牦牛与黑白花牛胃肠道内肽的吸收量及其对日粮蛋白质降解率的反应

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	牦牛与黑白花牛胃肠道内肽的吸收量及其对日粮蛋白质降解率的反应
	韩兴泰
学位类型	博士
导师	杜继曾
	1998
学位授予单位	中国科学院西北高原生物研究所
学位授予地点	中国科学院西北高原生物研究所
摘要	本文对牦牛、黑白花牛胃肠道内肽的吸收量、肽的主要吸收部位及肽吸收对日粮蛋白质、可降解蛋白质进食量的反应进行了研究。为全面阐述反刍动物对饲料蛋白质的利用情况，本文同时对NH_3吸收与尿素循环规律进行了研究。试验共分五个部分。试验１的目的是在门静脉和肠系膜动、静脉安装血导管，测定门脉血流量，为研究肽及其它营养物质的吸收提供试验动物和门脉血流量的基本信息。试验用体重不一的健康生长牦牛、泌乳牦牛和生长黑白花牛共13头，于绝食48 h后手术安装门静脉、肠系膜动、静脉导管，动物恢复正常采食3-4天后用对氨基马尿酸（PAH）作为标记物测定门脉血流量。观察表明，肠系膜导管的畅通时间在3-21之间（80%的管子在9天后被堵），门脉导管维持畅通的时间较长，13头安装有门脉导管的动物中仅一头其导管保持畅通一个月，其余12头牛其导管保持畅通四个月以上。在日粮精粗比为1:1、饲喂量略低于自由采食量的条件下，生长牦牛、泌乳牦牛及生长黑白花牛门脉的血流量分别为1.77（1.30～1.98）、2.26（1.66～2.56）和2.14（1.99～2.30）1/h.kgBW。血流量在同种动物个体之间、短期内同一个体不同次测定之间均呈较大差异。试验还发现，门脉血流量明显受采食的影响。分析表明，牦牛在单位体重、单位时间内的门脉血流量低于黑白花牛。由于肠系膜动脉导管大部分于术后十几日内被堵，后来的研究所用的动脉血样均取自颈动脉。试验2对颈动脉和肠系膜动脉中一些主要营养物质的浓度进行比较研究，为准确计算消化道内营养物质的净吸收提供必要的校正依据。试验用4头体重60-90kg的牦犊牛，3头体重150-200kg的成年泌乳母牦牛和4头体重190-200kg的生长黑白花牛，在维持饲喂水平下于晨饲前麻醉，行手术暴露肠系膜动脉和颈动脉后同时从两动脉采取血样，分析其中某些营养物质的含量。结果表明，无论是牦牛还是黑白花牛，其颈动脉和肠系膜动脉间被测营养物质浓度均有不同程度的差异。就母牛而言，肠系膜动脉中NH_3N、脲N及葡萄糖的含量均高于颈动脉，而游离氨基酸和肽氨基酸的含量低于颈动脉；就牦犊牛而言，肠系膜动脉中血糖、NH_3-N和肽氨基酸和肽氨基酸的含量低于颈动脉，而游离氨基酸和脲N的含量接近于颈动脉；就黑白花牛而言，肠系膜动脉中葡萄糖与脲N含量低于颈动脉，NH_3-N含量高于颈动脉。上述结果说明在测定这些营养物质的净吸收时不能将肠系膜动脉血样用颈动脉血样取而代之。试验3的目的是，1）通过测定NH_3-N、脲N和葡萄糖的净吸收，了解牦牛和黑白花牛在消化吸收方面可能存在的差异性，2）通过饲喂具有不同蛋白质降解率的日粮，观察可降解氮进食水平对NH_3-N吸收量和尿素循环量的影响。试验选用种内体重接近、装有门静脉导管和颈动脉导管的生长牦牛和黑白花牛各3头，在略低于自由采食水平下分别喂以六种不同的日粮，其中3种日粮，两种牛共用。各日粮其蛋白质和能量含量相近，但蛋白质在瘤胃内的降解率不同。经一定的预饲期后，从门静脉和颈动脉导管采取血样，颈动脉血样中NH_3N、脲N和葡萄糖的含量被校正成肠系膜动脉含量，由每日门脉血流量乘以动静脉营养物浓度差来计算每日NH_3-N、脲N和和葡萄糖的净吸收量。结果表明，随日粮蛋白质降解率升高，两促牛消化道内NH_3-N吸收量线性下降，葡萄糖的净吸收量线性增加。随日粮精饲料干物质降解率升高，经瘤胃壁循环进入瘤胃的尿素量增加，被吸收NH_3-N的利用率提高。进一步分析发现，尿素的循环量只与饲料非结构性碳水化合物的发酵水平有关，而与日粮蛋白质降解率和代谢能含量无关。这些结果说明，给反刍动物饲喂具有高蛋白质降解率和含较高非结构性碳水化合物的日粮将有助于提高动物对饲料蛋白质的利用率。从动物品种看，牦牛对被吸收NH_3-N的利用率显著低于黑白花牛，而且前者对葡萄糖的吸收几乎为零，后者对葡萄糖的负吸收值很大，说明前者对饲料氮的利用率较低，后者用于肠道代谢的葡萄糖量较高。试验4的目的是，1）研究同等蛋白质进食水平下降解蛋白质进食量对肽吸收的影响，2）研究同等可降解蛋白质进食水平下蛋白质进食量对肽吸收水平的影响，3）探讨牦牛和黑白花牛胃肠道被在肽吸收方面可能存在的种间差异。选用种内体重接近、装有门静脉、颈动脉导管的生长牦牛和生长黑白花牛各3头，在略低于自由采食水平下分别喂以3种不同的日粮。3 种日粮中每两种日粮组成一对比试验，在相同的采食水平下，它们或有相同的总蛋白质进食量、不同的降解蛋白质进食量，或有相同的可降解蛋白质进食量，不同的总蛋白质进食量。各日粮代谢能含量相同。经一定的预饲期后，从门静脉和颈动脉采样制取血浆，血浆去蛋白质后用氨基酸自动分析仪分析其中的游离氨基酸和水解氨基酸含量，水解前后氨基酸含量之差被视为肽结合氨基酸。颈动脉含量被校正为肠系膜动脉含量。由门脉血流量乘以动静脉浓度差来计算游离氨基酸和肽氨基酸的净吸收量。试验结果表明，肽与氨基酸的吸收水平与可降解蛋白质的进食量有关，而与总蛋白质的进食量无关。随可降解蛋白质进食量升高，吸收进入血液的肽氨基酸的数量箕高，游离氨基酸的数量下降。在略低于自由采食水平下，吸收进入牦牛和黑白花牛门脉的肽氨基酸分别占被吸收总氨基酸的85%～99%和91%～94%，游离氨基酸的数量分别只占1%～15%和6%～9%。这些结果证明反刍动物消化道对蛋白质的吸收以肽的形式为主，以氨基酸形式为辅。在被吸收的肽氨基酸中，谷氨基酸的数量显著高于其它氨基酸，表明被吸收的小肽主要由谷氨酸组成。从动物品种来年看，黑白花牛对游离必需氨基酸的吸收大于对游离非必需氨基酸的吸收，牦牛则相反，甚至不吸收游离必需氨基酸。试验5的目的是，在试验4的基础上进一步一量研究由肠系膜吸收系统和非肠系膜吸收系统吸收进入牦牛门脉的游离氨基酸和肽氨基酸的数量。试验用3头平均体重172.3±18.6kg、处于泌乳后期的成年母牦牛，手术安装门静脉、肠系膜动、静脉导管，其中肠系膜静脉导管安装两个，一个其顶端位于肠系膜静脉弓，另一个其顶端位于肠系膜总静脉中，前者用标记物连续灌注，后者用于采取血液样品。用PAH作为标记物测定门静脉和肠系膜静脉血流量。动物手术前后均按维持水平饲喂，术后第7-8天分别从门静脉、肠系膜静脉和肠系膜动脉导管中采取血样制备血浆，用氨基酸自动分析仪分析其中游离和水解后氨基酸含量，肽氨基酸被视为水解前后氨基酸含量之差。
其他摘要	The present study was conducted to determine the net absorption of ammonia nitrogen, urea nitrogen, glucose, free and peptide amino acids in portal-and mesenteric-drained yak and Holstein steers fed diets containing different level of ruminal protein degradability. Net peptide amino acids fluxes across mesenteric and non-mesenteric absorptive systems were also measured. The study was composed of five experiments. The objectives of experiment 1 was to implant catheters into portal vein, mesenteric vein and mesenteric artery with correct locations and to measure the portal blood flow to provide experimental animals and information regarding portal blood flows for the experiments conducted later in this study. Seven yak calves, three lactating yaks and three Holstein steers were used, a detailed method was described for implanting and maintaining catheters in portal vein, mesenteric vein and mesenteric artery, portal blood flows