|Bradner, Laura -|
|Beitz, Donald -|
|Robbe-Austerman, Suelee -|
Submitted to: Iowa State University Animal Industry Report
Publication Type: Review Article
Publication Acceptance Date: January 20, 2013
Publication Date: February 4, 2013
Citation: Bradner, L., Stabel, J.R., Beitz, D.C., Robbe-Austerman, S. 2013. Shedding of Mycobacterium avium subsp. paratuberculosis into milk and colostrum of naturally infected dairy cows over complete lactation cycles. Iowa State University Animal Industry Report. A.S. Leaflet No. R2793. Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd. Shedding of this bacterium into the milk of infected dams is one mode of transmission to young calves. However, there is very little data to determine how much shedding occurs. The present study evaluates the shedding of the bacteria into colostrum and milk durinig the 305-day lactation cycle. These results are critical for producers to understand and to assess exposure of calves to the bacteria on-farm.
Technical Abstract: The primary mode of transmission of Mycobacterium avium subsp. paratuberculosis (MAP) is fecal-oral. However, MAP is also shed into the milk and colostrum of infected cows. The objective of this study was to identify if an association exists between stage of MAP infection and days in lactation with the amount of MAP present in milk and colostrum of naturally infected cows. Results indicated that MAP is primarily shed in early lactation and in cows with advanced infection. This provides crucial information to dairy producers pertaining to the threat of MAP transmission via milk and colostrum. Producers now know that allow a calf to suckle even once is exposing it to the highest concentrations of MAP and therefore possibly infecting the newest generation of animals.