Short communication: Effect of freezer storage time and thawing method on the recovery of Mycoplasma bovis from bovine colostrum

摘要

ABSTRACTMycoplasma bovisis an important cause of mastitis in dairy cattle, and pneumonia, arthritis, and otitis in calves. Milk and colostrum are considered important sources of infection for calves.knowledge on the effect of on-farm freezing (−18°C) and thawing methods on the recovery ofM. bovisfrom colostrum samples is missing. In this study, 2 separate experiments were performed. The first experiment consisted of a longitudinal study examining the survival [as measured by log(10) reduction] of 2M. bovisstrains in frozen colostrum over 14 wk. The second experiment examined the effect of different thawing temperatures (45 and 20°C), thawing frequencies (once or twice), and initial colostrum titer (104or 106cfu/mL) onM. bovissurvival. A single freeze-thaw cycle led to an approximate 1 log reduction ofM. bovistiter, independent of the thawing temperature. Freezing for 14 wk did not significantly further reduce the titer of bacteria compared with freezing for 2 wk. A second freeze-thaw cycle further reduced theM. boviscount by approximately 0.5 log compared with a single freeze-thaw cycle. Thawing temperature and initial bacterial concentration did not significantly affectM. bovisreduction. In conclusion, storage of colostrum samples in the freezer at −18°C during epidemiological studies, herd monitoring, or test and cull programs will probably have little influence on qualitative bacteriological test results forM. bovis. The epidemiological or clinical relevance of an approximate 1 log reduction ofM. bovisin colostrum is currently unclear.