Meta-analysis and meta-regression of subclinical mastitis prevalences of dairy cattle in Turkey

Mastitis is one of the most important problems of the dairy industry because of the economic losses due to decreases in milk yield and in milk quality. Subclinical mastitis is a form of mastitis that has no macroscopic inflammation in the mammary gland and visible change in milk, and approximately 70-80% of milk losses caused by mastitis are due to subclinical mastitis. Many previous studies, screening the mastitis and the isolation and identification of microorganisms in collected milk samples, have been conducted in dairy cattle at the regional level in Turkey. Since many studies have been performed to predict the prevalence of subclinical mastitis and to determine the factors affecting the disease, systematic review or meta-analysis studies on the subject have been required. In this study, it was aimed to determine the prevalence of subclinical mastitis obtained from 38 studies conducted in Turkey between 1988 and 2019 by meta-analysis method and to calculate common prevalence. The estimated prevalence of subclinical mastitis in the studies were evaluated separately as cow-based (11182 cows in 37 studies) and udder quarter-based (48990 udder quarters in 33 studies). According to the results, the common prevalence of subclinical mastitis was calculated as 0.49 (95% CI: 0.41-0.56) in cow-based studies and 0.32 (95% CI: 0.26-0.37) in quarter based- based studies. As a result of this study, the results of individual studies on the prevalence of subclinical mastitis in dairy cows in Turkey were combined with the meta-analysis method and a more precise estimate of the prevalence was obtained.