Respiratory Affections in Calves in Upper and Middle Egypt: Bacteriologic, Immunologic and Epidemiologic Studies

B respiratory disease (BRD) is considered one of the most common worldwide affections in calves causing huge economic losses due to reduction of feed efficiency, average daily gain, overall performance and finally calf mortality (Härtel et al., 2004; Taylor et al., 2010). The incidence of BRD has been reported with variability from 5 to 66% in feedlot cattle and it is the most costly beef cattle disease (Snowder et al., 2006).