Bovine respiratory disease complex

Abstract

Respiratory disease is the principal cause of loss of young cattle worldwide. The syndrome arises from a number of factors, including those involving the animal, e.g., age, general condition and immune status; its environment, e.g., changes in food, temperature and humidity that lead to stress; and the presence of infectious agents, e.g., bacteria, viruses and mycoplasmas. The syndrome, in a method preferred by the author, can be classified into four grades; Grade 1, subclinical disease; Grade 2, compensated clinical disease (at this stage, the inflammatory reaction generated tends to limit the impact of the disease on the animal); Grade 3, noncompensated clinical disease (at this stage, the inflammatory reaction is excessive and must be controlled); and Grade 4, irreversible clinical disease (which threatens the animal's survival). The increase in frequency and economic impact of bovine respiratory disease complex can be correlated with the escalating industrialization of cattle production. In intensive operations, commingling of animals from multiple sources, exposure to many organisms, stress and management practices are all factors that can lead to disease. The predisposition of cattle, especially beef calves, to respiratory problems is related to their lack of functional pulmonary hardiness. Selection of breeds that demonstrate adequate pulmonary function and sufficient ventilatory reserve may help in the control of the bovine respiratory disease complex, hut this approach is difficult to implement and slow to produce results. Prophylactic measures, including vaccination programs and modifying management practices to reduce stress, also have a place in preventing the bovine respiratory disease complex. Unfortunately, these measures are not always easy to put into operation and cannot completely eradicate the problem. Therapeutic strategies to minimize the economic impact of the syndrome include use of appropriate antibacterial therapy, modulation of the pulmonary inflammatory reaction and correction of mechanical disorders.