【作者】 向枭；

【导师】 叶元土；

【作者基本信息】 西南农业大学 ， 生物化学与分子生物学， 2002， 硕士

【摘要】 酶是催化生物化学反应的一类特殊的蛋白质，在生物体内有独特和关键的作用。鱼类消化道内分布的各种消化酶主要是对所摄取的物质进行消化，分解为可被吸收的小分子物质而进行利用。鱼类消化酶的活性与其食性、食物组成、环境条件、个体的发育阶段等因素有关。同时同种鱼类消化道的不同部位的消化酶活性也各不相同。对各种饲料物质的消化利用程度也有差异。鲇(Silurus asotus Linnaeus)为鲇形目鲇科中的一种生长较快，个体较小的经济鱼类，是广泛分布于长江干流及其支流、嘉陵江等中的一种经济鱼类。其肉质鲜美，具有较高的食用价值。对于鲇消化生理的研究还未见报道。 酶的活性及对饲料的消化率和酶解能力是评定鱼类对营养物质利用能力的重要指标。叶元元土等(2000)对草鱼的离体酶解动力学的研究和王友慧等(2002)对大眼鳜和斑点叉尾鮰的离体酶解动力学的研究表明，不同食性的鱼类对同种饲料的酶解能力不同：同种鱼类不同部位的酶解能力和消化能力也各不相同。本研究围绕鲇消化道的结构、主要消化酶的活性及其对常用饲料原料的离体消化和酶解动力学，进行了如下三个试验。其目的是为了研究鲇的消化生理，丰富和完善鲇的生物学资料。建立一种快速、准确评价饲料营养价值的研究方法。 试验一：鲇消化消化道结构与食物的适应性研究 以嘉陵江北碚段体长14.2～35.2cm，体重22.0～366.5g的鲇为试验对象，测定其消化道各部位的pH值和比肠长、比肠重、比胃重、比肝胰脏重、比内脏重等消化道指数。探讨鲇的消化道结构与食性的关系。结果如下： 1、鲇消化道从胃到后肠的消化液pH值变化较大。从胃液中的4.8—6.2到后肠中的6.5～7.0，胃液的酸性较强，不但有利于对食物的酸化，而且有利于胃蛋白酶作用的发挥。 2、鲇的比肠长为0.726±0.061， 比胃重为0.027±0.006，比胰脏重为0.022±0.0029，低于杂食性鱼类和草食性鱼类，且随着鱼体的生长，其比胃重、比肠重、比肝胰脏重和比内脏则相对降低。 试验二：鲇胃肠道和胰脏蛋白酶、淀粉酶活性的研究 以嘉陵江北碚段中的体重92.5～125.5g，平均体重105.36±12.81g，体长18.64～23.81cm，平均体长21.57±4.63cm的鲇为试验对象，分别测定胃肠道和胰脏中蛋白酶、淀粉酶最适温度、最适pH值及消化道各部位蛋白酶和淀粉酶的活性。目的为了探讨鲇的消化能力。结果如下： 站消化沮主要消化道活性及对饲料蛋白质酶解动力学研究 卜贴胃、前肠、中肠、后肠和胰液中蛋白酶的活分别为152．27土3．53、254．55上2．74、75．55土2．69、64．59土3．16和 179．08fi．97ug／g．min，淀粉酶的活性分另为242．05土4．24、196．67土1．59、166．41土1．06、151．28土2．25和 1013．58土4．83mg／g．hr。J＿l差异显著（P（．05）。 2．贴胃、肠道、胰脏中蛋白酶最适温度分别为400C、44OC、36OC；淀粉酶的最适拙L度分别为44℃、40℃、40℃。 3、贴胃、肠道及胰脏的蛋白酶活力的最适PH值分别为2．2、7．0和7．4；淀粉酶的活力的最适PH值分别为 7．0、7．4和 7．0。 试验三、站胃肠道和胰脏对饲料酶解能力的研究 以嘉陵江北硷段中的体重92．5叶．sg，平均体重105．36土12．slg，体长18石4～23．slcm，平均体长ZI．57土4．63cm的站为试验对象。在离体条件下测定了其消化道各部位的粗酶液对7种饲料原料干物质和粗蛋白的离体消化率和对饲料蛋白质的酶解动力学。目的为了探讨贴对饲料的消化能力，寻求一种简便／快速地评价饲料营养价值的方法。结果表明： 1、贴对鱼粉、豆粕、菜粕、棉粕、肉粉、酵母粉、啤酒蛋白粉等七种饲料原料的干物质的总消化率③胃、肠、肝胰脏对各原料的干物质总消化率）为：鱼粉为 49．15“豆粕为44．98％、菜粕为41．44％、棉粕为47．37％、肉粉为46．68％、酵母为35．32％、啤酒蛋白粉为31．73为对粗蛋白的总消化率怕胃、肠、肝胰脏对饲料粗蛋白质的总消化率）为鱼粉49．93％、豆粕48．15％、菜粕39．44％、棉粕28．34％、肉粉为34．50％、酵母为24．16％、啤酒蛋白粉为 20．94％，差异显著（P＜0．05）。 2、鱼粉、豆粕、菜粕、棉粕、肉粉、酵母粉、啤酒蛋白粉等七种饲料原料在站消化道粗酶液的酶解中氨基酸生成的总速度分别为：鱼粉16．45ling几r、豆粕14．756mg儿r、菜粕14．114mg／hr、棉粕11．836mg／hr、肉粉13．177ms／hr、酵母11．429 mg／hr、啤酒蛋白粉10．674mg／hr，差异显著（P＜0．05）。 根据上述试验结果，综合分析表明： l、站的消化能力与其消化道结构和食性相适应。其消化道指数与肉食性鱼类相一致。对饲料中蛋白质有较强的消化能力。 2、站消化道各部分主要消化酶的活性强度不同。贴蛋白酶活性为前肠＞胰脏）胃＞中肠＞后肠；而淀粉酶的活力大小则以胰脏〕骨前肠中肠＞后肠。胰脏的蛋白酶的活力仅次于前肠，高于胃、中肠和后肠；胰淀粉酶的活力则显著地高于其它组织u刃．05人 说明贴消化道前段对饲料的消化起主要作用。2更多还原

