DIGESTA RETENTION AND DIGESTIVE PERFORMANCE IN SCIURID AND MICROTINE RODENTS - EFFECTS OF HINDGUT MORPHOLOGY AND BODY-SIZE
DIGESTA RETENTION AND DIGESTIVE PERFORMANCE IN SCIURID AND MICROTINE RODENTS - EFFECTS OF HINDGUT MORPHOLOGY AND BODY-SIZE
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DOI：
10.1086/physzool.66.3.30163700
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发表时间：
1993-05-01
期刊：
影响因子：
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通讯作者：
KENAGY, GJ
中科院分区：
文献类型：
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作者：
HUME, ID;MORGAN, KR;KENAGY, GJ
为了研究后肠形态和体型对啮齿动物消化性能的影响，我们将三种不同纤维含量（7%、22%和28%）的饲料喂给三种动物：黄松花栗鼠（Eutamias amoenus） （55-60 g体重）、哥伦比亚地松鼠（600-700 g体重）、土拨鼠（2000 - 3000 g体重）和Townsend田鼠（55-60 g体重）。除了花栗鼠在高纤维饮食中体重下降外，所有物种在这三种饮食中都能保持体重。我们测量了三种饮食的摄入量和消化率，并比较了7%纤维饮食中液体消化物（标记为Co-EDTA）和大颗粒（标记为cr - mormorted植物细胞壁）的通过率。对田鼠来说，液体的平均滞留时间（MRT +/- SE） （14.8 +/- 1.9 h）大于大颗粒（13.1 +/- 2.4 h） （P = 0.02，配对t检验）。这表明近端结肠消化阶段的分离和液体消化的选择性保留，可能在盲肠，这意味着小的，高度可消化的食物颗粒和细菌被优先保留在盲肠，这导致该系统更有效的消化。相比之下，在三种sciurids中，流体的mrt与大颗粒相同或更小，表明没有选择性液体潴留。在所有物种中，MRTs随体型的增加而增加。在所有三种饮食中，田鼠的干物质消化率都高于花栗鼠，旱獭的干物质消化率也高于低纤维饮食中的田鼠。我们的研究结果证实了一个普遍的预测，即田鼠可以比花栗鼠利用更多的纤维食物，因为它们在更复杂的近端结肠中分离食糜，并在更大的盲肠中选择性地保留液体。在Sciuridae中，越来越大的体型（以及相对于代谢率的更大的绝对肠道容量）抵消了Sciuridae相对简单的后肠的缺点。
To examine the effects of hindgut morphology and body size on the digestive performance of rodents, we fed diets of three different fiber contents (7%, 22%, and 28%) to three species of sciurids-yellow-pine chipmunks (Eutamias amoenus) (55-60 g body mass), Columbian ground squirrels (Spermophilus columbianus) (600-700 g), and hoary marmots (Marmota caligata) (2,000-3,000 g)-and to Townsend voles (Microtus townsendii) (55-60 g), a microtine rodent. All species generally maintained body mass on all three diets, except that chipmunks lost mass on the high-fiber diet. We measured intake and digestibility of the three diets and compared rates of passage of fluid digesta (marked with Co-EDTA) and large particles (marked with Cr-mordanted plant cell walls) on the 7% fiber diet. For voles, the mean retention time (MRT +/- SE) of fluid (14.8 +/- 1.9 h) was greater (P = 0.02, paired t-test) than that of large particles (13.1 +/- 2.4 h). This indicates separation of digesta phases in the proximal colon and selective retention of fluid digesta, probably in the cecum, which means that small, highly digestible food particles as well as bacteria are preferentially held in the cecum, which results in a more effective digestion by this system. In contrast, in the three sciurids, MRTs of fluid were the same or less than those of large particles, indicating no selective fluid retention. Among all species, MRTs increased with increasing body size. Dry matter digestibility was greater in the voles than in the chipmunks for all three diets and was greater in marmots than in voles for the low-fiber diet. Our results confirm the general prediction that voles can utilize more fibrous foods than chipmunks because of separation of digesta in a more complex proximal colon and selective retention of fluid in a larger cecum. Within the Sciuridae, increasingly larger body size (and bence a larger absolute gut capacity relative to metabolic rate) offsets the disadvantage of the relatively simple sciurid hindgut.