EVALUATION OF SOME RISKS FACTORS IN BOVINE SALMONELLOSIS

Previous work has given evidence of the frequency of Salmonella carria ge by healthy dairy cows, the increased excretion of Salmonella by tal ent carriers at the calving time, and the frequency of clinical salmon ellosis during that period. From this the authors evaluated the releva nce of 3 risks factors supposed to play a role in the triggering clini cal salmonellosis, namely: metabolic and hepatic parameters; Fasciola hepatica infestation; and bovine virus diarrhoea (BVD) infection. The prevalence of F hepatica and BVD, identical in infected and control he rds, suggested that flukes and BVD did not play a significant role in the development of salmonellosis in the conditions of the present work . Although the mean values of metabolic and hepatic parameters were no t different between healthy animals within infected herds and controls , the sequential monitoring performed in 2 reference herds gave eviden ce of important modifications at the calving time and during the early stages of milk production. If not formally demonstrated in this study , it is suggested that metabolic and hepatic changes observed during t he peripartum, could result in a disruption of the intestinal ecosyste m (pH, volatile fatty acids, NH3, peristaltism) and in the emergence o f a Salmonella population. The excretion of considerable amounts of Sa lmonella by the first sick animals allows it to spread to the others, especially those with impaired hepatic functions.