单宁酸对生长猪胃-小肠仿生消化中消化酶活性及饲粮粗蛋白消化率的影响

本试验旨在探讨单宁酸对生长猪胃、小肠仿生消化中消化酶活性及玉米-豆粕型饲粮干物质和粗蛋白消化率的影响,为评价单宁酸的生物学效应提供参考。试验一采用单因素完全随机设计,考察在无饲粮下2种单宁酸对猪模拟胃液、模拟小肠液消化酶活性的影响。设5个处理,单宁酸添加量分别为0 mg(胃液体积为20 mL,小肠液体积为22 mL);单宁酸1,10 mg;单宁酸1,20 mg;单宁酸2,10 mg;单宁酸2,20 mg。测定各处理的胃蛋白酶、淀粉酶、胰蛋白酶和糜蛋白酶的活性。试验二考察玉米-豆粕型饲粮添加单宁酸对猪仿生消化中胃、小肠阶段消化酶活性及养分消化率的影响。采用单因素完全随机设计,设5个处理,单宁酸在饲粮中的含量分别为0 mg·(2 g)^-1;单宁酸1,10 mg·(2 g)^-1;单宁酸1,20 mg·(2 g)^-1;单宁酸2,10 mg·(2 g)^-1;单宁酸2,20 mg·(2 g)^-1。测定仿生消化中胃阶段0.5和4 h时胃蛋白酶活性,小肠阶段0.5、4和8 h时淀粉酶、胰蛋白酶和糜蛋白酶活性及生长猪胃-小肠仿生消化测定饲粮的干物质和粗蛋白消化率。结果表明:1)无饲粮的情况下,和空白对照组相比,2种单宁酸对模拟胃液中胃蛋白酶活性无显著影响(P>0.05),单宁酸1比单宁酸2更高地降低了模拟小肠液中淀粉酶、胰蛋白酶和糜蛋白酶的活性(P<0.05)。2)在饲粮进行仿生消化的胃消化0.5~4 h内,除4 h时10 mg·(2 g)^-1添加量外,添加单宁酸1时胃蛋白酶的活性均显著高于添加单宁酸2时的相应值(P<0.05),除单宁酸2在消化0.5 h外,2种单宁酸在添加10 mg·(2 g)^-1时胃蛋白酶活性均显著高于20 mg·(2 g)^-1添加量的相应值(P<0.05)。在小肠仿生消化0.5 h时,饲粮中添加单宁酸1、2的2个水平对消化液中淀粉酶活性无显著影响(P>0.05),但均显著降低了糜蛋白酶的活性(P<0.05);单宁酸1的消化液中胰蛋白酶活性高于单宁酸2的相应值(P<0.05)。在小肠仿生消化4 h时,除添加水平为20 mg·(2 g)^-1时的糜蛋白酶活性外,饲粮中添加单宁酸1消化液中淀粉酶、糜蛋白酶活性高于添加单宁酸2的相应值,而胰蛋白酶活性低于添加单宁酸2的相应值(P<0.05)。单宁酸1、2的两个添加量均降低了胰蛋白酶和糜蛋白酶的活性(P<0.05)。在小肠仿生消化8 h时,饲粮中单宁酸的添加量影响了淀粉酶的活性,但单宁酸1和单宁酸2各两个添加量在淀粉酶的平均活性上无显著差异(P>0.05)。单宁酸1、2的两个添加量均降低了胰蛋白酶、糜蛋白酶的活性(P<0.05)。3)与对照组相比,两种单宁酸在两种添加水平下均显著降低了饲料粗蛋白消化率(P<0.05),且单宁酸2比单宁酸1更多地降低了饲粮粗蛋白的消化率(P<0.05)。综上所述,在有、无饲粮条件下,单宁酸对消化酶活性呈现不一致影响。单宁酸影响饲粮粗蛋白的消化率可能主要与消化液中糜蛋白酶活性降低以及单宁酸与饲粮中的化学成分形成螯合物降低了小肠消化酶的水解效率有关。

Effects of Tannic Acid on Digestive Enzyme Activity and Digestibility of Dietary Crude Protein in Simulated Gastric and Intestinal Digestion for Growing Pigs

