Effect of passive transfer status and vaccination with Escherichia coli (J5) on mortality in comingled dairy calves

The effect of vaccination with a commercially available R-mutant coliform m astitis vaccine on the survival of comingled dairy calves on a farm with en demic salmonellosis was examined. A total of 864 calves were randomly assig ned to either vaccine (n = 435) or control (n = 429) groups. Passive transf er status of each calf was determined using refractometer determination of serum total protein concentration. Logistic models were developed to determ ine the effects of vaccine group and passive transfer status on calf surviv al to 100 days of age, in a model in which serum protein concentration was treated as a categorical variable, increasing serum total protein concentra tions were associated with decreased mortality until these concentrations e xceeded 6.0 g/dL. Calves with serum protein concentrations >6.0 g/dL had in creased risk for mortality compared with calves with serum protein concentr ations >5.5 g/dL but less than or equal to 6.0 g/dL. This increased risk fo r mortality was supported by the results of a logistic model in which serum protein concentration was treated as a continuous variable. The increased risks associated with high serum protein concentration probably reflect the effect of dehydration in calves with occult disease. Neither model demonst rated any significant association between vaccination status and survival t o 100 days of age. Based on these results, the routine immunization of calv es cannot be recommended as a strategy to prevent mortality on farms with e ndemic salmonellosis.