The overall prevalence of mastitis in the current study at cow level was found to be 25.16%. This is comparable with the result of (17), who recorded an overall prevalence of 28.2% at Bahir Dar and its surroundings. But it is a bit lower than the report of (18) 34.9% in the southern Ethiopia. The present study was very low when compared with the work of (19, 20), who reported a prevalence of 64.4% in Asella and 52.78% in and around Sebeta, respectively. The variation could be attributed to management differences, breed considered and agro-climatic condition.
The overall prevalence of mastitis at quarter level was found to be 10.43%. This quarter level mastitis prevalence was in agreement with (21) who reported 10% dairy farms of Holleta town and (22) reported 13.6% in small-scale dairy farms of Adama town. However, it was higher than the result of (23) who reported 2.4% in small-scale dairy farms of Selalle and lower than the report (24) 29.0% in Adama dairy farms. Differences in husbandry practices like management practices and other interventions between different areas might be the reason to difference in prevalence reported by various researchers.
The prevalence of clinical and sub clinical mastitis recorded at cow level in the present study was 3.64% and 21.52%, respectively. This finding is comparable with the report of (17), who reported clinical prevalence of 3% and subclinical cases of 25.2% at Bahir Dar and its surroundings. However, it is a bit lower than the findings of (25), who recorded 5% clinical and 32. 2% sub clinical cases in the urban and peri-urban dairy farms at Addis Ababa, central Ethiopia. The results of both clinical and subclinical mastitis in this study are much lower than that of previous reports (12, 18, 19, 20, and 26). This could be attributed to better attention and well informed of dairy holders about the effect and consequence of mastitis form time to time.
In the current study, the dominant and most prevalent bacteria identified during bacteriological examination were Staphylococci species followed by Escherichia coli. This finding is in line with the report of various researchers (12, 20, 21, 22, and 23). The dominance of this pathogen may be ascribed to the lack of proper milking procedure for instance absence of pre and post teat dipping using antiseptics, washing of milker’s hands and using teats secretion as a lubricant of teats at the time of milking which is often practiced in the study area might have contributed to the spread of these pathogens from the milker’s and infected teats to healthy ones.
In the present study, the environmental bacteria Escherichia coli were isolated in high proportion 16.94%.This is in agreement with the reports of (20, 22) who found this isolate in high proportion. The presence of environmental bacteria might be an implication of unhygienic milking practice and contamination of cows’ teats and environment with their dung in the study area.
The prevalence of mastitis was higher in poor conditioned cows then good once. This finding is in agreement with reports made by different authors in different parts of the country (22 and 27) who found body condition as one of associated risk factors to mastitis. Animal with poor body condition might experience their immune system not functioning well, thus making them more susceptible to mastitis.
Prevalence of mastitis was significantly associated with milking hygienic practice. Cows
with poor milking hygiene standard are severely affected than those with good milking hygiene condition. This finding is supported by (20, 28, 29) who evidenced the association of hygienic condition to the occurrence of mastitis. This might be due to absence of udder washing, milking of cows with common milkers’ and using of common udder cloths, which could be vectors of spread especially for contagious mastitis.
Multiparous cows showed higher prevalence than primiparous cows. This is in agreement with (12, 17, 18, 20, 27, 30) and) who identified parity as risk factor to mastitis in the study conducted at different parts of Ethiopia. As animals produce more and more calves there is risk of contracting bacteria responsible for mastitis and as age goes one the level of immunity reduces
Lactation stage was found to be a risk factor to mastitis and the prevalence was highest in early lactation than mid and late stage of lactation. The result of the current study is in line with (18) who reported mastitis prevalence was higher in early lactation. But it disagrees with the finding of (12, 23) who reported prevalence of mastitis was higher in late stage of lactation. The variation could be attributed to different management practiced in different study areas. The highest prevalence during the early lactation is an indication of infection, probably prior to freshening. It may also be reflection of important changes that occur prior to parturition period in endocrine, nutritional and metabolic status which compromise the immunity of the cow (31).
More cows which had experienced mastitis problem before were found to be more positive to mastitis at current investigation than non-exposed ones. This is comparable with the findings of (18, 22) who indicated cows with previous exposure to udder infection were more likely to be re-infected than those never exposed. This might be attributed to possibility of previously exposed cows remained at carrier state and inefficacy of drugs used for mastitis treatment in the study area.
The presence of teat lesion was found to be one of the risk factors to the development of mastitis. Cows with teat lesion showed significantly higher prevalence of mastitis than those without lesion. This is in agreement with report of (20, 30). This might be attributed to more exposure to infection due to more contact with contaminated environment that make the lactating cows to be prone for mastitis.
Prevalence of mastitis was significantly associated with cleaning practice. The rate of mastitis was higher in lactating cows in which the owner’s utilized same clothing to clean all udders than those not doing. This is in line with (32, 33) who reported the same scenario. This might be due to milking of cows with common milkers’ and using of common udder cloths, which could favor the proliferation and transmission of mastitis causing organisms.
Milking of infected cow teat last was associated to lower prevalence of mastitis. The infection rate was significantly lower in lactating cows from dairy farms practicing lactation of affected cow last than those not practicing it. The findings of the present study complys with (17) who support the prevention effect of milking affected cows and teat last.