[The effectiveness of the repellents diethyltoluamide and phenylpropandiol in grazing primiparous cows].

In practical farming conditions of an agricultural enterprise situated in South-East Moravia, the repellents N,N'-diethyl-m-toluamide and 2-phenyl propanediol 1,3 were tested after their application to grazing first-calves of the Bohemian Pied breed. The experiment was conducted in July and August 1986 and it took 40 days. In the first experimental group, 2-phenyl propanediol 1,3 was applied and in the other group a 1:1 mixture of the repellents N,N'-diethyl-m-toluamide and 2-phenyl propanediol 1,3 in form of a 10% water emulsion in the interval of 48 hours. No flights and bites of annoying insects (gad-flies, black-flies, gnats, midges, symbovine flies) were observed in treated first-calves in the two experimental groups. The economic efficiency of 2-phenyl propanediol 1,3 application in the first experimental group was manifested by the higher milk yield by 1.20% and by the higher milk fat yield by 0.13%; when the mixture of N,N'-diethyl-m-toluamide and 2-phenyl propanediol 1,3 was used, the milk yield increased by 2.27% and the milk fat yield by 0.17%, in comparison with the control group. Considering that some meteorological factors had worse values in the test year, after their mathematico-statistical evaluation they had significantly different values from those recorded in the two preceding years, the differences in milk production and fat percentage were not statistically significant.