The medicine and epidemiology of bovine respiratory disease in feedlots

Abstract

Bovine Respiratory Disease (BRD) results from a complex, multifactorial interaction of stressors, animal susceptibility, and respiratory pathogens. The infectious agents associated with BRD are ubiquitous among cattle populations. Typically, one or a combination of stressors are necessary to initiate BRD. Prevention of BRD should, therefore, address management procedures to minimise stressors. Administration of vaccines against BRD agents may help reduce the incidence of BRD but is unlikely to eliminate the condition. The effectiveness of antimicrobials in the treatment of BRD depends primarily on early recognition and treatment. The use of antioxidant vitamins, minerals or other agents in the prevention and treatment of BRD warrants further research.

Bovine respiratory disease complex associated mortality and morbidity rates in feedlot cattle from southeastern Brazil

“…Hence, since BRD is a multifactorial and multietiological entity that results in the disequilibrium between the defense system of the host, the action of a wide variety of infectious agents, environmental and genetic factors, and stressors [5,7,42], it is likely that this disease entity will contribute significantly to beef cattle morbidity in feedlots throughout Brazil. The elevated incidence of BRD observed during this study can also be associated with the comingling of animals derived from diverse geographical locations and the diet adaptions during entry into feedlots [43]. In addition, these animals were not on any metaphylactic therapy.…”

“…The distance travelled by feedlot cattle was associated with mortality, elevated BRD morbidity, and can serve as a predictor of cattle health and performance [41]. In addition, other factors associated with transported-related mortality, such as weight loss, and the stocking density and time without feed during transport [4,42,43], might have also contributed to the large percentage of trauma mortality observed during this study.…”

Manejo do complexo respiratório bovino em confinamento: Revisão

“…Sinais e lesões são variáveis, podendo ser serosas, hiperêmicas, com edema e exsudato mucopurulento, necrose focal e em casos mais graves, inflamação pseudomembranosa (Cusack et al, 2003). Essas lesões irão possivelmente gerar destruição do epitélio do trato respiratório superior, o que diminui consideravelmente a atividade mucociliar, favorecendo uma broncopneumonia secundária devido à multiplicação bacteriana no pulmão, também prejudica os mecanismos de defesa pulmonar reduzindo migração de neutrófilos, resposta mitogênica linfocitária vascular periférica e atividades funcionais de macrófagos alveolares (Cusack et al, 2003). …”

“…Essa replicação irá provocar bronquite, bronquiolite e alveolite. Na fase aguda da infecção, ocorre proliferação e necrose de células epiteliais bronquiais com destruição generalizada dos cílios e de células ciliadas em pequenos brônquios e bronquíolos, então, o vírus infecta macrófagos alveolares possibilitando a ineficiência da resposta imune inata pulmonar, tornando os animais passíveis de contrair uma infecção bacteriana secundária (Cusack et al, 2003).…”

“…Diversos pesquisadores esclareceram a capacidade do uso da profilaxia de antimicrobianos para a redução da morbidade da CRB, aumentando o desempenho dos bovinos no confinamento (Galyean and Hubbert, 1995, Vogel et al, 1998, Cusack et al, 2003. A via de administração pode ser parenteral ou oral, podendo ser através de alimentos ou água (Taylor et al, 2010).…”