Longitudinal study of the effects of teat condition on the risk of new intramammary infections in dairy cows.

Machine milking-induced alterations of teat tissue may impair local defense mechanisms and increase the risk of new intramammary infections. The objective of the current study was to assess the influence of short-term and long-term alterations of teat tissue and infectious status of the udder quarter on the risk of naturally occurring new intramammary infections, inflammatory responses, and mastitis. Short-term and long-term changes in teat condition of right udder quarters of 135 cows of a commercial dairy farm in Saxony-Anhalt, Germany, were recorded monthly for 10 mo using simple classification schemes. Quarter milk samples were collected from all examined quarters at each farm visit. Bacteriological culture results and somatic cell counts of quarter milk samples were used to determine new inflammatory responses (increase from ≤100,000 cells/mL to >100,000 cells/mL between 2 samples), new infections (detection of a pathogen from a quarter that was free of the same pathogen at the preceding sampling), and new mastitis (combination of new inflammatory response and new infection). Separate Poisson mixed models for new inflammatory responses, new infections, and new mastitis caused by specific pathogens or groups of pathogens (contagious, environmental, major, minor, or any) were used to estimate risk ratios and 95% confidence intervals. Data preparation and parameter estimation were performed using the open source statistical analysis software R. We observed no effect of any variable describing teat condition on the risk of new intramammary infections, inflammatory responses, or mastitis. Intramammary infections of the same udder quarter in the preceding month did not affect risk either.

[Evaluation of bacteriological diagnosis in secretions of clinical mastitis cases with Petrifilm™ in the veterinary practice laboratory]. / Evaluierung der bakteriologischen Diagnostik von Sekreten klinischer Mastitiden mit Petrifilm™ im tierärztlichen Praxislabor.

OBJECTIVE: Especially in cases of clinical mastitis a rapid test for identification of responsible pathogens would be useful for choosing the appropriate treatment. The objective of the study was to determine whether two rapid tests are suitable to detect infections with coliforms and Staphylococcus aureus, respectively, in cows with acute mastitis under field conditions. MATERIAL AND METHODS: The evaluated tests were "Petrifilm™ Rapid Coliform" and "Petrifilm™ Staph Express Count System". A total of n=107 double, quarter foremilk samples from dairy cows with clinical signs of acute mastitis was obtained aseptically. All samples were examined microbiologically by means of both conventional methods and using both Petrifilm™ tests. RESULTS: Overall sensitivity for the Petrifilm™ tests was 32%, overall specificity 90%, and the positive predictive value 24%. In contrast, conventional methods yielded positive results in only 18% of cases, meaning that with the petrifilm kits, 3.5 times more infections caused by coliforms could be detected. However, not all coliforms cultivated conventionally were also identified by the Petrifilm™ tests. CONCLUSION AND CLINICAL RELEVANCE: These unsatisfactory results may be due to flaws in the conventional culturing or contamination of samples. Therefore, the results of this field trial do not lead to a conclusive evaluation of this diagnostic device under field conditions, although the Petrifilm™ test for coliforms may already be recommended to identify infections caused by gram-negative microorganisms. Once caution is taken at sampling, this kit may lead to a basic decision regarding therapy.