Bovine Mastitis in Zebu and Crossbred Cattle under the Extensive Management System in Tanzania

A study was carried out to evaluate the incidences and causes of bovine mastitis in Tanzanian shorthorn zebu (Bos indicus) in the traditional sector and crossbred cows (Bos taurus${\times}$Bos indicus) in the dairy ranching sector, both found under the extensive range management system. Management practices were evaluated through a survey study using structured questionnaires. A total of 120 lactating cows (60 cows from each sector) were screened for the disease using the California Mastitis Test (CMT). Confirmatory tests used for infected cows included; the Direct Microscopic Somatic Cell Count (DMSCC), culture, bacteriological and biochemical laboratory assays. Survey results showed that management practices were generally very poor in both sectors with 84% of the surveyed herds being kept and milked under very unhygienic environmental conditions. The level of infection was higher in the crossbred cows (5% clinical and 38.3% sub-clinical mastitis) and lower in the zebu cows with only sub-clinical mastitis (23.3%). Crossbred cows had (p<0.05) higher somatic cell counts than zebu cows. The four highest-ranking bacterial isolates in order of importance were Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Bacillus spp. It was concluded that bovine mastitis under the extensive management system in Tanzania was a result of poor management practices and that zebu cows were more resistant to the diseases than crossbred cows.