were measured by continuous para-aminophippurate (PAH) infusion. Catheters implanted in the mesenteric vessels remained patent for 3-21 days, the portal catheters in 12 animals remained functional until the animals were killed after a four-month experiment period for commercial purpose. The average portal blood flow rates of yak calves, lactating yaks and Holstein steers fed near ad libitum experimental diets were 1.77 (1.30-1.98), 2.26 (1.66-2.56) and 2.14 (1.99-2.30) 1/h. kg BW, the value of yaks was lower than that of Holstein steers. Data indicated that the portal blood flow greatly varied with individual, with determination in short time, and with time respect to feeding. Because most of the mesenteric catheters remained patent for only several days, blood samples had to be taken from carotid artery in later experiments. Experiment 2, therefore, was carried out to determine whether differences exist in the concentrations of nutrients between carotid and mesenteric arteries. Four yak calves, three lactating yaks and four Holstein steers fed experimental diet at maintenance level before surgery were used, blood samples were taken from carotid and mesenteric arteries under anaesthetized condition and deproteinized. Concentrations of ammonia-nitrogen, urea-nitrogen, glucose, free and peptide amino acids were analyzed. Data indicated there were significant differences in metabolite concentrations between carotid and mesenteric artery. For lactating yaks, ammonia nitrogen, urea nitrogen and glucose were higher, and free and peptide amino acids were lower in mesenteric artery than in carotid artery; for yak calves, glucose, ammonia nitrogen and peptide amino acids were lower in mesenteric artery than in carotid artery, free amino acids and urea nitrogen were similar in the two arteries; for Holstein steers, glucose and urea nitrogen were lower and ammonia nitrogen was higher in mesenteric artery than in carotid artery. These results suggest that the mesenteric arterial blood could not be replaced by carotid arterial blood when net absorption of the above metabolites is studied. The objectives of Experiment 3 was 1) to measure the net absorption of ammonia nitrogen, urea nitrogen, and glucose in yaks and Holstein steers and to determine the possible differences in nitrogen digestion and metabolism between the two species, and 2) to evaluate the effect of degradation level of dietary crude protein in the rumen on ammonia, urea and glucose absorption. Three growing yaks and three Holstein steers fitted with catheters in the portal vein and carotid artery were fed ad libitum 6 diets having different ruminal protein degradability and similar crude protein and metabolizable energy contents. Blood samples were taken from portal vein and carotid artery, plasma metabolites were analyzed. Net absorption was calculated as difference in portal-arterial concentration time portal blood flow. Ammonia absorption decreased and glucose absorption increased as dietary protein degradability increased. Increasing ruminal dry matter degradation increased negative urea-nitrogen absorption and increased the utilization of absorbed ammonia nitrogen. Dietary starch level seemed to be the main determinant of urea absorption, decreasing dietary starch or non-structural carbohydrate level decreased urea net transfer to the rumen. It seemed there was no relationship between dietary protein degradability and net urea transfer. The utilization of absorbed ammonia nitrogen (expressed as urea nitrogen transfer to the rumen / absorbed ammonia nitrogen) and the negative glucose absorption were higher in Holstein steers than in yaks. Experiment 4 was conducted 1) to study the effects of total protein intake and degradable protein intake on