Influência da restrição alimentar e do estresse térmico sobre parâmetros fisiológicos em ovinos / [Influence of food restriction and heat stress on physiological parameters in sheep]

Objetivou-se avaliar as alterações fisiológicas de ovinos submetidos à restrição alimentar, expostos à radiação solar e à sombra. Dez borregas mestiças foram divididas igualmente em dois grupos: grupo radiação solar - GRS, animais expostos ao sol durante o dia; e grupo sombra - GS, animais alocados dentro de um galpão à sombra. Nos seis dias iniciais de experimento, os animais foram submetidos à restrição alimentar, com acesso apenas à água, já expostos ao sol ou à sombra. Nos seis dias subsequentes, foi ofertada dieta composta por ração e feno de alfafa (3%PV). Os parâmetros avaliados foram frequência respiratória (FR), temperatura retal (TR), ß-hidroxibutirato (BHB), pH urinário, ingestão de matéria seca (IMS) e dados bioclimáticos (temperatura, umidade relativa do ar e índice de temperatura e umidade - ITU). A FR foi o parâmetro em que houve maior diferença significativa entre os grupos (p<0,05). O balanço energético negativo foi constatado em todos os animais (BHB>0,8mmol/L; pH<7,0). Ovelhas que sofrem restrição alimentar durante períodos de alta temperatura e umidade têm menor frequência respiratória e temperatura interna, independentemente de estar na sombra ou pleno sol. Porém, quando normalizado a oferta de alimento as ovelhas em pleno sol têm menor ingestão de matéria seca.(AU)

We aimed to evaluate physiological changes in sheep submitted to food restriction, exposed to the sun or shade. Ten ewe lambs were equally divided into two groups: Sun Radiation Group - GRS, exposed to sun during day hours, and Shade Group - GS, with animals placed inside a barn. In the first six days of experiment, animals were submitted to food restriction, with access to fresh water, already exposed to sun and shade. In the following six days alfalfa hay and concentrate were provided to the animals (3%BW). Parameters assessed were respiratory rate (FR), rectal temperature (TR), ß-hydroxybutyrate, urinary pH, dry matter intake (IMS) and climate data (air temperature, humidity, and temperature-humidity index - ITU). The parameter that most differed between groups was FR. All animals presented negative energy balance (BHB>0.8mmol/L; pH<7,0). Ewe lambs submitted to food restriction during periods of high temperature and humidity have lower respiratory rate and intern temperature, independently of being exposed to sun or shade. However, when food was offered animals exposed to sun had lower dry matter intake.(AU)

Effect of pentoxifylline on the regeneration of rat testicular germ cells after heat shock

High temperature is an important factor for reproduction and can induce testicular degeneration. Pentoxifylline is a methylxanthine phosphodiesterase inhibitor with anti - inflammatory and anti - apoptotic properties. Considering the protective propert ies of pentoxifylline and the harmful effects of heat, the present study aimed to use pentoxifylline to reduce the damage induced by heat to the testis. Adult mal e Wistar rats were exposed to testicular heat shock (43ºC for 15 min) , treated with 50 or 100 mg/ k g of pentoxifylline and evaluated at 3, 7, 15, 30 and 60 days after heat shock. Pentoxifylline treatment did not change testicular weight, histomorphometrical parameters or plasma testosterone concentration. However, pentoxifylline inhibited germ cell apoptosis and reduced the severity of pathological lesions at 30 and 60 days after testicular heat shock. In conclusion, pentoxifylline treatment seem ed to inhibit pro - inflammatory and apoptotic mechanisms triggered by testicular heat shock, improving sper matogenesis regeneration.

Sublethal temperature stress in juvenile Labeo rohita (Ham-Buch.) and Rita rita (Ham.): some physiological changes.

Juveniles of fish L. rohita and R. rita subjected to a rapid (5 min) sublethal temperature increase from 28 to 35 degrees C showed significant increase in cortisol and decrease in interrenal ascorbic acid. Hypercholesterolemia, hyperglycemia and hyperlactemia were also evident accompanied by increased blood haemoglobin and haematocrit and stable protein levels. Compensatory responses were initiated within 72 hr in both the fishes. R. rita recovered more quickly indicating it to be more resistant to the heat stress than L. rohita. Hence fishes subjected to sublethal temperature stress should be given a metabolic recovery period of 72 hr prior to further stress being applied.

Human heat tolerance in simulated environment.

The heat tolerance of 11 male volunteers were examined under seven climatic conditions in a climatic chamber. The conditions were 38 to 49 degrees C dry bulb temperature and 45 to 80 per cent relative humidity, i.e., 32.3 to 40 degrees C effective temperature-basic [ET(B)]. The ET(B) values were equated to other heat stress indices, e.g., WBGT (Wet-bulb Globe Temperature Index) and Oxford Index. The subjects did ergometric work at an intensity of 60 per cent VO2max. The exposure durations were decided by the cardiorespiratory, body temperature and sweating responses. Of the climatic conditions studied, at 35.4, 38, 39 and 40 degrees C ET(B), the body core temperature (Tcr) reached over 39 degrees C and heart rates attained 172 to 182 beats/min, which were taken as the tolerance limit. The total oxygen demand significantly varied with the increase in environmental warmth, i.e., increase or decrease of one litre of oxygen demand was equivalent to one minute change in tolerance time. The volunteers were not susceptible to heat; only in extreme hot situations beyond 35.4 degrees C ET(B), were unacceptable levels of physiological and psychophysical reactions seen. The study suggests the acceptable and tolerable limits for human exposure in heat: (i) acceptable at 38 to 38.2 degrees C Tcr for a tolerance time of 80 to 85 min; and (ii) the tolerable limit of short duration (40-45 min) at 39 degrees C Tcr that corresponded to 31.5 and 36.5 degrees C ET(B).