Characterization of subclinical mastitis in dairy goats herds raised on an organic system in Rio Grande do Sul

Milk and derivates are recognized as vehicle of different pathogens for humans. These micoorganisms may manifest as post-milking contamination or as in infections in the animal itself, particularly in mastitis. The aim of present study was characterizes the occurrence of mastitis and management aspects in dairy-goats raised in three farms of organic milk. The correlation between mastitis and goat husbandry was also investigated. The clinical exam of the mammary glands of 64 dairy-goats did not reveal the presence of clinical mastitis. Nevertheless, the California Mastitis Test (CMT) identified 54 (22.7%) reactive mammary halves (+ or ++). From 238 milk samples collected, 37 (15.6%) were positive for bacterial isolates. Coincident positive results for bacterial isolate tests and CMT were observed in only eight samples, which indicate a sensitivity index of 21.6% for the caprine subclinical mastitis diagnosis test. Coagulase-negative staphylococci (CNS) were identified as the most frequent pathogen in milk samples (83.8%). The in vitro sensitivity test revealed CNS strains resistant to cotrimoxazole (50%), ampicillin (48.1%), nitrofurantoine (7.7%), cefaclor (7.14%), and oxacilline (3.85%). Cefalotine, gentamicin, neomycin, streptomycin, and tetracycline were the most effective drugs. No correlation was observed between the occurrence of subclinical mastitis and race, lactation period, drinking water quality in farms, or milking system as adopted in the present study.

Mastitis; goat; organic milk; coagulase-negative staphylococci; antimicrobial resistance