A group level analysis of the associations between antibodies to seven putative pathogens and respiratory disease and weight gain in Ontario feedlot calves.
In 14 groups of feedlot calves, housed in 2 feedlots in pens of 3-8 animals, seroconversion rates to pathogens associated with respiratory disease in cattle were assessed for their possible predictive value for respiratory disease. The reactions to Pasteurella haemolytica (Ph) surface antigens, Ph cytotoxin (Ph cytox), infectious bovine rhinotracheitis virus, bovine virus diarrhoea virus (BVDV), parainfluenza-3 virus (PIV3), respiratory syncytial virus, Mycoplasma dispar (Md) and M. bovis (Mb) were studied. Seroconversion rates to BVDV and Mb were predictive of increased respiratory disease rates, and seroconversion rates to Ph, Ph cytox, Md and PIV3 were predictive of decreased weight gains. Serological titre was not predictive of relapse rate. It is suggested that studies such as these, evaluated at group level, rather than individual calf level, may help to elucidate the aetiology of bovine respiratory disease.