Introduction: Mozambique has a high potential for dairy farming and milk production. However, in the global dairy industry, mastitis is the main economic significant disease of cattle.

Objectives: This study aimed to determine the prevalence, risk factors, etiology of subclinical mastitis, and the antimicrobial susceptibility of associated bacteria.

Methodology: This was a cross-sectional study in which milk samples from 147 milking cows were collected across smallholder dairy farms in three districts of Manica province, central Mozambique. A questionnaire was used to collect data regarding animal management, milking hygiene and practices. Subclinical mastitis was assessed using the California Mastitis Test. The associated pathogens were isolated on Mannitol salt agar and blood agar, and identified using gram strain, Pastorex Strep (agglutination test) (BioRad, France) and biochemical tests (Api-staph system) (Biomerieu, France). Antimicrobial susceptibility was performed using the diffusion method on Muller Hilton agar.

Results: The study revealed that 105 (71.4%) milk samples were positive to subclinical mastitis. Factors including herd size, multiparity, milk production and milking order were associated with the odds of subclinical mastitis (p <0.05). Among positive milk samples, 89 (84.8%) exhibited bacterial growth, with 58 confirmed as Streptococcus spp. strains. The identified strains included Staphylococcus aureus (36.6%), coagulase-negative Staphylococcus (19.1%), Streptococcus dygalactiae (21.6%), Streptococcus agalactiae (14.1%), Streptococcus bovis (7.5%) and Streptococcus pyogenes (0.8%).  All strains showed high susceptibility to Ceftiofur (72%) and Cloxacillin (42%), and low susceptibility to Pirlimycin (65%) and Polymyxin (41%).

Conclusion: Subclinical mastitis is a major limitation in milk production and causes economic losses in smallholder dairy farms in the study districts. Therefore, appropriate preventing and controlling measures are necessary to reduce subclinical mastitis and its impact on milk production, farmers welfare and food safety.

Keywords: Dairy cows, mastitis, risk factors, microbial contamination