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Objective

To determine whether antibiotic and supportive treatment would improve outcome for dairy cows with naturally developing clinical mastitis, compared with supportive treatment alone.

Design

Randomized controlled trial.

Animals

124 cows in one herd with 172 episodes of clinical mastitis.

Procedure

Cows were examined at the onset of clinical mastitis, assigned a severity score, and randomly assigned to receive antibiotic (intramammary administration of cephapirin, IV administration of oxytetracycline, or both) and supportive treatment (administration of oxytocin, stripping of affected glands, and, in severely affected cows, administration of flunixin meglumine or fluids) or supportive treatment alone. Treatment was continued until 24 hours after signs of clinical mastitis resolved (clinical cure). Milk samples from affected glands were submitted for bacterial culture before initial treatment and every 2 weeks thereafter until the causative organism was no longer isolated (bacteriologic cure).

Results

When mastitis was caused by Streptococcus spp or coliform bacteria, clinical cure rate by the tenth milking was significantly higher if antibiotics were used. Bacteriologic cure rate at 14 days was significantly higher when antibiotics were used, particularly if mastitis was caused by Streptococcus spp. Cows receiving antibiotics developed fewer subsequent episodes of clinical mastitis during the 60 days after the initial episode of mastitis and had less severe clinical disease than cows that did not.

Clinical Implications

Results suggest that, in herds in which mastitis is often caused by environmental bacteria, antibiotic and supportive treatment may result in a better outcome for cows with clinical mastitis than supportive treatment alone. (J Am Vet Med Assoc 1998;213:676-684)

Free access
in Journal of the American Veterinary Medical Association

Objective

To determine whether clinical parameters could be used to differentiate clinical mastitis (CM) caused by gram-positive bacteria from CM caused by gram-negative bacteria in dairy cows vaccinated against lipopolysaccharide core antigens.

Design

Case series.

Animals

143 episodes of CM in 86 dairy cows in a single herd.

Procedure

Cows were examined at onset of CM, and 24 clinical parameters including rectal temperature, heart rate, rumen contraction rate, degree of dehydration, various udder and milk characteristics, lactation number, stage of lactation, and season of year were recorded. Milk production and milk constituent concentrations before onset of CM were obtained from Dairy Herd 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 than gram-positive, CM. Logistic regression indicated that CM was more likely to have been caused by gram-negative bacteria if it developed during the summer, milk was watery, or rumen contraction rate was low. Sensitivity and specificity of the final regression model were 0.58 and 0.80, respectively. Predictive value of a positive result was 0.74 when proportion of CM episodes caused by gram-negative bacteria was assumed to be 50%.

Clinical Implications

Results suggest that clinical observations do not allow accurate prediction of CM pathogens and should not be the sole criteria for deciding whether cows with CM are treated with antibiotics. (J Am Vet Med Assoc 1998;212:1423–1431)

Free access
in Journal of the American Veterinary Medical Association

Objective

To determine whether mammary gland or colostral characteristics at calving could be used to predict colostral immunoglobulin G1 (IgG1) concentration or intramammary infection (IMI) and whether leakage of colostrum affects IgG1 concentration.

Design

Prospective study.

Animals

113 multiparous Holstein cows.

Procedure

Cows were examined within 3 hours of calving, and mammary gland and colostral characteristics, colostral volume, somatic cell count, and concentrations of IgG1, fat, and protein were determined. Bacteriologic culture of mammary secretions was performed approximately 14 and 7 days before calving and at calving. Associations of gland and colostral characteristics with colostral IgG1 concentration, colostral volume, and IMI were examined.

Results

Thick or thin colostrum had higher IgG1 concentration than colostrum of intermediate viscosity. Colostrum from mammary glands that were firm had low IgG1 concentration. Colostral IgG1 concentration was weakly correlated with volume. Intramammary infection was likely to be detected if colostrum contained clots or blood or if the California Mastitis Test (CMT) score was ≥ 2. Somatic cell count was higher for glands with IMI than for uninfected glands, and CMT score was correlated with cell count.

Clinical Implications

Mammary gland and colostral characteristics were of little value in predicting IgG1 concentration. Our findings do not support recommendations that first milking colostrum that is thin (watery) or that is from cows producing large volumes not be fed to dairy calves. Colostral characteristics, particularly CMT score, were of value for predicting IMI. (J Am Vet Med Assoc 1999;214:1817-1823)

Free access
in Journal of the American Veterinary Medical Association