STUDY OF SUBCLINICAL MASTITIS IN A HERD OF GIR AND CROSSBRED COWS II. PREVALENCE, ETIOLOGY AND SENSITIVITY

ABSTRACT

The objective of this study was to investigate the occurrence of subclinical mastitis (sem) in a herd of Gir and crossbred cows. Milk samples were collected on a farm located in Ribeirão Preto, SP, Brazil, on 7 occasions in the period of June/1992 to January/1994. A total of 373 samples were collected from sem CMT positive quarters. The herd sem índex was high (47. 63%), , and there was no statistical difference between the Gir sem índex and the crossbred one. The most prevaleht bacteria was Staphylococcus spp, followed by Escherichia coli and other Enterobacteriaceae, Streptocdccus spp, and Corynebacterium spp, with the frequencies of 87.0%, 25.6%, 17.9% and 4.0%, respectively, found in the samples which had bacterial growth (86.9%), in pure culture or in association with other bacterias. Pasteurella spp was found in the frequency of 1.8%, only in association with. other bacterias. The study of bacterial sensitivity to antibiotics by the antibiogram revealed that cephalosporine was the best drug against the most prevalent bacteria (Staphylococcus spp, E. coli, and Streptococcus spp) with 99.7% of sensitive samples, followed by chloramphenicol with 96.6%, gentamycin with 93.4%, kanamycin with 93.0%, fluorquinolone 89.5%, ampicillin with 86.5%, neomycin with 83.6%, and espiramicin with 76.4%.

KEY WOROS:
Subclinical mastitis; frequency; sensitivity; cattle; Gir; crossbred