Abstract: Reproduction period is one of the most important stages of life history in small mammals, during which the maternal energy requirements are maximized in lactation. To meet the energy requirements of their offspring, mothers usually increase energy intake to a ceiling, i. e. the maximal sustained energy intake (mSusEI). The notable plasticity of the digestive morphology and function is important for a variety of animals to cope with the changes in energy requirements. However, so far it is unclear if the mSusEI during peak lactation is constrained by the digestive system. In the present study, body mass, food intake, gross energy intake, digestibility, resting metabolic rate, and milk energy output, as well as the mass of gastrointestinal tracts and the digestive enzymes activity of the small intestine were examined in striped hamsters (Cricetulus barabensis) that were fed with high-fiber diet during lactation. The maternal energy intake and reproductive output were analyzed in the hamsters raising different litter sizes. The activity of digestive enzymes was also compared in the hamsters raising small, medium, and large litter sizes under the high-fiber diet feeding. The results showed that the energy budgets of the hamsters during lactation were correlated with litter size. The mSusEI was not significantly affected by high-fiber diet. The hamsters fed with high-fiber diet decreased digestive energy intake and digestibility significantly, but did not change their gross energy intake, compared to those fed with low-fiber control diet. The milk energy output was significantly decreased in the hamsters fed with high-fiber diet, which could not meet the energy requirements of offspring, resulting in decreased growth rate during the lactation period. The masses of stomach,small intestine, large intestine and caecum, as well as the activity of amylase, maltase and aminopeptidase of the small intestine were significantly higher in the hamsters fed with high-fiber diet than those fed with low-fiber control diet, while neither tract mass nor digestive enzyme activity was significantly affected by litter size. These data indicate that the mSusEI at peak lactation is constrained by the digestive system, providing support for the central limitation hypothesis. Based on the central limits to the mSusEI at peak lactation, the increases of fiber content in diet may decrease reproductive value.

Key words: Energy metabolism, High-fiber diet, Reproductive output, Litter size, Striped hamsters

摘要： 繁殖期是小型哺乳动物最重要的生活史阶段之一，哺乳期是母体能量需求最高的时期。为满足后代的能量需求，母体通常显著增加能量摄入，达到最大持续能量摄入(maximal sustained energy intake,mSusEI)。动物消化道形态和消化机能具有可塑性，然而消化系统是否限制了哺乳期mSusEI，尚不确定。本文以高纤维食物饲喂哺乳期黑线仓鼠(Cricetulus barabensis)，通过测定体重、摄食量、摄入能和消化率、代谢率、泌乳能量输出，以及消化系统重量和消化酶活性等，分析哺育不同胎仔数的母体能量摄入与繁殖输出，比较在不同能量需求的条件下，消化酶活性的变化。结果发现，黑线仓鼠哺乳期的能量收支与其哺育后代的数量有关，哺乳期mSusEI未受高纤维食物的显著影响。饲喂高纤维食物未影响摄入能，但显著降低了消化能和消化率，母乳能量输出也显著减少，不能满足后代幼体的能量需求，导致幼体发育变缓。高纤维食物使胃、小肠、大肠和盲肠重量显著增加，小肠淀粉酶、麦芽糖酶和氨基肽酶活性显著增强，但未受胎仔数的显著影响。结果表明，哺乳期mSusEI的瓶颈可能来自消化系统，支持中心限制假说。由于“中心限制”的存在，食物中纤维素含量升高可能会降低动物繁殖价值。

关键词: 能量代谢, 高纤维食物, 繁殖输出, 胎仔数, 黑线仓鼠