Performing Department
Veterinary Pathobiology
Non Technical Summary
The objectives of this study are to describe the relationship between the results of fecal culture, serum ELISA and colostrum culture for Johne's disease, and to describe the molecular epidemiology of Mycobacterium avium subsp. paratuberculosis in fecal and colostrum cultures. Cows in the late dry-period will be enrolled in the study. Fecal and blood samples will be obtained from 1200 cows prior to calving. Soon after calving a colostrum sample will be obtained from the first or second milking. All samples will be processed with standard techniques and all isolates from fecal and colostrum cultures will subtyped with a novel technique. Appropriate statistical methods will be used to accomplish the study objectives. The results will improve our knowledge about the importance of colostrum in Johne's disease transmission and will help farmers to improve their colostrum feeding decisions and strategies.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The first objective of this study is to describe the association between MAP fecal culture or serum ELISA status in late dry-period cows and MAP shedding in their colostrum. The hypothesis to be tested is that moderate and high fecal shedding cows or cows with ELISA S/P>0.8 will also shed the bacteria in their colostrum, and therefore fecal culture and ELISA test results can be used to predict MAP shedding in colostrum. A second objective is to describe the molecular epidemiology of MAP within individual cows' fecal and colostrum cultures, and to compare the distribution of MAP subtypes between fecal and colostrum cultures. The hypothesis to be tested is that fecal and colostrum culture will share a single MAP within an individual cow, but different MAP subtypes are expected among all cows in the study.
Project Methods
The study will take place in an 2000-cow dairy in north central Indiana. Previous studies on the same farm have show that fecal prevalence is approximately 15%, and more than 10% of the culled cows were culled due to Johne's disease clinical signs during 2003. During the study period 800 cows (2nd lactation and more) and 400 first lactation heifers will be enrolled in the study, regardless of their Johnes disease status, from October 01, 2009 until sample size goal is completed (approximately 24 months). Cows with major health problems (such as severe lameness, fracture etc.) at the moment of enrolment will be excluded from the study. Cow and heifer sampling will be performed approximately every 14 days. During the close-up dry period (approximately 1-3 weeks before calving), an approximate 20 g fecal sample will be obtained rectally from each animal using a clean disposable rectal examination glove. Together with each fecal sample, a 10 ml blood sample will be collected. From each cow enrolled in the study, one colostrum sample will be obtained after calving during the first or second milking using the same milking procedure applied by the farm. Fecal samples will be processed using a bacterial culture method previously described (Wells at el, 2002). All blood samples will be tested for detection of antibodies against MAP using a commercial ELISA kit (HerdChek Mpt, IDEXX, Inc.,Portland, Maine). All colostrum samples will be submitted to Dr. Stabel's laboratory (National Animal Disease Center, Ames, IA) for bacterial culture (Stabel, 2002). Molecular subtyping of MAP will be performed on all positive fecal and colostrum culture isolates, using multilocus Short Sequence Repeat Sequencing (SSR) approach (Amonsin et al, 2004). Apparent and true fecal culture, ELISA, and colostrum prevalence will be calculated using standard methods (Martin, 1987). To assess an association between fecal culture results, ELISA, and colostrum culture and PCR, Chi-square test will be used (SAS Inc, 2001). Logistic regression analysis will be used to predict the presence or absence of MAP in colostrum (outcome) using fecal culture and ELISA test results, and parity as independent variables.