Respiratory function in cattle: impact of breed, heritability and external factors.

Abstract

Bovine respiratory disease complex (BRDC) is the most common and costly disease of cattle. The important prevalence of this multifactorial syndrome results from interactions between different pathogens, physical constitution of the host and environmental factors. Because of the strong economical impact of BRDC, it is recommended to complete classical preventive and therapeutic measures by selection of heritable traits improving resistance against respiratory disease and by alternatives based on improved control of environmental factors. The transport of oxygen between the atmospheric air and the mitochondria essentially includes four steps, i.e. (1) respiratory function, including pulmonary ventilation, perfusion and respiratory mechanics, (2) blood circulation and oxygen transport, (3) capillary-cell diffusion and (4) oxygen combustion by mitochondria. Each step should be considered when factors improving resistance against respiratory disease are investigated. This review aims (1) to summarise briefly the anatomical, histological and physiological peculiarities of the bovine respiratory system and (2) to consider the effect of breed, heritability and external factors at each step of the oxygen transport chain, by focussing essentially on respiratory function.