A research study explained on page 29 in the December 2007 issue requires further explanation. The item, titled “Reduce calf exposure to Johne’s,” points out that calves fed heat-treated colostrum from Johne’s-infected cows had lower incidence of the disease than calves fed raw colostrum from infected cows. The item also points out that some of the calves fed the heat-treated colostrum still contracted Johne’s.
Although this is possible, keep in mind that all calves were born to infected cows, which makes infection during pregnancy a possible route of transmission.
In the study, most of the cows were subclinically infected. Published studies indicate that clinically infected dams shedding a high number of the Johne’s organism are more likely to pass Johne’s on to their offspring than subclinically infected cows, explains Judy Stabel, lead scientist with the Johne’s Disease Research Project at the USDA’s
“The point of the study was that feeding a pasteurized product and following that with milk replacer will substantially lower the risk of transmission of (Johne’s) to the neonate,” Stabel says.