Bacteriological Load in Milk and Prevalence of Selected Diseases of Intensification in Addis Ababa Dairy Farms
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2008-06
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Abstract
A cross sectional investigation of the bacteriological quality of milk and the prevalence of selected diseases of intensification was carried out on 31 intensive farms which were selected as clusters. Data was collected using questionnaire survey, farm observation, clinical examination, CMT, bacterial count, comparative intradermal tuberculin test and milk ring test. The results of this study showed that none of the modern farms (n=31) kept records except one farm. All except three farms were poorly drained and less hygienic. Univariate ANOVA indicated that there was no significant variation observed in the mean log cfu/ml of SPC between the different categories of hygienic practices, availability of potable water and herd size (p>0.05). Herd level prevalence of clinical and subclinical mastitis was 38.75% and 100%, respectively. The prevalence of subclinical mastitis at quarter, cow and herd level was 83.03% (n=1042), 81.8% (n=327) and 100% (n=31), respectively. The prevalence of clinical mastitis at quarter, cow and herd was 3.4% (n=52), 6.5% (n=26) and 38.7% (n=12), respectively. Moreover, 7% of cows were with at least one blind teat and the quarter level teat blindness is 2.81%. Quarter level clinical mastitis was significantly associated with parity number (p<0.05), udder hygiene (p<0.05), farm hygiene (p<0.05), stage of lactation (p<0.05) and herd size (p<0.001) while only parity (p<0.05), stage of lactation (p<0.01) and herd size (p<0.001) were significantly associated to sub-clinical mastitis. The highest prevalence of quarter level clinical mastitis was observed in early (1.6%, n = 16) and late parities (1.5%, n =24), in cows with poor udder cleanliness (2.13%, n =34), in farms with poor hygiene (2.0%, n =32), at late lactation stage (1.8%) and in farms with herd size ranging from 26 to 40 (1.56%, n= 6). On the other hand, the prevalence of subclinical mastitis significantly increased with parity number and stages of lactation and the highest quarter level prevalence was observed in the herd size ranging from 26-40. On the other hand, the overall prevalence of bovine tuberculosis was 62.66% and the disease occurred in significantly higher rates in herds with larger number of animals, in farms with poor ventilation and in cows with 3 and 4 parities. But, age, sex and stage of lactation had no significant association with the prevalence of the disease in the present study. The results of multivariate logistic regression showed that infection of cows by bovine tuberculosis was more of the function of herd size and the ventilation status. The prevalence of bovine brucellosis was 12.9% (n=4) and there was significant association between the herd level prevalence of bovine brucellosis and the abortion
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history in the herds. On account of these results it is concluded that bacterial quality of raw milk produced and marketed by intensive dairy farms in Addis Ababa is of inferior quality and possible risk to public health from zoonotic diseases. Therefore, it is recommended that national milk quality standards and regulations demarcating the minimum operational environments of the routine husbandry practices and health requirements of dairy animals should be instituted.
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Bacterial load, Bovine brucellosis, Dairy farms, Intensive system, Bovine mastitis, Milk quality, Bovine tuberculosis