Study of some Factors Influencing the Occurrence of Subclinical Mastitis in Dairy Cattle in Western Algeria

Subclinical mastitis is an insidious disease of the mammary gland that negatively affects the production of the dairy cow. It is necessary to make a diagnosis in order to control them. The main objective is to determine the prevalence of subclinical mastitis and to identify the main risk factors related to the establishment of mammary infections, particularly subclinical mastitis with multi-resistant Staphylococcus in cattle farms in the region of Sidi-Bel-Abbès. The secondary objectives are to describe the characteristics related to the conduct and hygiene of milking that may increase the risk of intramammary infections. A total of 134 cows aged between 1 and 9 years, of Local Breed (n=3), Crossbreed (n= 84) and Holstein Breed (n=47) in different stages of lactation. Milk samples collected from study cows were subjected to California Mastitis Test (CMT) for each udder quarter milk sample.  All animals were clinically examined using a standardized questionnaire in an exhaustive manner and completed in real-time, interviewing the staff in charge of the farms and attending all stages of milking. All dairy cows were apparently healthy with clinically sound udder secreting apparently normal milk. The California Mastitis Test (CMT) was used to analyze the raw milk samples collected. The risk factors studied were either animal-related such as age, breed, lactation rank, stage of lactation (Early, Middle, Late) and parity, or environmental related such as season and collection area. Our results indicate that the prevalence of mastitis in crossbred cows (62.68%) and Holstein cows (35.07%) was significantly higher than that of homebred cows (2.23%) with a clear predominance at the age of 1 to 4 years. The result of CMT performed in the present study showed that the prevalence of subclinical mastitis in udder quarters was significantly higher in crossbred cows 204 (30.72%) than in Holstein cows 124 (36.9%) and local cows 8 (2.38%) respectively. The frequency of udder infections by Staphylococcus increases for both primiparous and multiparous women. The analysis of variance shows that the occurrence of subclinical mastitis is influenced by the stage of lactation especially in early lactation compared to other stages (p < 0.001) and parity (p=0.041) in crossbred cows. The Bacteriology was significantly influenced by stage of lactation (p=0.031), breed (p= 0.017) and season (p= 0.005), respectively. The frequency of mammary infections by Staphylococcus is increasing in both primiparous and multiparous cows. By comparing the sampling areas we can deduce that the western area of the region can be considered as a risk indicator compared to the northern area while the other two areas are not. On the other hand, the association of the two factors, i.e. stage of lactation and sampling zone, the risk of the western zone becomes insignificant (p=0.07) while the middle of the stage of lactation persists as a non-risk phase. The present study allowed us to evaluate the frequency of subclinical mastitis and to identify the different bacterial strains of staphylococci responsible. In Conclusion, determining the risk factors for the development of Subclinical Mastitis allows us to establish a control program to improve the health of the udder of dairy cows and thus increase milk production.