Moe Borge, Stolevik Einar, Bech Claus
Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
Physiol Biochem Zool. 2005 Jan-Feb;78(1):90-104. doi: 10.1086/425199.
We investigated whether Pekin ducklings (Anas platyrhyncos domesticus) exhibited any energy-saving mechanisms that could lessen the detrimental effects of reduced food intake during early development. Further, we evaluated the role of body compositional changes behind such potential mechanisms and the consequences on thermoregulatory capacity. The ducklings exhibited substantial energy-saving mechanisms as a response to diet restriction. After 5 d of diet restriction, the resting metabolic rate (RMR) of 10- and 20-d-old ducklings was 16.4% and 32.1% lower, respectively, than predicted from body mass compared with ad lib. fed ducklings (controls). These reductions in RMR could have been adaptive responses in anticipation of a lasting food shortage, or they could have been consequences of the restricted diet and the lack of essential nutrients. We argue that the responses were adaptive. The low RMRs were not a consequence of depleted fuel stores because the diet-restricted ducklings exhibited substantial amounts of stored lipids at the end of the diet-restriction periods. Hypothermia accounted for approximately 50% of the reduction in RMR in the 10-d-old diet-restricted ducklings, but hypothermia did not occur in the 20-d-old diet-restricted ducklings. Diet restriction resulted in a reduced liver and intestine size and an unchanged size of the leg muscles and heart, while the length of the skull increased (compared with controls of a given body mass). However, changes in body composition were only minor predictors of the observed changes in RMR. Peak metabolic rate (PMR) was approximately 10% lower in the diet-restricted ducklings compared with the controls. We have interpreted the lower PMR as a consequence of the reductions in RMR rather than as a consequence of a decreased function of the thermoregulatory effector mechanisms.
我们研究了北京鸭（Anas platyrhyncos domesticus）是否表现出任何节能机制，这些机制可以减轻早期发育过程中食物摄入量减少的不利影响。此外，我们评估了身体成分变化在这些潜在机制背后的作用以及对体温调节能力的影响。雏鸭表现出了应对饮食限制的显著节能机制。在饮食限制5天后，与自由采食的雏鸭（对照组）相比，10日龄和20日龄雏鸭的静息代谢率（RMR）分别比根据体重预测的低16.4%和32.1%。RMR的这些降低可能是对持续食物短缺的适应性反应，也可能是受限饮食和缺乏必需营养素的结果。我们认为这些反应是适应性的。低RMR并非燃料储备耗尽的结果，因为饮食受限的雏鸭在饮食限制期结束时表现出大量储存的脂质。体温过低约占10日龄饮食受限雏鸭RMR降低的50%，但20日龄饮食受限雏鸭未出现体温过低的情况。饮食限制导致肝脏和肠道尺寸减小，腿部肌肉和心脏尺寸不变，而头骨长度增加（与给定体重的对照组相比）。然而，身体成分的变化只是观察到的RMR变化的次要预测因素。与对照组相比，饮食受限的雏鸭的峰值代谢率（PMR）约低10%。我们将较低的PMR解释为RMR降低的结果，而不是体温调节效应机制功能下降的结果。