amino acids and peptide absorption, and 2) to ascertain the possible differences in peptide absorption between the two species. Fluxes of peptide and free amino acids across the gastrointestinal tract of four yaks and four Holstein steers fitted with catheters were quantified. Animal were fed three isocaloric diets at 12-h intervals to form two comporative trials: one had equal total protein intake and different degradable protein intake, the other had equal degradable protein intake and different total protein intake. Blood was obtained from the portal vein and carotid artery, the plasma was deproteinized and analyzed for free amino acids. An aliquot of deproteinized plasma was hydrolyzed in HCI and analyzed for total amino acids. Peptide amino acids were calculated as the differences between total and free amino acids. The flux of free and peptide amino acids across the portal-drained viscera were calculated as the product of venoarterial differences time blood flow. Both free and peptide amino acids were affected by degradable protein intake and not affected by total protein intake. Increasing degradable protein intake increased peptide amino acids absorption and decreased free amino acids absorption. For yaks, the peptide amino acids accounted for 85%-99% of the total amino acids absorbed into the portal vein, and for Holstein steers, the value was 91%-94%. The flux of free amino acids across the gastrointestinal was minimal. This results suggests that in ruminants, the dietary protein is mainly absorbed in the form of peptide instead of amino acid. There was no difference in peptide absorption between the two species. However, the flux of essential free amino acids across the portal vein was higher in Holstein steers than in yaks. In order to ascertain the site of peptide absorption, Experiment 5 was conducted and the flux of both free and peptide amino acids across the mesenteric and non-mesenteric portions was quantified. Three lactating yaks, weighing 172.3 kg and having sampling catheters implanted in the mesenteric artery, portal vein, and mesenteric vein prior to its convergence with the splenic vein were fed a concentrate/straw diet at maintenance level. Mesenteric and portal blood flow were determined by measuring the dilution of PAH that was infused constantly into a distal mesenteric vein. Non-mesenteric blood flow was calculated as the difference between portal and mesenteric blood flow. Blood plasma was obtained from blood collected from the portal vein, mesenteric vein and mesenteric artery. The plasma was deproteinized and analyzed for free amino acids. An aliquot of deproteinized plasma was hydrolyzed in HCI and analyzed for total amino acids. Peptide amino acids were calculated as the differences between total and free amino acids. The flux of free and peptide amino acids across mesenteric and non-mesenteric-drained viscera were calculated as the product of venoarterial differences time blood flow. The flux of peptide amino acids appeared in the portal vein accounted for 92% of the total amino acids. Of the peptide amino acids absorbed into portal vein, 78% came from non-mesenteric system and 22% came from mesenteric system. This result suggests that the non-mesenteric system is the main site of peptide absorption. Of the free amino acids absorbed into blood, 58% came from mesenteric system and the remaining 42% came from non-mesenteric system. This result suggests that the non-mesenteric system has the ability to absorb amino acids.
页数	77
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3022
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	韩兴泰. 牦牛与黑白花牛胃肠道内肽的吸收量及其对日粮蛋白质降解率的反应[D]. 中国科学院西北高原生物研究所. 中国科学院西北高原生物研究所,1998.

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