Haemorrhages in the muscles of broiler chickens are major quality defects which occur in all types of muscles and muscle parts. They are closely related to muscle injury and can be the result of trauma, strenuous muscle activity, exposure to extreme environmental conditions, restraining and electrical stunning. In this review the different types of haemorrhages are classified. A brief introduction on muscle morphology and blood supply is given to discuss the mechanisms that may cause haemorrhages and a survey of these mechanisms is presented. Some of the mechanisms, together with factors likely to affect the susceptibility of chickens to haemorrhages, are discussed in relation to rearing, transport, slaughter and processing of broiler chickens.
