Quality of Death in Fighting Bulls during Bullfights: Neurobiology and Physiological Responses

Simple Summary Fighting bulls that participate in bullfighting face energy and metabolic demands due to the high intensity and duration of the exercise performed. Under these conditions, specific corporal mechanisms, such as the acid-base balance, are affected, causing metabolic acidosis. However, fighting bulls also undergo muscular injuries, physiological changes, and high enzyme concentrations that reflect the stress to which they are subjected, and in some bulls, bullfights can trigger electrolytic imbalances that include hypercalcaemia, hypermagnesaemia, and hyperphosphataemia, exacerbated by muscular necrosis and myoglobinuria. During bullfights, bulls undergo physiometabolic responses such as glycolysis, anaerobic reactions, cellular oedema, splenic contraction, and hypovolemic shock. The objective of this review article is to present the current knowledge on the factors that cause stress in fighting bulls during bullfights, including their dying process, by discussing the neurobiology and their physiological responses. The literature shows that biochemical imbalances occur during bullfights, including hypercalcaemia, hypermagnesaemia, hyperphosphataemia, hyperlactataemia, and hyperglycaemia, associated with increased endogenous cortisol and catecholamine levels. Creatine kinase, citrate synthase, and lactate dehydrogenase levels also increase, coupled with decreases in pH, blood bicarbonate levels, excess base, partial oxygen pressure, and oxygen saturation. The intense exercise also causes a marked decrease of glycogen in type I and II muscle fibres that can produce myoglobinuria and muscular necrosis. Other observations suggest the presence of osteochondrosis. The existing information allows us to conclude that during bullfights, bulls face energy and metabolic demands due to the high intensity and duration of the exercise performed, together with muscular injuries, physiological changes, and high enzyme concentrations. In addition, the final stage of the bullfight causes a slow dying process for an animal that is sentient and conscious of its surroundings.