Risk factors for calf mortality influence the occurrence of antibodies against the pathogens of enzootic bronchopneumonia

Abstract

Bovine respiratory diseases are a common cause of calf loss. This study aimed to analyse associations between an occurrence of enzootic bronchopneumonia (EBP), calf mortality and calving management. A total of 153 dairy farms participated in the study on a voluntary basis from November 2006 to July 2007. Calf management was inspected on-site during a farm visit and farm managers were required to complete a questionnaire on personal assessment of calving procedures, neonate management and environmental factors. Results were collated and matched with the calf mortality rate of 2006 determined from the HI-Tier database for each farm. Randomly selected serum samples of a mean number of 7 calves at the age 6 months per herd were investigated for antibodies against bovine respiratory syncytial virus (BRSV-AB) and parainfluenzavirus type 3 (PIV3-AB). According to the proportion of calves with BRSV-AB or PIV3-AB (≤ 20 % or > 20 %) farms were divided into 2 groups. Customary timing of the first colostrum feeding as well as the perceived level of importance of EBP to the farm manager, as described in the questionnaire, showed a positive correlation to calf mortality. BRSV-AB occurred more frequently on farms where managers stated that the first colostrum feeding occurred later than 4 hours after birth, that birth monitoring was rarely practiced and that the estimated level of dust in the calf barn was considered high. PIV3-AB was more frequently found at farms practicing tethered calving. The results of this study indicate that peri- and postnatal calf management procedures may affect calf mortality and the frequency of occurrence of BRSV-AB or PIV3-AB. The influences of birth monitoring and the time of first colostrum feeding as well as dust exposure should be taken into account in future studies on the frequency of EBP and be included in the veterinary cause analysis of herd EBP-related problems.