哺乳动物的消化策略(英文)

DIGESTIVE STRATEGIES OF MAMMALS

理解动物的营养生态位是充分理解其整个生态学的基础 ,对于害兽控制和物种保护也很重要。食肉动物的小肠很发达 ,这可能与对食物的高消化能力有关 ;杂食性动物有更复杂的胃肠器官 ,其后端有可进行发酵的盲肠 ,消化物的平均滞留时间 (meanretentiontimes ,MRTs)更长 ;最长的平均滞留时间见于食草动物 ,其消化道内高密度的微生物种群对不同滞留区内的消化物进行发酵。但是 ,并不是所有的食草动物都能够最大程度地消化植物纤维 ,只有反刍动物、骆驼和个体较大的后肠发酵动物 (hindgutfermenter)能够具有这种能力。对比而言 ,许多其它的食草动物 ,如前肠发酵的有袋类和小型的后肠发酵动物如兔子、田鼠和负鼠等 ,它们具备可以使植物纤维消化效率最大的消化系统 ,可以在食物中的纤维素含量非常高的情况下仍能处理大量的食物。

Understanding an animal's nutritional niche is fundamental to a full appreciation of its ecology, and is important for both pest control and species conservation purposes. Carnivores have digestive systems dominated by the small intestine, which can be related to the generally high digestibility of their food. Omnivores have more complex gastrointestinal tracts, with a hindgut caecum in which some microbial fermentation takes place, and they have longer mean retention times (MRTs) of digesta. The longest MRTs are found in herbivores, in which digesta are retained and fermented by dense microbial populations in one or more regions of relative stasis. However, not all herbivores have digestive systems that maximise fibre digestibility; only ruminants, camelids and very large hindgut fermenters (rhinos, elephants) achieve this. Instead, many other herbivores (foregut fermenters such as kangaroos and small hindgut fermenters such as rabbits, voles and possums) have digestive systems that sacrifice maximal fibre digestibility for a capacity to process large amounts of forage, even when forage fibre content becomes very high. These different digestive strategies result in the wide range of nutritional niches found among mammals.