Johne's disease in cattle continues to receive a great deal of media attention. Much of the concern focuses on controlling or eliminating the disease in cattle because the bacterium (Mycobacterium paratuberculosis) may be partially associated with disease in humans.

oes pasteurization kill the bacterium? This is an important question for humans. It is also important in animals if we want to pasteurize waste milk for calves. Recent reports in the news media reveal that cultures from many samples of milk from grocery stores did reveal a very limited number of positive isolates of mycobacterium paratuberculosis. These reports have forced public health officials to take a closer look at pasteurization.

Dr. J. Stabel performed a recent study to determine if on farm pasteurization of waste milk would destroy mycobacterium paratuberculosis. His results were published in 200l J. Dairy Sci. 84: 524-527.

Dr. Stabel studied a dairy herd that had 20% of the cows test positive for Johne's disease. The dairy had a batch pasteurizer that was used for heat treatment of waste milk. The milk was heated for 30 minutes at 65.5 degrees C. before feeding to calves.

Waste milk was inoculated with M. paratuberculosis at varying concentrations from 1,000 to 5,000 colony farming units (cfu) per milliliter of milk. The milk was then heated to 65.5 degrees C. When the waste milk got to 65.5 degree C. samples were collected at 0, 15, and 30 minutes. The results revealed that no bacteria was present in the samples at 0, 15, or 30 minutes.

These results indicate that pasteurization of waste milk at 65.5 degree for 30 minutes proved to be adequate to destroy all of the M. paratuberculosis in the waste milk.

In the U. S. there are currently at least three companies that market pasteurizors for dairies. Some dairymen use hot water in plate coolers or bulk tanks to heat milk. Care must be used to insure that bacteria are actually killed and the pasteurizor can be thoroughly cleaned. If bacteria are not killed, then heated milk actually becomes an incubator.

Research projects are now in progress that evaluate feeding raw waste milk verses pasteurized waste milk to calves. They are designed to evaluate the long term effects on calves and to monitor the incidence of Johne's disease. They also will evaluate the economics of calf milk pasteurization.

Pasteurization of colostrum is being studied. Colostrum sometimes forms a thick gel when pasteurized. Researchers are trying to determine methods to effectively pasteurize colostrum and not destroy any of its antibody activity.

Hill Top Dairy is considering pasteurizing waste milk for calves. We may purchase a unit that heats milk to 162 degrees F. The unit will pasteurize 20 or 40 gallons per hour. This unit was recently introduced to the market. I am trying to find independent research that it will kill mycobacterium paratuberculosis and other organisms in waste milk.