1a.Objectives (from AD-416)
The objective of this study is to evaluate the effectiveness of feeding heat-treated colostrum to calves in herds infected with Mycobacterium avium subsp. paratuberculosis (MAP). Since MAP is shed into the milk of infected dams, feeding colostrum from naturally infected dams can be a potential source for transmission of infection to neonatal calves. Pasteurization has proven effective in the destruction of viable MAP in colostrum and waste milk on-farm. However, little is known about the long-term effects of feeding pasteurized colostrum on the general health of the calf. Even less data are available documenting effects of feeding pasteurized colostrum on MAP infection in calves. We will receive colostrum samples from naturally infected dams from each of the selected herds within the study and determine the presence of MAP within the samples in order to evaluate the potential exposure of the neonates to the bacterium.
1b.Approach (from AD-416)
Colostrum samples will be collected on the day of calving from cows on the study. Up to 600 colostrum samples will be frozen and shipped on ice to the NADC for processing. DNA will be extracted from the colostrum samples by a standard protocol used in the laboratory and then RT-PCR will be performed for the identification of a unique target gene for MAP (ISMap02). The RT-PCR method will include the use of a probe and a standard curve generated by a plasmid control that will allow for semi-quantitation of the MAP bacterium in the colostrum. The goal of the study is to identify colostrum samples that are positive for the MAP bacterium and utilize this information to determine if heat-treatment of colostrum will reduce the risk of transmission of MAP infection to neonatal calves.
This collaborative research project encompasses measures to ensure animal health through the control and management of the disease by improving our understanding of the infection process for neonatal calves. This project has the specific objective to evaluate the effectiveness of feeding heat-treated colostrum to calves in herds infected with Mycobacterium avium subspecies paratuberculosis (MAP) on the general health of the calf and on the incidence of paratuberculosis in the herd. Deoxyribonucleic acid (DNA) extraction and real time polymerase chain reaction (RT-PCR) analyses for colostrum samples were completed. Further studies were conducted to evaluate the presence of MAP on teat skin surfaces concurrent with milk samples from infected cows. In addition, a new PCR method was optimized for use in detection of MAP DNA in milk and colostrum samples. This information provides a useful management tool for dairy producers in allaying the spread of infectious disease to their calves and improving their health. Monitoring of progress and activities were via quarterly conference calls, weekly to monthly email exchanges, and occasional face to face visits at national meetings.
Evidence suggests that calves can become infected shortly after birth by exposure to pathogens such as MAP, in either the feces, colostrum, or milk of infected dams. Pasteurization of colostrum is an economical alternative to commercial colostrum products, however, little is known about its effectiveness in destroying pathogens or on the immunoglobulin content. The objective of this study is to evaluate the effectiveness of feeding heat-treated colostrum to calves in herds infected with MAP on morbidity and mortality rates. Results demonstrated that colostrum could be heated to 60°C for up to 120 minutes before a significant reduction in IgG occurred. Further studies determined that Mycoplasma, Listeria, E. coli, Salmonella, and MAP in colostrum were inactivated at a time/temperature treatment of 60°C for 30 minutes. These studies contributed to the current regime of 60°C for one hr as the industry standard for on-farm batch pasteurizer units. An additional study was designed to correlate fecal excretion of MAP with the presence of MAP in colostrum and on teat skin surfaces of cows. This work demonstrated that MAP DNA detection in colostrum and teat swab specimens increased with increasing MAP fecal shedding. Although further studies need to be conducted this work provides insight into the need for management of dams and calves on-farm to prevent or reduce the spread of paratuberculosis.