Prevalence of bovine mastitis, risk factors, changes in milk composition and bacterial isolation in and around Modjo town, central Ethiopia

A cross-sectional study was conducted on 316 lactating dairy cows from November 2021 to May 2022 in and around Modjo. The main objectives of this study include estimating the prevalence and isolation of aerobic bacterial pathogens and observing compositional changes in mastitic milk. To this end, mastitis was diagnosed both clinically and using California mastitis test (CMT). Isolation of major aerobic pathogens and alterations in milk composition were determined using their respective standard techniques. Accordingly, the overall prevalence of mastitis observed in the study was 72.8%, of which 9.5% was clinical and the rest 63.3% subclinical mastitis. Quarter level prevalence was 45.2%. Among the potential risk factors considered, the presence of teat/udder injury, poor udder and farm hygiene showed higher prevalence of mastitis (p < 0.05) compared to the corresponding categories. The most predominant bacterial pathogen isolated was Staphylococcus aureus (11.25%), followed by E. coli (10%), Micrococcus species (10%) and Pseudomonas aeruginosa (10%). Protein, solid non-fat (SNF), pH and freezing point measurements showed statistically significant difference (p < 0.05) between milk from mastitic and non-mastitic udders. However, fat and density were not statistically different (p > 0.05). In conclusion, mastitis was highly prevalent and clinically important disease of dairy cows in the study area and hence deserves attention to minimize its impact. Cows’ udder and farm should be kept clean as much as possible to reduce the prevalence of mastitis. Some of these bacterial isolates can be the real causes of mastitis. However, studies should be conducted to establish causal relationship.