Meta-analysis of the prevalence of mastitis and associated risk factors in dairy cattle in Ethiopia

Mastitis is among the most prevalent disease that contributes for the reduction of milk production in dairy herds. Although several published studies have estimated the prevalence of mastitis, variation among studies is great. The objective of the present meta-analysis was to provide a pooled estimate of the prevalence of overall, clinical, and subclinical mastitis in dairy cattle in Ethiopia. A pooled estimate was also conducted by potential risk factors. The literature search was restricted to studies published in English language from January 2002 to June 2016. Meta-analysis of 39 studies was done under random effects model using metafor package in R software. The pooled estimate of the overall prevalence of mastitis on cow-basis was found to be 47.0% (95% confidence interval [CI] = 42.0, 52.0). The pooled prevalence with the 95% CI for clinical and subclinical mastitis was 8.3% (95% CI = 6.5, 10.3) and 37% (95% CI = 32.9, 40.7) respectively. There is a statistically significant and high heterogeneity of the prevalence estimates between published studies. The odds of occurrence of mastitis were higher in cows at early (odds ratio [OR] = 1.6; 95% CI = 1.4, 1.8) and late lactation (OR = 1.3; 95% CI = 1.2, 1.5) than mid lactation, in cows with 3-4 (OR = 1.5; 95% CI = 1.4, 1.7) and > 4 parity number (OR = 2.9; 95% CI = 2.6, 3.4) than those with 1-2 parity number. Previous history of mastitis, floor type, milking hygiene, and udder injury had also statistically significant effect on pooled prevalence of mastitis (P < 0.05). The present study reported that there is high prevalence of mastitis in dairy cows in Ethiopia, which could contribute to the low productivity in lactating cows. The statistically significant association of risk factors such as floor type, milking hygiene, and presence of udder injury with mastitis may suggest that dairy farmers can reduce the occurrence of the disease by improving their management practices.