Losses in milking qualities of dairy cattle caused by mosquitoes and horseflies and reduction of such losses due to use of diethyltoluamide repellent.

An experiment was carried out in South Bohemia, in which 10% water emulsion of diethyltoluamide was used as repellent against bloodsucking Diptera to protect pastured dairy cattle. The repellent was applied by means of a spraying frame and was effective for 30-36 hours. Seven mosquito species and 18 horsefly species were observed to be attacking the cattle. The average number being 120-300 mosquitoes and 50 horseflies per hour, the milking qualities in the cattle decreased by 6.2%, the milk fat content by 11.8%. After converting to milk with average fat content of 4%, the difference in milking qualities between treated and untreated animals was 9.7%.