Fly Sprays for Dairy Cows–A Progress Report

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Abstract
Fly sprays of petroleum oils carrying pyrethrum, pine oil, or both, designed to keep flies from dairy cows were tested for their efficiency. It was shown that all had approximately the same efficiency for the first hour but differed at subsequent intervals, pine oil increasing their efficiency in proportion to the amount applied. Burning followed the use of oils having a viscosity lower than 40 seconds irrespective of the unsulfonated residue while oils with unsulfonated residues below 90 per cent were dangerous if used in oils of higher than 65 seconds viscosity. The pyrexial point, defined as the environmental temperature above which cows could not maintain a normal body temperature, was determined for the experimental animals. The application of oil sprays lowered this pyrexial point approximately five degrees by impairing the small amount of cooling that takes place, through the action at the surface of the skin. The different sprays varied in their effects on this pyrexial point.

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