Date of this Version
In a previous paper (Maddock, 1934), it has been shown that healthy calves may be infected with bovine tubercle bacilli when grazed upon pasture infected at intervals with emulsions of the virulent organisms. These infections were designedly heavy, and it was felt that this orientating experiment should be followed by one in which pasture infection was secured in a way more closely approximating to the natural.
Three calves surviving from the previous experiment had reacted strongly to the double intradermal tuberculin test. Microscopic examination of the dung of these animals failed to show the presence of acid-fast bacilli, but to ensure that any natural infection of the dung should be suitably reinforced the three calves were fed on a daily ration of whey heavily infected with emulsions proved to contain virulent tubercle bacilli. When numerous acid-fast organisms appeared in the dung the calves were allowed to graze on the experimental plots for 3 weeks, during which the feeding of infected milk was continue.