Associations between Mycobacterium paratuberculosis sero-status, milk quality parameters, and reproduction in dairy...

The objective of this study was to investigate the influence of Mycobocterium avium subsp. paratuberculosis (MAP) sero-status of dairy cows on different milk production variables and reproductive traits. The study was carried out on 40 herds from the region of Galicia (North-West Spain). These herds were randomly selected from a larger group that had taken part in a voluntary paratuberculosis control program since 2005, which involves regular serum sampling of every adult animal to run antibody-ELISA tests. Milk production and reproductive data were obtained from the "Dairy Herd Improvement Program (DHIP) of Galicia". All the gathered data were processed following a linear regression model. Results indicated that there was no significant effect of MAP sero-status on individual milk production variables. However, a significant difference was observed at the calving-to-first-insemination interval, with an average increase of 14 days in positive animals compared to negatives. It has to be taken into consideration that the paratuberculosis status was only defined by the serological status. Since para tb-infected animals may have antbodies or may not, para tb-positive animals can also be included in the sero-negative group of animals, which may bias the results.