【Abstract】 Three experiments were conducted to study protease and amylase in stomach,intestine and hepatopancreas of Silurus asotus linnaeus. The results are followed:Experiment one: The experiments were conducted to study the pH value and the digestive tube index in stomach,intestine,hepatopancreas of Silurus asotus linnaeus, The results are followed:1. The pH value in digestive tube of Silurus asotus linnaeus is changed from stomach to post intestine.The pH value of stomach is 4.8-6.2,and that of post intestine is 6.5-7.0.the acidity of stomach is very strong . Not only it can acidulate the feeds,but also can be benefit to the effect of protease in stomach.2. The value of intestine length / body length of Silurus asotus linnaeus is 0.726+ 0.061,the stomach weight / body weight and hepatopancreas weight / body weight are 0.027 ± 0.006,0.022 ± 0.0029 respectively.it is smaller than that of herbivorous fishes and omnivorous fishes. The ratio of stomach,intestine, hepatopancreas and viscera weight to body weght of Silurus asotus linnaeus are deduce with growing.Experiment two:With Silurus asotus linnaeus, The activity , optimum pH and optimum temperature of protease and amylase in shomach,intestine and hepatopancreas were measured. The results are followed:1. The protease activities of stomach, antio intestine,middle intestine,post intestine and hepatopancreas are 152.27±3.53,254.55±2.74 ug/g.mm,75.55±2.69 ug/g.min,64.59±3.16 ug/g.min and 179.08 ±1.97ug/g.min in Silurus asotus linnaeus respectively .The amylase activities are 242.05±4.24 mg/g.h, 196.67±1.59 mg/g.h, 166.41 ± 1.06 mg/g.h, 151.28±2.25 mg/g.h and 1013.58 ± 4.83mg/g.h respectively.the difference was significent (P<0.05) .2. The optimum temperature value of stomach, intestine and hepatopancreas for protease are40℃, 44℃ and 36℃ respectively ,and for amylase are 44℃,40℃ and40℃ respectively in Silurus asotus linnaeus.3. The optimun pH value of shomach, intestine and hepatopancreas for protease are 2.2,7.0 and 7.4 respectively,and for amylase are 7.0,7.4 and 7.0 respectively in Silurus asotus linnaeus,Experiment three: The experiments were conducted to study enzymolysis kinetics and digestive rate in vitro of Silurus asotus linnaeus to fish meal,soybean meal,rapeseed meal, cottonseed meal, meat meal, brewers dried yeast and beer gluten meal.The enzyme is crude enzyme that was obtained from stomach, intestine and hepatopancreas in the fish. The digestive ability was determined:1. The digestive rate of fish meal,soybean meal,rapeseed meal, cottonseed meal, meat meal, brewers dried yeast and beer gluten meal to the dry matter are 49.15%, 44.98%, 41.44%, 47.37%, 46.68%, 35.32% and 31.73% respectively;those of the crude protein digestibility are 49.93%, 48.15%, 39.44%, 28.34%, 34.50%, 24.16% and 20.94% respectively(P<0.05).2. The rates of amino acid were producted from the enzymolysis fluid of fish meal,soy bean meal,rapeseed meal, cottonseed meal, meat meal, brewers dried yeast and beer gluten meal are 16.45Img/h, 14.756mg/h, 14.114mg/h, 11.836mg/h, 13.177mg/h, 11.429 mg/h, 10.674mg/h respectively (P<0.05 ).The result indicated that:1. The digestive ability is adapt to feeding and construction of digestive tube.the digestive tube index are consistent the other garnivoroue fishes.the digestive ability to protein in feeding is very strong.2. The activities of protease and amylase in different part of gut were different.the activity of protease in antio intestine is the hightest,that of hepatopanceas is the second, that of middle intestine and post intestine are low; the activity of amylase in hepatopanceas is the hightest,that of stomach is the second,that of middle intestine and post intestine are low within 0-4 hours. The protease activity in the hepatopancreas is the hightest,and that in the post intestine is lowest.the amylase in the hepatopancreas is higher than that in the intestine and stomach(P<0.05).The front digestive tube of Silurus asotus linn更多还原