Studies on the hygiene of drinking water for laboratory animals. 1. The effect of various treatments on bacterial contamination.

Daily autoclaving of drinking-water bottles or daily replacement of their contents resulted in drinking water hygienically acceptable for laboratory rats. However, daily autoclaving of the bottles imposes an additional workload which many institutions cannot afford. The daily replacement of the drinking water is not desirable, since with the usual routines it is virtually impossible to guarantee a bottle is returned to the same cage. A reliable method of preventing bacterial growth for more then 1-2 days in the drinking water of conventional laboratory rats is its acidification with hydrochloric acid to pH 2.3-2.5.