Chauhan S S, Celi P, Leury B J, Clarke I J, Dunshea F R
Department of Animal Husbandry, Government of Himachal Pradesh, Shimla 171005, India Melbourne School of Land and Environment, The University of Melbourne, Parkville, Vic. 3010, Australia
Melbourne School of Land and Environment, The University of Melbourne, Parkville, Vic. 3010, Australia Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2570 Australia.
J Anim Sci. 2014 Aug;92(8):3364-74. doi: 10.2527/jas.2014-7714. Epub 2014 Jun 3.
The present study was undertaken to investigate the impact of heat (thermal) stress and dietary antioxidant supplementation on the oxidative and physiological status of sheep. Twenty-four Merino × Poll Dorset crossbred ewes were housed in 1 of 2 climatic chambers (thermoneutral or heat stress) and offered either a control (10 IU vitamin E/kg DM and 0.24 mg Se/kg DM) or high antioxidant (100 IU vitamin E/kg DM and 1.20 mg Se/kg DM) diet. The sheep were exposed to 2 thermal (temperature) treatments (thermoneutral [TN]: 18-21°C and 26-30% relative humidity; and heat stress [HS]: 28-40°C and 40-50% relative humidity) for 2 wk in a single reversal design. After 1 wk of dietary treatment, animals in 1 chamber were subjected to HS for 1 wk, with the temperature being increased to 40°C between 0900 and 1700 h and then maintained at 28°C overnight. Those sheep in the TN group were maintained at 18 to 21°C. Physiological parameters were recorded 4 times a day (0900, 1300, 1700, and 2100 h) and blood samples were collected on d 1 and 7 of heat treatment. Plasma samples and red blood cell lysates were assayed for oxidative stress biomarkers. The thermal treatments were then reversed and the above measures repeated. All measured physiological parameters were elevated (P < 0.001) by thermal treatment. Respiration rate was lower during HS in sheep supplemented with antioxidants as indicated by a diet × temperature × time interaction (P = 0.010). There was 13% decline (P = 0.014) in feed intake of the unsupplemented animals during HS whereas the same was maintained in sheep supplemented with high doses of antioxidants. Plasma reactive oxygen metabolites concentrations were reduced (114 vs. 85 units/dL; P < 0.005) while biological antioxidant potential tended to be increased (3,688 vs. 3,985 μmol/L; P = 0.070) in heat stressed sheep supplemented with antioxidants. The oxidative stress index was 30% lower (P < 0.001) in supplemented sheep (2.16 ± 0.06 arbitrary units) during HS than in unsupplemented sheep (3.12 ± 0.08 arbitrary units). Plasma advanced oxidation protein products tended (P = 0.070) to decrease in antioxidant supplemented heat stressed sheep as compared to their unsupplemented counterparts. It was concluded that heat stress negatively affects the oxidative status of sheep along with the physiological responses and some of these affects can be ameliorated through dietary antioxidants supplementation at supranutritional concentrations.
本研究旨在调查热应激和日粮添加抗氧化剂对绵羊氧化和生理状态的影响。将24只美利奴×波德代杂交母羊饲养在2个气候舱中的1个（中性温度或热应激），并给予对照日粮（10 IU维生素E/kg干物质和0.24 mg硒/kg干物质）或高抗氧化剂日粮（100 IU维生素E/kg干物质和1.20 mg硒/kg干物质）。绵羊在单一反转设计中接受2种温度处理（中性温度[TN]：18 - 21°C，相对湿度26 - 30%；热应激[HS]：28 - 40°C，相对湿度40 - 50%），持续2周。经过1周的日粮处理后，1个舱中的动物接受1周的热应激处理，0900至1700 h温度升至40°C，然后夜间维持在28°C。TN组的绵羊维持在18至21°C。每天记录4次生理参数（0900、1300、1700和2100 h），并在热应激处理的第1天和第7天采集血样。检测血浆样本和红细胞裂解物中的氧化应激生物标志物。然后反转温度处理并重复上述测量。热应激处理使所有测量的生理参数升高（P < 0.001）。日粮×温度×时间交互作用表明，补充抗氧化剂的绵羊在热应激期间呼吸频率较低（P = 0.010）。未补充抗氧化剂的动物在热应激期间采食量下降13%（P = 0.014），而补充高剂量抗氧化剂的绵羊采食量保持不变。补充抗氧化剂的热应激绵羊血浆活性氧代谢物浓度降低（114对85单位/dL；P < 0.005），而生物抗氧化潜力趋于增加（3688对3985 μmol/L；P = 0.070）。热应激期间，补充抗氧化剂的绵羊氧化应激指数比未补充的绵羊低30%（P < 0.001）（2.16 ± 0.06任意单位对3.12 ± 0.08任意单位）。与未补充抗氧化剂的热应激绵羊相比，补充抗氧化剂的热应激绵羊血浆晚期氧化蛋白产物趋于减少（P = 0.070）。研究得出结论，热应激对绵羊的氧化状态以及生理反应产生负面影响，通过超营养浓度的日粮添加抗氧化剂可以改善其中一些影响。
