The objectives of this study were (1) to describe the change in Mycobacterium avium ssp. paratuberculosis (MAP) antibody milk ELISA-positive prevalence in Canadian dairy herds that participated in a risk assessment (RA)-based Johne's disease (JD) control program; (2) to describe the distribution of so-called high-risk management practices on Canadian dairy farms; and (3) to assess if compliance with selected recommendations translated into changes in the scores of associated RA questions. In Ontario and western Canada, 226 herds voluntarily participated in a RA-based JD control program for several years. In 2005-2007, a previsit survey, RA, and MAP. -antibody milk ELISA of the entire milking herd were conducted. Therefore, the interpretation of the results of this study is strictly for the MAP-antibody milk ELISA status of cows or herds, because no culture of MAP (of fecal or environmental samples) was conducted due to economic restrictions. In early 2008, a telephone interview was used to determine compliance with recommended management changes after the first RA. In 2008-2009, a second RA and another whole-herd MAP antibody milk ELISA were performed. At both herd tests, about 35% of the farms had at least one MAP-antibody milk ELISA-positive cow, classifying them as a MAP-antibody milk ELISA-positive herd. However, 28.8% of herds had changed their MAP-antibody milk ELISA status between the 2 tests, demonstrating that a single herd test was insufficient to determine the long-term MAP-antibody ELISA status of a herd. The average within-herd MAP-antibody milk ELISA-positive prevalence changed from 5.4 to 4.2% over the study period, but management practices did not change much throughout the 2- to 3-yr period and were similar to those reported in other parts of North America. The overall RA scores decreased at the second RA, in particular for management practices in the calving and preweaned calf area, and when herds were test-positive at the first test. This was not surprising, because many of the recommendations at the first RA focused on these management areas and compliance with some recommended farm-specific management practices in this area might be linked to reduced scores for associated RA questions. In conclusion, the participating farms did, on average, decrease their within-herd MAP-antibody milk ELISA positive-prevalence and RA total scores. Changes in RA scores could be linked to improved management practices, indicating that the RA questions appropriately reflected management practices. Some herds changed their MAP-antibody milk ELISA status between tests, which underlines that a current test of the entire milking herd is necessary to determine the present MAP-antibody milk ELISA status of a dairy herd.
Bibliographical noteFunding Information:
In 2005, a pilot study for a voluntary RA-based JD control program was initiated by the Ontario Ministry of Agriculture, Food and Rural Affairs, and CanWest DHI. The program was funded by Canadian Adaptation Council, a granting agency of the federal and provincial governments. Eighty Ontario dairy herds that had known or suspected JD cases in previous years and were enrolled in milk recording programs with CanWest DHI were recruited into the program by 80 practicing veterinarians. The program consisted of a previsit survey about general farm management practices (e.g., manure handling, biosecurity protocols), an RA conducted on farm by the herd veterinarian, and a MAP-antibody milk ELISA of all milking cows done on one DHI test-day. The RA was adapted from an RA developed in the United States by Rossiter et al. (2002) . Table 1 lists the RA questions, their abbreviations, and the range of possible scores. The higher the score, the greater the attributed risk of spreading MAP through a given management practice. The scores were summarized by section and an overall herd score was calculated.
- Johne's disease
- Risk assessment