The present study assessed the antibiotic susceptibility patterns of Escherichia coli and Salmonella isolates of raw milk from zero grazed cows. A total of 65 milk samples were collected for analysis. The standard membrane filtration technique and HiCrome E. coli agar were used in isolation of E. coli from milk samples. Isolation of Salmonella species employed pre-enrichment in buffered peptone water followed by enrichment in Rappaport and Vassilidis broth prior to Xylose lysine deoxychocolate agar as a differential media. The isolates were analyzed for antimicrobial susceptibility to eight different types of antibiotics using disc diffusion method. The prevalence of E. coli was 16 (16.7%) and all the samples tested were negative for Salmonella. The average colony forming unit for E. coli was 2cfu/mL. All E. coli isolates tested were resistant to penicillin (100%) and amoxicillin-clavulanic acid (100%) while 15(93.8%) were sensitive to ciprofloxacin. Resistance was also observed in sulfamethoxazole-trimethoprim (43.8%), chloramphenicol (12.5%), oxytetracycline (68.8%), streptomycin (12.5%) and gentamicin (25%). Of the isolates tested, 14 (87.5%) showed multi-drug resistance pattern. These results confirm that milk from zero grazed cows in Arusha was contaminated with E. coli, and that most of the E. coli strains isolated were resistant to at least one of the antimicrobial agent commonly used in treatment of human diseases.

This study aimed at investigating the animal health management practices in zero grazing dairy units. A questionnaire was used to assess the veterinary practices including the administration of antibiotics and other veterinary inputs to promote growth, prevent and treat diseases. Sixty-five (65) respondents were involved in the study. All the respondents (100%) reported that they did not use growth promoters while 98.5% reported the use of prophylactic vaccines. No withdrawal periods were observed for all the prophylactic vaccines given to animals as instructed by Ward Livestock Officers that the vaccines were not harmful to the health of consumers. Of the 65 respondents, 95.4% (62) reported the use of therapeutic antibiotics. The withdrawal period for therapeutic antibiotics ranged from 1 to 3 days as reported by 60% of the respondents while 24.6% (16) reported the withdrawal period of between 4 to 7 days, 4.6% did not observe withdrawal periods and 6.2% depended on the instructions from the veterinarians. Of the respondents, 53.8% attended animal health management training and 59.6% kept no records for any health interventions made to their animals. Based on the observational findings, majority (84.6%) of the cow's enclosures were of poor hygiene. Warm water was used by 87.7% of the respondents to wash the udders prior to milking, 93.8% used towels to drain water from the udder(s) and100% of farmers lubricated the teats with udder salve prior to milking. Poor hygiene of the enclosures and washing the udders instead of teats only may predispose animals to infectious disease and this may lead to increased use of antibiotics, which may result into emergence of antibiotic resistance. It is, therefore, recommended that farmers should be trained on best animal health management practices such as teat washing, removal of manure from the animal pens as preventive measures for infectious diseases as well as improving the health and productivity of their animals.