Abstract
A study on the prevalence and causes of sub-clinical mastitis was conducted on ten smallholder and large-scale dairy farms in Morogoro urban and peri-urban areas. A total of 65 lactating cows were screened using the California Mastitis Test (CMT). Confirmatory tests used included; the direct microscopic somatic cell count (DMSCC), culture, bacteriological and biochemical tests. Structured questionnaires were used to collect information on management aspects. Results showed 62% and 4% cows as sub- clinical and clinical mastitis cases respectively. Levels of infection were higher on smallholder farms (75%) than on large-scale farms (25%). All tested cows had high cell counts (>500,000) per ml of milk. Incidences of mastitis were significantly (p<0.05) related to milking practices. The dominant bacterial isolates in the same order were Staphylococcus aureus, Streptococcus spp, and Escherichia coli. Other organisms isolated included Pseudomonas spp and Klebsiella spp. It was concluded that the high rates of sub-clinical mastitis in the research area were mainly due to poor management and unhygienic milking practices.