taking blood.
Welfare issues
The discomfort suffered by cattle infested with buffalo fly is obvious. Cattle welfare is important when considering fly treatment but it is also important to estimate economic losses to rationalise management decisions.Effect of buffalo fly infestation
Losses caused by buffalo fly infestation are mainly due to reduced feed intake of cattle. Individual cattle will vary in their response to buffalo fly infestation mainly due to individual variation in threshold levels in their immune system.
Numbers of buffalo flies
Most cattle can tolerate a small number of buffalo flies without a detectable loss in production. However, Australian research has shown that buffalo fly numbers of less than 100 per animal can have an effect on weight gain in cattle. Research on the related horn fly in North America showed a reduced growth rate with as few as 12 flies per animal. In dairy cattle, a threshold of 30 flies was needed before effects on production were detected.
Production effects
Infestations have many different effects on cattle. Unfortunately determining a production loss solely attributable to the effects of buffalo flies has often been difficult.
Reduction in weight gain
In Queensland beef cattle, a range of losses in production due to a moderate infestation of 200 buffalo flies has been recorded and the losses averaged 15 kg over a 100-day fly season.
Similar research in America on the related horn fly also recorded a range of losses in weight gains in cattle. For a moderate infestation of horn fly over a 100-day fly season, the reduction in weight gains of the cattle averaged 8 kg.
Reduction in weight gain of calves
Calves also experience a loss in weight gain due to reduced milk production in lactating cows. This has been measured in dairy cows and a moderate infestation of 200 flies reduced milk production by more than half a litre each day.
Lesions
Buffalo fly infestation can lead to the development of lesions in cattle. These lesions add to the discomfort of cattle and reduce the hide values. One Queensland study showed that about 40 per cent of steers and bullocks not treated for buffalo fly had buffalo fly related lesions compared to no lesions in a comparative group that had been treated for buffalo fly. This was repeated in the following year and about 60 per cent of the untreated cattle had lesions compared to less than 2 per cent of the cattle treated to control buffalo fly.
Generally there is no relationship between the number of flies on an animal and the presence or absence of lesions in cattle not treated for buffalo fly. This suggests that lesions may be due to individual sensitivity rather than related to the number of flies.
Most of the buffalo fly related lesions were around the eye or in the mid-neck region.
Pinkeye
One Queensland trial showed that nearly 30% of cattle not treated for buffalo fly control suffered from pinkeye during one season compared to no development of pinkeye in cattle that were treated for buffalo fly.