The Value of Hypochlorite and Quaternary Ammonium Compounds, when Used in Udder Washes, in Reducing the Plate Count of Milk

Various bactericidal agents now are in general use in solutions for washing the udders of cows prior to milking. Comparatively little information is recorded regarding their value in reducing the plate count of the milk produced. Scales and Kemp (6) reported that 2 minutes was too short a period for chlorine to yield dependable sterility. Other workers, Bryan et al. (2) and Waugh et ~. (9), have shown that no viable organisms were present in recommended concentrations of chlorine. Spurgeon et al. (8) compared the bactericidal activity of hypochlorites and quaternary ammonium compounds. When applied to teats which had been inoculated with a suspension of Streptococcus galavtiae, these germicidal solutions did not eliminate all the organisms present but did destroy 90 per cent of those that would have remained after ordinary rinsing of teats with non-germicidal solutions. Mueller et al. (5) found that approximately 0.3 per cent of cow feces or nonfat milk solids produced a significant decrease in germicidal potency of a 200 p.p.m, quaternary ammonium solution. Keith and Reaves (4) washed udders with quaternary ammonium compounds, chlorine, and plain water. They believe the quaternary ammonium compounds are effective sanitizing agents. Byers and Ewalt (3) reported a reduction of 34.2 per cent in the plate count of milk produced when the udders of cows were washed with chlorine solutions.