This review analyzes the main anatomical structures and neural pathways that allow the generation of autonomous and behavioral mechanisms that regulate body heat in mammals. The study of the hypothalamic neuromodulation of thermoregulation offers broad areas of opportunity with practical applications that are currently being strengthened by the availability of efficacious tools like infrared thermography (IRT). These areas could include the following: understanding the effect of climate change on behavior and productivity; analyzing the effects of exercise on animals involved in sporting activities; identifying the microvascular changes that occur in response to fear, pleasure, pain, and other situations that induce stress in animals; and examining thermoregulating behaviors. This research could contribute substantially to understanding the drastic modification of environments that have severe consequences for animals, such as loss of appetite, low productivity, neonatal hypothermia, and thermal shock, among others. Current knowledge of these physiological processes and complex anatomical structures, like the nervous systems and their close relation to mechanisms of thermoregulation, is still limited. The results of studies in fields like evolutionary neuroscience of thermoregulation show that we cannot yet objectively explain even processes that on the surface seem simple, including behavioral changes and the pathways and connections that trigger mechanisms like vasodilatation and panting. In addition, there is a need to clarify the connection between emotions and thermoregulation that increases the chances of survival of some organisms. An increasingly precise understanding of thermoregulation will allow us to design and apply practical methods in fields like animal science and clinical medicine without compromising levels of animal welfare. The results obtained should not only increase the chances of survival but also improve quality of life and animal production.

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

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RESUMENObjetivo. Evaluar los efectos del estrés agudo debido al manejo y captura sobre los parámetros hematológicos y bioquímicos en bagre de canal (Ictalurus punctatus) bajo cultivo. Materiales y métodos. Los peces (200 g promedio) fueron mantenidos en tanques de cultivo y divididos en dos tratamientos, por duplicado, (n= 15 x 2 x 2 = 60 peces). Treinta bagres fueron expuestos por 5 min a estrés agudo (TE) por manejo y captura, mientras que otro grupo no (grupo control, TnE). Diez peces de cada tratamiento fueron colectados a las 0, 6, y 24 h post-estrés para la extracción de sangre, los bagres del TnE fueron anestesiados durante su manejo y captura. Se evaluó el hemograma (método manual) y bioquímica sanguínea (espectrofotometría). Los resultados fueron analizados mediante la prueba de t student. Resultados. El contenido de eritrocitos, hematocrito, hemoglobina y glucosa de los animales TE fue significativamente mayor (p<0.05) a las 6 h post-estrés en comparación de TnE. Las células inmune en peces TE disminuyeron a las 6 y 24 h post-estrés, siendo leucocitos y linfocitos significativamente menores en el TnE (p<0.05) a las 24 h post-estrés. Otros parámetros evaluados no presentaron diferencias significativas en lo largo del estudio. Conclusiones. Los resultados sugieren que varios indicadores hematológicos y bioquímica sanguínea en los peces son alterados por el estrés agudo ocasionado por manejo y captura.Palabras clave: Bagre, bioquímica sanguínea, estrés, valores hematológicos (Fuente:CAB). ABSTRACTObjetive. Evaluation of hematological and biochemical parameters of culture channel catfish (Ictalurus punctatus) under acute stress by management and capture practice. Materials and methods. Fish (200 g mean) were maintained in culture tanks and divided in two treatments, in duplicate, (n=15x2x2=60 fishes). Thirty catfish were exposed for 5 min to acute stress (TE) by management and capture practice, while other group not (control group, TnE). 10 fish for treatment were collected at 0, 6, and 24 h post-stress for blood collection, where TnE fishes were anesthetized along work. Complete blood count (manual method) and blood biochemical (spectrophotometry) of fish samples were evaluated and their results were analyzed using a Student's t-distribution. Results. The 5346 REVISTA MVZ CÓRDOBA • Volumen 21(2) Mayo -Agosto 2016 erythrocytes, hematocrit, hemoglobin and glucose level of TE animals was significantly higher (p<0.05) at 6 h post-stress, in comparison of TnE. Immune cells in fish TE decreased at 6 and 24 h post-stress, where leukocytes and lymphocytes were significantly lower that TnE (p < 0.05) at 24 h post-stress. Other evaluated parameters did not show significant differences along this study. Conclusions. Those results suggest that several hematological and blood biochemical parameters in fish changed by acute stress generated by management and capture practice.

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