USE OF CLINICAL-PARAMETERS FOR DIFFERENTIATION OF GRAM-POSITIVE AND GRAM-NEGATIVE MASTITIS IN DAIRY-COWS VACCINATED AGAINST LIPOPOLYSACCHARIDE CORE ANTIGENS
De. Morin et al., USE OF CLINICAL-PARAMETERS FOR DIFFERENTIATION OF GRAM-POSITIVE AND GRAM-NEGATIVE MASTITIS IN DAIRY-COWS VACCINATED AGAINST LIPOPOLYSACCHARIDE CORE ANTIGENS, Journal of the American Veterinary Medical Association, 212(9), 1998, pp. 1423
Objective-To determine whether clinical parameters could be used to di
fferentiate clinical mastitis (CM) caused by gram-positive bacteria fr
om CM caused by gram-negative bacteria in dairy cows vaccinated agains
t lipopolysaccharide core antigens. Design-Case series. Animals-143 ep
isodes of CM in 86 dairy cows in a single herd. Procedure-Cows were ex
amined at onset of CM, and 24 clinical parameters including rectal tem
perature, heart rate, rumen contraction rate, degree of dehydration, v
arious udder and milk characteristics, lactation number, stage of lact
ation, and season of year were recorded, Milk production and milk cons
tituent concentrations before onset of CM were obtained from Dairy Her
d Improvement Association records. Values for cows with gram-negative
CM were compared with values for cows with gram-positive CM. Logistic
regression was used to identify important predictors of gram-negative
CM. Results-64 (45%) CM episodes were caused by gram-negative bacteria
and 79 (55%) were caused by gram-positive bacteria. Rumen contraction
rate was significantly lower and milk protein percentage before onset
of CM was significantly higher in cows with gram-negative, rather tha
n gram-positive, CM. Logistic regression indicated that CM was more li
kely to have been caused by gram-negative bacteria if it developed dur
ing the summer, milk was watery, or rumen contraction rate was low. Se
nsitivity and specificity of the final regression model were 0.58 and
0.80, respectively. Predictive value of a positive result was 0.74 whe
n proportion of CM episodes caused by gram-negative bacteria was assum
ed to be 50%. Clinical implications-Results suggest that clinical obse
rvations do not allow accurate prediction of CM pathogens and should n
ot be the sole criteria for deciding whether cows with CM are treated
with antibiotics.