Impact of horse flies (Diptera: Tabanidae) on beef cattle

In studies in Oklahoma in 1982 and 1983, yearling Hereford heifers exposed for 84 days to attacks by adults of Tabanus abactor, T. atratus, T. equalis, T. mularis, T. subsimilis and T. sulcifrons with an average of 90 and 66 tabanids per animal per day, respectively, gained 0.08 and 0.10 kg per animal per day less than heifers protected from tabanids. The average daily weight gain of heifers exposed to tabanids was 0.09 kg per animal per day less than those not so exposed. Exposed heifers were 16.9% less efficient in feed utilization than protected heifers. The greatest impact of tabanids occurred during the high attack rates at the end of the first and throughout the second of the three 28-day periods of the study. The potential total loss each year in weight gain in heifers exposed to tabanids for 84 days was >$10.00 per head.