Prevalence and risk factors of subclinical mastitis in lactating dairy cows in north and south regions of Bangladesh
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Prevalence and risk factors of subclinical mastitis in lactating dairy cows in north and south regions of Bangladesh Swapan Chandra Sarker & Mst. Sonia Parvin & A. K. M. Anisur Rahman & Md. Taohidul Islam
Accepted: 17 December 2012 / Published online: 31 December 2012 # Springer Science+Business Media Dordrecht 2012
Abstract The purpose of the study was to identify the potential risk factors for subclinical mastitis (SCM) in lactating dairy cows in Bangladesh. A cross-sectional study was carried out on randomly selected 212 smallholder dairy farms of Sadar upazilas of Rangpur, Mymensingh, and Satkhira districts of Bangladesh during January to October 2011. The direct interview using a structured questionnaire and physical examination of the cows were done to collect data on 15 variables. Milk samples collected from study cows were subjected to California Mastitis Test (CMT). The diagnosis of SCM was based on the results of CMT and physical examination of udder and milk. The bivariable followed by multivariable analysis was done using SPSS 17.0. Of the total cows examined, 20.2 % had subclinical mastitis. In bivariable analysis, eight risk factors were identified. However, in the final model of multivariable analysis, four potential risk factors were identified. These were history of previous clinical mastitis (odds ratio (OR) 10.51, p4–8, and >8 years. Body condition score was categorized as 2–2.5, >2.5–3, and >3. Stage of lactation was categorized as 15–60, >60–120, and >120 days. Parity was categorized as 1–2 calves, 3–4 calves, and ≥5 calves. Milk yield was categorized as 0.5–3, >3–5, and >5 L. The first author, himself a trained veterinarian, was directly involved in the data collection process.
SCM affected cows (n=97)
SCM non-affected cows (n=383)
Mean
Mean
Age (years) 6.5 BCS 2.79 Last lactation age 159.4 (days) Milk yield (L) 7.7
95 % CI
95 % CI
5.96–7.07 5.7 5.44–5.90 2.73–2.85 2.87 2.83–2.90 138.66–180.12 141.6 132.28–150.95 6.87–8.56
7.4
6.97–7.85
Prevalence Of the total 480 lactating cows examined, 20.2 % (97) had subclinical mastitis. Cross-bred cows were affected at higher rate (21.5 %) than local zebu cows (13.8 %). The prevalence of SCM was higher (22.6 %) in late lactation (>120 days) and lower (17.0 %) in early lactation (15–60 days). Older cows (>8 years) were more affected (38.3 %) than younger (2–4 years) cows (16.3 %). Cows with many calves (≥5) were more affected (38.6 %) than those with fewer (1–2) calves (16.6 %).
Statistical analyses
Risk factors
The animal and farm level data were entered into spread sheet program (Microsoft Excel) and transferred into SPSS 17.0 for statistical analysis to estimate the strength and statistical significance of associations between predictor variables and SCM. At first the data were organized for bivariable analysis to find out the effect of individual risk factor on SCM. The variables that resulted p value ≤0.2 in the bivariable analysis were selected as potential candidates for multivariable analysis (multiple logistic regr
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