中文摘要：

胃肠道是一个复杂的消化系统,每一部分都具有独特的生理特征.酸碱度（pH）是消化道重要的生理指标之一,其对营养物质的消化、吸收和肠道微生物的生长等具有重要影响.为了研究草鱼在食物消化过程中,肠道的酸碱度变化,测定了草鱼肠道食物糜、肠液和黏膜的pH.结果显示,随着食物的消化,它们的pH都有下降的趋势.肠道食物糜pH在6.86±0.24到8.43±0.10之间,肠液pH在7.14±0.22到8.63±0.02之间,相同时间点相同肠段两者之间的pH差异很小,并且在实验期间两者的pH变化趋势相同.黏膜pH在6.23±0.04到6.7±0.13之间,为弱酸性.除了时间点12h外,相同时间点和相同肠道部位黏膜的pH与食物糜、肠液的pH相比均有显著性差异（P〈0.05）.分析发现草鱼摄食食物的pH与上述三相的pH之间均有显著性差异（P〈0.05）,研究结果为草鱼消化生理及营养学研究提供了基础资料.

英文摘要：

The gastrointestinal tract is a complex digestive system, and each section has its unique physiological characteristics. Hydrogen ion concentration （pH） is an important physiological indicator of the digestive tract. It involves theprocess of digestion and absorption of nutrients and the growth of intestinal microbes. This study investigated thechange of pH level of the intestinal tract in grass carp （Ctenopharyngodon idellus） during food digestion period. The pHlevels of intestinal chyme, fluid and mucosa of the fish were measured at different time points after food ingestion. Theresults indicated food digestion resulted in significant decreases in pH of the intestinal tract. The pH levels of the intestinal chyme and fluid ranged from 6.86±0.24 to 8.43±0.10 and from 7.14±0.22 to 8.63±0.02, respectively. Within eachintestinal segment, there was no significant difference in pH between the intestinal chyme and fluid at each time point.By contrast, the pH levels of intestinal mucosa were between 6.23±0.04 and 6.7±0.13, significantly lower than measurements made in the intestinal chyme and fluid （P〈0.05）, with the exception of the 12h postingestion. Further analyses found that the pH level of the fish diet was significantly different with the pH levels of intestinal chyme, fluid andmucosa （P〈0.05）. The present study advances the understanding of the digestive physiology in grass carp.