This experiment was conducted to investigate the effects of tannic acid on digestive enzyme activity and digestibility of dry matter and crude protein of corn-soybean meal diet in the simulated gastric and small intestinal digestion for growing pigs, which will provide a reference for evaluating the biological effects of tannic acid. In the experiment 1, a single factor completely randomized arrangement was used to investigate the effects of 2 tannic acids without diet on digestive enzyme activities in simulated gastric and small intestinal fluid for pigs. Five treatments consisted of 0 mg tannic acid (the gastric fluid volume was 20 mL, the intestinal fluid volume was 22 mL);tannic acid 1,10 mg; tannic acid 1,20 mg; tannic acid 2,10 mg; tannic acid 2,20 mg. The activities of pepsin, amylase, trypsin and chymotrypsin were determined. The experiment 2 was to investigate the effects of tannic acid supplemention in corn-soybean meal diet on digestive enzyme activity in gastric and small intestinal simulated digestion phases and nutrient digestibility determined with the simulated digestion for growing pigs. Five treatments of dietary tannic acid concentration were 0 mg·(2 g)^-1; tannic acid 1, 10 mg·(2 g)^-1; tannic acid 1, 20 mg·(2 g)^-1; tannic acid 2, 10 mg·(2 g)^-1; tannic acid 2, 20 mg·(2 g)^-1, respectively. The activities of pepsin were measured at 0.5 and 4 h in the gastric digestion phase, and the activities of amylase, trypsin and chymotrypsin were measured at 0.5, 4, and 8 h in the small intestinal digestion phase. Simultaneously, the digestibility of dry matter and crude protein were determined for the diet. The results showed that:1) Without the diet, compared with the blank control group, the 2 tannic acids didn't significantly affect the activity of pepsin in the simulated gastric fluid(P>0.05); tannic acid 1 significantly reduced the activities of amylase, trypsin and chymotrypsin in the simulated intestinal fluid contrast to tannic acid 2 (P<0.05). 2) From 0.5 to 4 h of the simulated gastric digestion, except for the 10 mg·(2 g)^-1 supplementation level at 4 h, the activity of pepsin in simulated gastric fluid in the tannic acid 1 diet was significantly greater than that in the tannic acid 2 diet(P<0.05). Except for tannic acid 2 at 0.5 h, the pepsin activities in simulated gastric fluid in the 2 tannic acids added at 10 mg·(2 g)^-1 were significantly greater than that at 20 mg·(2 g)^-1(P<0.05). At 0.5 h of the simulated small intestinal digestion, except for the chymotrypsin activity at 20 mg·(2 g)^-1 supplementation level, the 2 levels of tannic acid 1 or 2 in the diet didn't significantly influence amylase activity in the digestive fluid(P>0.05), but both significantly reduced chymotrypsin activity(P<0.05). The trypsin activity of the digestive fluid in the tannic acid 1 was greater than that in the tannic acid 2(P<0.05). At 4 h of the simulated small intestinal digestion, except for the chymotrypsin activity at 20 mg·(2 g)^-1 supplementation level, the activities of amylase and chymotrypsin in digestive fluid was greater but the trypsin activity was lower in diet supplemented with tannic acid 1 than tannic acid 2(P<0.05). The supplement of tannic acids 1 and 2 reduced the activities of trypsin and chymotrypsin (P<0.05). At 8 h of the simulated small intestinal digestion, the concentration of tannic acid in diet affected the activity of amylase, but no significant difference was observed on the average activity of amylase between the treatments of tannic acid 1 and tannic acid 2(P>0.05). The supplement of tannic acids 1 and 2 reduced the activities of trypsin and chymotrypsin(P<0.05). 3) Campared with the control, the 2 tannic acids significantly reduced the digestibility of dietary crude protein at both levels (P<0.05). More reduction in digestibility of dietary crude protein was observed in tannic acid 2 than tannic acid 1 (P<0.05). In summary, inconsistent effect of tannic acid on digestive enzyme activities was presented in digestive fluid with or without diet, the tannic acid reduced the dietary crude protein digestibility maybe mainly related to the reduced activities of chymotrypsin in the digestive fluid and hydrolysis efficacy of digestive enzymes reduced by the formation of chelates between tannic acid and dietary components in the simulated digestion for growing pig.