Grimsö Wildlife Research Station, S-770 31, Riddarhyttan, Sweden.
J Chem Ecol. 1991 Sep;17(9):1733-43. doi: 10.1007/BF00993725.
Mountain hares (Lepus timidus L.) commonly have high proportions of birch (Betula spp.) in their winter diets, whereas European hares (Lepus europaeus) do not. The effects of a birch extract added to laboratory diets offered to mountain hares and European hares on the digestibility and sodium balance were measured. The extract added contained total phenolics equivalent in amount to that occurring in diets containing 0, 40, 60 and 80% dry matter of birch twigs. Increasing dietary phenolic concentration led to reduced voluntary food intake and apparent protein digestibility in both hare species. No effects on apparent dry matter digestibility were observed. The highest concentration of birch extract caused severe sodium losses via the urine by European hares but not by mountain hares. The effects of the birch extract within the digestive system appear to be similar in the two hare species, whereas the mountain hare appears to be better adapted to the toxic effects that disrupted sodium balance in the European hare. These preliminary results suggest that detoxification rather than digestive abilityper se may contribute to different mammalian herbivores' feeding strategies.
高山野兔（Lepus timidus L.）在冬季的食物中通常含有较高比例的桦木（Betula spp.），而欧洲野兔（Lepus europaeus）则不然。本研究测量了向高山野兔和欧洲野兔提供的添加桦木提取物的实验室饮食对其消化率和钠平衡的影响。添加的提取物中总酚类物质的含量与含有 0、40、60 和 80%桦木嫩枝干物质的饮食中所含的酚类物质相当。饮食中酚类物质浓度的增加导致两种野兔的自愿食物摄入量和表观蛋白质消化率降低。然而，对表观干物质消化率没有影响。桦木提取物的最高浓度导致欧洲野兔通过尿液严重流失钠，但高山野兔则没有。桦木提取物在消化系统中的作用似乎在这两个野兔物种中相似，而高山野兔似乎更能适应扰乱欧洲野兔钠平衡的毒性作用。这些初步结果表明，解毒而不是消化能力本身可能有助于不同的哺乳动物食草动物的取食策略。
