Short communication: Diagnostic accuracy of the Petrifilm culture system for identifying colostrum with excessive bacterial contamination in Quebec dairy herds

The objective of this study was to validate the diagnostic accuracy Petrifilm culture system (3M, St. Paul, MN) for identifying colostrum with excessive bacterial contamination. An observational cross-sectional conducted between October 2015 and February 2016. Two aliquots were collected during first meal 332 calves (33 commercial Holstein dairy farms) in Quebec, Canada. One aliquot per calf used quantify total bacteria count coliform using standard bacteriological laboratory testing (reference test). These results dichotomized identify contamination [aerobic plate (AC) >100,000 cfu/mL; (CC) >10,000 cfu/mL]. both aerobic other from each calf. As such, AC CC according manufacturer's recommendations. area under curve receiver operating characteristic compared 0.83, 0.95, respectively. Using optimal threshold >24,000 cfu/mL results, had a sensitivity (Se) 69%, specificity (Sp) 86%, kappa value 0.54. >4,000 Se 93%, Sp 90%, 0.64. Overall, these suggest that is an appropriate alternative