In vitro antimicrobial inhibition profiles of Mycoplasma bovis isolates recovered from various regions of the United States from 2002 to 2003

Mycoplasma bovis Infections in young calves

Mycoplasma bovis has emerged as an important pathogen of young intensively reared calves in North America. A variety of clinical diseases are associated with M bovis infections of calves, including respiratory disease, otitis media, arthritis, and some less common presentations. Clinical disease associated with M bovis often is chronic, debilitating, and poorly responsive to antimicrobial therapy. Current control measures are centered on reducing exposure to M bovis through contaminated milk or other sources, and nonspecific control measures to maximize respiratory defenses of the calf. This article focuses on the clinical and epidemiologic aspects of M bovis infections in young calves.

Mycoplasma bovis pneumonia in cattle

Mycoplasma bovis is an important and emerging cause of respiratory disease and arthritis in feedlot cattle and young dairy and veal calves, and has a variety of other disease manifestations in cattle. M. bovis is certainly capable of causing acute respiratory disease in cattle, yet the attributable fraction has been difficult to estimate. In contrast, M. bovis is more accepted as a cause of chronic bronchopneumonia with caseous and perhaps coagulative necrosis, characterized by persistent infection that seems poorly responsive to many antibiotics. An understanding of the disease has been recently advanced by comparisons of natural and experimentally induced disease, development of molecular diagnostic tools, and understanding some aspects of virulence, yet uncertainties regarding protective immunity, the importance of genotypic diversity, mechanisms of virulence, and the role of co-pathogens have restricted our understanding of pathogenesis and our ability to effectively control the disease. This review critically considers the relationship between M. bovis infection and the various manifestations of the bovine respiratory disease complex, and addresses the pathogenesis, clinical and pathologic sequelae, laboratory diagnosis and control of disease resulting from M. bovis infection in the bovine respiratory tract.

Board-invited review: recent advances in management of highly stressed, newly received feedlot cattle

Morbidity and mortality from bovine respiratory disease (BRD) and associated losses in performance and carcass merit continue to plague the beef cattle industry. Several viral/bacterial agents are responsible for BRD, and interactions occur among the agents. Viral agents often predispose animals to bacterial infections, and Mannheimia haemolytica is the most frequently isolated organism in cattle with BRD. Laboratory tests are available to characterize organisms causing BRD using easily obtained nasal swab samples. Testing for persistent infection with bovine viral diarrhea virus can be done by a 2-stage technique using PCR and immunohistochemistry. Preconditioning programs that include preweaning viral vaccination programs along with castration could have a significant influence on decreasing BRD in the cattle feeding industry. Metaphylactic antibiotic programs continue to be effective; however, antibiotic resistance is a public concern, and additional management options (e.g., direct-fed microbials or other compounds with antimicrobial properties) deserve attention. Diets with an increased energy concentration achieved by decreasing the dietary roughage concentration may slightly increase the rate of BRD morbidity; however, these diets also increase ADG, DMI, and G:F compared with lower-energy, greater-roughage diets. The extent to which performance and BRD morbidity are affected by dietary protein concentration needs further study, but low and high protein concentrations should probably be avoided. Several trace minerals (e.g., Cu, Se, and Zn) affect immune function, but the effects of supplementation on performance and immune function in model challenge systems and in field studies are equivocal. Adding vitamin E to receiving diets at pharmacological levels (e.g., >1,000 IU x animal(-1) x day(-1)) seems beneficial for decreasing BRD morbidity, but it has little effect on performance. Given the limited ability to consistently modify immune function and BRD morbidity through dietary manipulations, we recommend that the diets for newly received cattle be formulated to adjust nutrient concentrations for low feed intake and to provide optimal performance during the receiving period.

Bovine respiratory disease: pathogenesis, clinical signs, and treatment in lightweight calves

No matter what disease is being addressed, there are basic steps required for successful therapy. Failure to address each step systematically leaves a gap in the program that eventually shows up as inconsistency or failure in therapeutic efficacy. The focus in this article is on applying these steps in infectious bovine respiratory disease challenges in lightweight stocker calves.