Afik D, Vidal E C, Martinez del Rio C, Karasov W H
Department of Wildlife Ecology, University of Wisconsin-Madison 53706, USA.
Am J Physiol. 1995 Aug;269(2 Pt 2):R413-20. doi: 10.1152/ajpregu.1995.269.2.R413.
Many birds exhibit seasonal switches in diet and thus alter the nutrients predominating their food intake. We tested for dietary modulation of small intestine (SI) enzymes in yellow-rumped warblers, a species for which such diet changes are well documented. Birds were fed three diets formulated from either fruit, insect, or seed. We predicted that SI carbohydrases and peptidases would be modulated in direct correlation with relative levels of dietary carbohydrate and protein, respectively. Aminopeptidase N activity was about twice as high in birds eating the highest protein content diet. In contrast, there was no significant dietary effect on any of the carbohydrase activities. There was a proximal-to-distal decrease in activities of all the carbohydrases but not aminopeptidase N. The carbohydrase levels of yellow-rumps are relatively low when compared with other species in the same family and most similar to lower levels found in primarily insectivorous birds rather than in primarily granivorous or nectarivorous species. Considering this and the fact that they do not exhibit dietary modulation of carbohydrase levels, we conclude that yellow-rumps are not highly adapted for handling dietary carbohydrates, especially starch, although they might still efficiently break down and absorb sucrose and maltose if retention time were sufficiently long.
许多鸟类在饮食上表现出季节性变化，从而改变了其食物摄入中占主导地位的营养成分。我们对黄腰林莺小肠（SI）酶的饮食调节进行了测试，黄腰林莺是一种饮食变化有充分记录的物种。给鸟类喂食由水果、昆虫或种子配制的三种饮食。我们预测，SI碳水化合物酶和肽酶将分别与饮食中碳水化合物和蛋白质的相对水平直接相关地受到调节。在食用蛋白质含量最高的饮食的鸟类中，氨肽酶N的活性大约是其他鸟类的两倍。相比之下，饮食对任何碳水化合物酶的活性都没有显著影响。所有碳水化合物酶的活性从近端到远端都有所下降，但氨肽酶N没有。与同科的其他物种相比，黄腰林莺的碳水化合物酶水平相对较低，并且与主要食虫鸟类中发现的较低水平最为相似，而不是与主要食谷或食蜜物种相似。考虑到这一点以及它们没有表现出碳水化合物酶水平的饮食调节这一事实，我们得出结论，黄腰林莺对处理饮食中的碳水化合物，尤其是淀粉，适应性不强，尽管如果保留时间足够长，它们可能仍然能够有效地分解和吸收蔗糖和麦芽糖。
