Analysis of the impact of risk factors on the occurrence of subclinical mastitis on dairy cattle farms in eastern Algeria

In order to study the effect of various risk factors on the prevalence of subclinical mastitis, we studied the prevalence of subclinical mastitis in 104 dairy cows (416 udders) from 18 bovine herds in three wilayas in eastern of Algeria using the California mastitis test (CMT) combined with bacteriological analysis. The aim of this research was to determine the effect of 27 risk factors related to the animal, its environment and milking practices on prevalence, as well as the effects of breed, age, stage of lactation, housing and litter type, hygiene level, season, mil production, vacuum level and elimination of first jets on subclinical mastitis frequency. A survey was carried out to collect data on cow numbers, breeds, type of breeding, housing, litter and the level of hygiene in farms, the method of milking and milking practices. The CMT combined with bacteriological examination was performed to detect subclinical mastitis, the Chi 2 test was used to test for difference between the means. Prevalence values were: 24% by CMT vs 17% by bacteriology analysis. Concerning udders, we recorded a rate of 10% vs. 8.7% respectively. The results of the survey show that the Holstein breed is the most exploited and affected (P<0.05). The number of dairy cows varied from 3 to 20 cows. In this study, 56% of cows were raised on farms built of cinder blocks, which had a lower rate compared to farms built of wood and reeds (P<0.001). Animal housing consisting of a concrete floor 33% vs. 36% raised with straw bedding and were more affected (P<0.001), litter is removed only once a day for 13% of cows, which is a factor that predisposes cows to this disease. The frequency is higher during early and late compared to mid-lactation phases (P<0.05); low udder conformation and the right side of udders also had an impact on this disease alongside animal hygiene (P<0.05), and cattle producing more than 12 litres per day were more susceptible (P<0.05). However, the frequency of mastitis was only slightly modified by the lactation number of cows. High and low vacuum level of milking machines and pulsation frequency predisposed cows more to this disease (P<0.05). In this study, cows milked manually were significantly more affected (P<0.05) particularly in summer and the winter, showing high rates (P<0.05).