[The effect of blood-sucking diptera on the weight of grazing heifers].

: It was demonstrated experimentally that bloodsucking dipterans (gad-flies, gnats, midges, black flies) influenced negatively weight increments of grazing heifers and that it was suitable to treat the heifers with repellents; 10% water emulsion of the repellent diethyltoluamide was used for heifer spraying in the intervals of 48 hours. Over the 66 days of the experiment, the total live weight of one heifer from the test group increased by 5.00 kg, in comparison with the controls. The coefficient of loss per untreated animal was 105.00 Kcs., the returns of investments per 1.00 Kcs of investment costs were 1.90 Kcs. Owing to worse climatic conditions in the experimental years which significantly differed from meteorological conditions in the previous four years, which ensued from mathematico-statistical evaluation, differences in weight increments over the period of study were statistically insignificant.