RUMINANT NUTRITION SYMPOSIUM: Ruminant Production and Metabolic Responses to Heat Stress
RUMINANT NUTRITION SYMPOSIUM: Ruminant Production and Metabolic Responses to Heat Stress
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DOI：
10.2527/jas.2011-4675
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发表时间：
2012-06-01
影响因子：
3.3
通讯作者：
Rhoads, R. P.
中科院分区：
文献类型：
--
作者：
Baumgard, L. H.;Rhoads, R. P.
热应激通过边缘化营养、管理和遗传选择努力来最大限度地提高性能终点，从而损害了有效的动物生产。改造农场基础设施在减轻热应激相关损失方面取得了一定的成功，但夏季产量低下仍然是畜牧业生产者面临的最昂贵的问题。减少输出（例如，产奶量和肌肉生长）传统上认为是由于营养摄入减少（即，在环境诱导的体温过高期间所有动物共有的经典生物反应）。我们最近的观察已经开始挑战这一信念，并表明热应激动物采用新的顺势策略来指导代谢和燃料选择优先级，而不依赖于营养摄入或能量平衡。全身生理学的改变支持碳水化合物代谢的转变，基础和刺激循环胰岛素浓度增加是明显的。考虑到热应激动物的能量不足，也许最有趣的是明显缺乏基础脂肪组织动员，加上对脂解刺激的反应性降低。因此，热应激反应显着改变吸收后的碳水化合物，脂质和蛋白质代谢的独立减少饲料摄入量通过协调变化的燃料供应和利用的多个组织。有趣的是，系统的，细胞的，和分子的变化似乎保守之间的不同物种和生理状态。最终，这些变化导致在热应激期间燃料选择的重新优先化，这似乎是在温暖的夏季月份期间反刍动物生产力降低的主要原因。
Heat stress compromises efficient animal production by marginalizing nutrition, management, and genetic selection efforts to maximize performance endpoints. Modifying farm infrastructure has yielded modest success in mitigating heat stress-related losses, yet poor production during the summer remains arguably the costliest issue facing livestock producers. Reduced output (e.g., milk yield and muscle growth) during heat stress was traditionally thought to result from decreased nutrient intake (i.e., a classic biological response shared by all animals during environmental-induced hyperthermia). Our recent observations have begun to challenge this belief and indicate heat-stressed animals employ novel homeorhetic strategies to direct metabolic and fuel selection priorities independently of nutrient intake or energy balance. Alterations in systemic physiology support a shift in carbohydrate metabolism, evident by increased basal and stimulated circulating insulin concentrations. Perhaps most intriguing given the energetic shortfall of the heat-stressed animal is the apparent lack of basal adipose tissue mobilization coupled with a reduced responsiveness to lipolytic stimuli. Thus, the heat stress response markedly alters postabsorptive carbohydrate, lipid, and protein metabolism independently of reduced feed intake through coordinated changes in fuel supply and utilization by multiple tissues. Interestingly, the systemic, cellular, and molecular changes appear conserved amongst different species and physiological states. Ultimately, these changes result in the reprioritization of fuel selection during heat stress, which appears to be primarily responsible for reduced ruminant animal productivity during the warm summer months.