Assessment of the evolution of the proportion of respiratory and enteric pathogens and diseases in pre-weaned unvaccinated dairy heifers from Québec, Canada

The objective of this study was to describe the proportion of enteric and respiratory pathogens and diseases in unvaccinated pre-weaned dairy heifers, in their first 2 weeks of life (exam 1), and at 4- to 8-weeks old (exam 2). Heifers from 20 dairy herds were examined and sampled twice for respiratory and enteric pathogens and diseases. Respiratory health score and ultrasonographic lung consolidation were assessed, and nasopharyngeal swabs, blood samples, and feces samples were collected. The prevalence for each disease and pathogen was described, and the difference between exams 1 and 2 was assessed. A total of 198 heifers were included at exam 1, and 182 of them were examined again at exam 2. At exam 1, the prevalence of respiratory diseases (positive clinical score or presence of lung consolidation) and diarrhea was 18% and 23%, respectively. At exam 2, the prevalence of respiratory diseases and diarrhea was 62% and 13%, respectively. Heifers were less likely to have respiratory diseases and pathogens at exam 1 than exam 2, and were more likely to have diarrhea at exam 1 than exam 2. These results help in understanding the dynamic of respiratory and enteric pathogens and diseases.