| Sumario: | Prospective longitudinal study of major diseases of dairy cattle in Addis Ababa milk shed was conducted for a period of two years. A total of 33 dairy herds with an average of 906 animals were sampled and represented the intra-urban (IU), intra-urban in secondary towns(IUST) and the peri urban (PL9 production sub-systems. Farms were visited weekly and clinical examination was performed on the health status of individual animals. Diagnosis of diseases and causes of death was based on clinical observation. Disease conditions were categorized into eight groups. The annual prevalence rates for all disease conditions were 43.6% and 44.7% for the first and second years, respectively. Both clinical mastitis and reproductive diseases had above 10% whereas astrointestinal disorders, respiratory tract diseases, locomotor disorders and metabolic diseases each had below 5% annual average prevalence rates. The groups of diseases under specific infectious and miscellaneous diseases categories each had an average annual prevalence rate of about 6% . Biological factors considered in terms of age and sex combination influenced diseases occurrence and the youngstock of age less than 12 months had higher prevalence of gastrointestinal and respiratory tract diseases (about 12 % each). The overall disease occurrence was 46.8%, 48.5%, and 33.6% for IQ, IUST and PU sub-systems, respectively. There was an apparently high disease occurrence in the urban settings. The effect of herd size on disease frequencies should that occurrence was relatively lower in farms with larger sizes herd (33%). Reproductive diseases (17.50%) and respiratory tract diseases (9.4%) occurred more frequently in small size herds. Clinical mastitis (10.9%), reproductive diseases (10.5%) and gastrointestinal disorders (9.6%) were more prevalent in herds with medium size. Similarly, the overall prevalence rate of diseases was highest during dry season of the year (20.8%) than during the short rainy (13.1 %) and long rainy (10.7%) seasons. The overall annual mortality rate was 42 per 1000 animals. Gastrointestinal diseases, specific infectious diseases and reproductive tract diseases ranked as the first three top important diseases which caused mortality. In conclusion, prior to launching interventions against the prevailing health problems in the dairy production systems under investigation, further studies on the economic impacts of the major diseases including the subclinical cases is suggested.
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