Control of biting flies on beef steers: effect on performance in pasture and feedlot

A mixture of 0.5% p,p’methoxy-DDT (methoxychlor), 0.5% carbaryl, 0.1% pyrethrins and 1% piperonyl butoxide was tested in 1969 and 1970 for the control of Haematobia irritans (L.) and Tabanids on beef steers in Mississippi. The mixture was applied as sprays from 30th April onward at weekly intervals to a group of 12 steers in a pasture in each year, and the flies on the treated and on 12 untreated steers in a separate pasture were counted on the days before and after each application. The steers were treated for 16 weeks in 1969 and for 20 weeks in 1970. The mean counts the day before application indicated that the numbers of H. irritans on the treated animals were reduced by 100% in 1969 and 98% in 1970 compared with the untreated animals and the numbers of Tabanids by 38 and 54%, respectively. Treated steers gained on average 0.20 lb/day more than untreated steers in 1969 and 0.23 lb/day more in 1970. Observations on some of the steers during the subsequent fattening period in feedlots showed that the treated steers averaged higher daily weight-gains and required less food for each pound of weight gain than the untreated steers, though the differences were not significant.