Effect of insecticide treatment for control of buffalo fly on weight gains of steers in coastal central Queensland

Abstract

The effect of controlling buffalo fly, Haematobia irritans exiua, upon liveweight gain of cattle in coastal central Queensland was assessed during 3 experiments in the fly-activity seasons of 1976- 77, 1977-78 and 1978-79. In each experiment, the weight gains of 2 herds of growing steers that carried natural buffalo fly infestations were compared with those of 2 similar herds that were treated with insecticide to reduce fly numbers. Insecticide was applied as a spray during the first 2 experiments and portion of the third; chemically impregnated eartags were used thereafter. Average fly burdens per animal on untreated cattle were 324, 470 and 172 in successive expriments. Based on counts made prior to each insecticide treatment, buffalo fly populations on steers were reduced by 52, 64 and 77% respectively and resulted in corresponding increases in average liveweight gain of 15% (0.084 kg/day), 11% (0.087 kg/day), and 4% (0.018 kg/ day) in treated herds. The effect of the treatment on weight gain was statistically significant in the second experiment only, when fly populations were highest. There were no differences between breeds in their response to treatment. The results indicate that regular treatment of steers to control buffalo fly does not necessarily promote significant weight gains in this area.