We examined the pathogens, morphologic patterns, and risk factors associated with bovine respiratory disease (BRD) in 136 recently weaned cattle ("weanlings"), 6-12 mo of age, that were submitted for postmortem examination to regional veterinary laboratories in Ireland. A standardized sampling protocol included routine microbiologic investigations as well as polymerase chain reaction and immunohistochemistry. Lungs with histologic lesions were categorized into 1 of 5 morphologic patterns of pneumonia. Fibrinosuppurative bronchopneumonia (49%) and interstitial pneumonia (48%) were the morphologic patterns recorded most frequently. The various morphologic patterns of pulmonary lesions suggest the involvement of variable combinations of initiating and compounding infectious agents that hindered any simple classification of the etiopathogenesis of the pneumonias. Dual infections were detected in 58% of lungs, with Mannheimia haemolytica and Histophilus somni most frequently recorded in concert. M. haemolytica (43%) was the most frequently detected respiratory pathogen; H. somni was also shown to be frequently implicated in pneumonia in this age group of cattle. Bovine parainfluenza virus 3 (BPIV-3) and Bovine respiratory syncytial virus (16% each) were the viral agents detected most frequently. Potential respiratory pathogens (particularly Pasteurella multocida, BPIV-3, and H. somni) were frequently detected (64%) in lungs that had neither gross nor histologic pulmonary lesions, raising questions regarding their role in the pathogenesis of BRD. The breadth of respiratory pathogens detected in bovine lungs by various detection methods highlights the diagnostic value of parallel analyses in respiratory disease postmortem investigation.

BackgroundDelaying pigs from advancing through the production stages could have a negative impact on their health and performance. The objective of this study was to investigate the possible implications of delaying pigs from the normal production flow on pig health and performance in a farrow-to-finish commercial farm with a self-declared All-In/All-Out (AIAO) management.ResultsThree flows of pigs were defined, flow 1 (i.e. pigs that followed the normal production flow; 8 weeks in the nursery stage, 4 weeks in the growing stage and 8 weeks in the finisher stage), flow 2 (i.e. pigs delayed 1 week from advancing to the next production stage) and flow 3 (i.e. pigs delayed >1 week from advancing to the next production stage). Flow 3 included higher proportions of pigs from first parity sows and of lighter birth weights. When the 3 flows were matched by parity and birth weight, pigs in flow 2 were 3.8 times more likely to be lame prior to slaughter compared with pigs in flow 1. Similarly, pigs in flow 3 were more likely to be lame prior to slaughter, 4.5 times more likely to present pleurisy, 3.3 times more like to present pericarditis and 4.3 times more likely to have their heart condemned at slaughter compared with pigs in flow 1. Additionally, carcasses from pigs in flow 3 were 10 kg lighter compared with carcasses from pigs in flow 1.ConclusionDelayed pigs were more affected by disease and were lighter at slaughter. Besides animal welfare issues, these findings could represent considerable economic loses for pig producers. In practice, delaying pigs from the normal production flow translates into higher feeding costs, increase number of days to slaughter and increased labour requirements reducing production efficiency for the pig operation. In farrow-to-finish farms an ‘all-forward’ policy (i.e. no pig is left behind from stage to stage and a split marketing approach is applied when sending pigs to slaughter) might be more easily adhered to.

Bovine respiratory disease (BRD) is one of the most commonly diagnosed causes of morbidity and mortality in cattle and interactions of factors associated with the animal, the pathogen and the environment are central to its pathogenesis. Emerging knowledge of a role for pathogens traditionally assumed to be minor players in the pathogenesis of BRD reflects an increasingly complex situation that will necessitate regular reappraisal of BRD pathogenesis and control. This review appraises the role of selected key pathogens implicated in BRD pathogenesis to assess how our understanding of their role has evolved in recent years.