Abstract: Small mammals usually show physiological adaptations to cope with seasonal changes in food quality. To examine the adaptive strategy in energy metabolism of Niviventer lotipes responding to varying dietary quality, we acclimated Niviventer lotipes to high-fiber standard rabbit pellets for 4 weeks with a group of animals fed with standard rat pellets as control. Body mass, parameters of energy intake, and expenditure were measured during the experiment. At the end of the experiment, animals were sacrificed to analyze the body composition. The results show that body mass of Niviventer lotipes fed with rabbit pellets decreased continuously and reached 62. 8% of that in control at the end of the experiment. Basal metabolic rate and nonshivering thermogenesis decreased significantly to 55. 1% and 63. 4% of the control respectively after the food treatment of 4 weeks. Food intake, digestive energy, and apparent digestibility also decreased to 63. 7%, 38. 8%, and 71. 8% of that in control, respectively. Body composition analysis showed that the mass and/or length of most vital organs and digestive tracts significantly decreased in animals fed with high-fiber rabbit pellets. Taken together, apparent digestibility decreased in Niviventer lotipes fed with a high-fiber diet, however, neither the mass/length of digestive tracts nor food intake increased to compensate for the decrease in digestive efficiency. Although the basal metabolic rate and nonshivering thermogenesis were down-regulated in animals fed with rabbit pellets, the energy balance cannot be maintained thus the body mass decreased significantly. This might be explained by the low selection pressure related to the utilization of a high-fiber food in the subtropical habitats of Niviventer lotipes.

Key words: Energy budget, Basal metabolic rate, Nonshivering thermogenesis, Apparent digestibility, Digestive tract

摘要： 自然界中食物质量常存在季节性变化，可影响小型哺乳动物的生理特征及其生存和分布。为研究高纤维(低质量)食物对栖息于贵州遵义的海南社鼠(Niviventer lotipes)能量代谢的影响，通过饲喂标准兔饲料(高纤维)或鼠饲料(低纤维)处理海南社鼠4周，实验期间测定动物的体重和能量摄入，使用开放式代谢仪测定动物的能量消耗，并在实验处理结束后解剖动物进行身体成分分析。研究发现，饲喂兔饲料的海南社鼠实验期间体重持续下降，到实验结束时为饲喂鼠饲料动物(对照组)体重的62.8%。饲喂兔饲料4周后，动物的整体基础代谢率和非颤抖性产热显著下降，分别为对照组的55.1%和63.4%。饲喂兔饲料的海南社鼠干物质摄入、消化能和消化率显著降低，分别为对照组的63.7%、38.8%和71.8%；身体成分分析显示，主要内脏器官重量以及消化道的重量和长度也显著下降。研究结果表明，饲喂高纤维的兔饲料后海南社鼠没有增加食物摄入来补偿消化率的下降，消化道形态尤其是小肠和盲肠的重量和长度没有适应性增加，虽然动物可通过降低基础代谢率和非颤抖性产热节约能量，但动物能量利用效率太低不能维持能量平衡而体重显著下降，海南社鼠对高纤维食物较差的适应性，可能与其在亚热带分布对高纤维食物利用的选择压力较小有关。

关键词: 能量收支, 基础代谢率, 非颤抖性产热, 表观消化率, 消化道