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传统营养学的观点认为，蛋白质只有水解成氨基酸后才能被动物利用，但随后的研究发现，小肽能被动物机体整体吸收、利用，因而，小肽成为人们研究的热点。本文对小肽的营养，小肽在反刍动物中的吸收途径、机制，反刍动物对小肽的利用以及小肽对奶牛生产性能的影响进行了综述。 相似文献
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传统的经典蛋白质营养理论即氨基酸营养理论认为,动物采食的日粮蛋白质在消化道内经蛋白酶和肽酶作用降解为小肽和游离氨基酸,游离氨基酸可被动物直接利用,而小肽只有进一步降解为游离氨基酸才能被利用。但在后来的一些研究中发现,用纯合日粮或低蛋白质平衡氨基酸日粮饲喂动物,并不能达到最佳生产性能。Agao等(1953)首先观察到肠道能完整地吸收转运双甘肽。Neway等(1960)的研究为小肽能被完整吸收提供了证据。Hara等(1984)在小肠黏膜上发现了小肽载体。Garder(1984)研究也表明,大量小肽能直接被吸收,进入体循环。Webba(1989)研究表明,蛋白… 相似文献
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随着人们对蛋白质消化吸收及代谢规律研究的深入，蛋白质消化吸收理论不断得到完善。早在1865年，Kollinker和Muller就提出，蛋白质在肠道的消化最终成为游离氨基酸。现在营养学氨基酸平衡理论，便是以这个假设为基础的。而关于小肽可能被直接吸收的假设，早在100多年前就被提及，但一直因缺乏直接证据而受到忽视。直到Newey和smvth首先提出了令人信服的小肽可被完整吸收的论据，小肽的营养和吸收才逐渐被人们所重视。在近几十年的研究中，人们发现，蛋白质在动物消化道中消化酶作用下的水解产物大部分为2或3个氨基酸残基的小肽，它们是以完整形式被吸收并进人循环系统而被组织利用的。动物营养学家也发现，动物对饲料中各种氨基酸的利用程度并不完全受单一限制性氨基酸的影响，当动物采食按理想氨基酸模式配制的纯合日粮或低蛋白氨基酸平衡的日粮时，动物并不能获得最佳生产性能，因此，一些学者提出，动物要获得最佳的生产性能，日粮中必须有一定数量的完整蛋白质和小肽的观点。基于以上2个发现，人们提出了小肽的营养学说。 相似文献
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随着人们对蛋白质消化吸收及其代谢规律研究的深入，蛋白质消化吸收理论不断得到完善。早在1865年，Kollinker和Muller就提出蛋白质在肠道的消化最终成为游离氨基酸。现在营养学氨基酸平衡理论，便是以这个假设为基础的。而关于小肽可能被直接吸收的假设，早在100多年前就被提及，但一直因缺乏直接证据而受到忽视。直到Newey和Smyth首先提出了令人信服的小肽可以被完整吸收的论据，小肽的营养和吸收才逐渐被人们所重视。在近几十年的研究中，人们发现蛋白质在动物消化道中消化酶作用下的水解产物大部分为2或3个氨基酸残基的小肽，它们是以完整形式被吸收并进入循环系统而被组织利用的。动物营养学家也发现，动物对饲料中各种氨基酸的利用程度并不完全受单一限制性氨基酸的影响，当动物采食按理想氨基酸模式配制的纯合日粮或低蛋白氨基酸平衡的日粮时，动物并不能获得最佳生产性能，因此，一些学者提出动物要获得最佳生产性能，日粮中必须有一定数量的完整蛋白质和小肽的观点。基于以上2个发现，人们提出了小肽的营养学说。 相似文献
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传统的蛋白质营养理论认为,蛋白质在肠道中都被消化成氨基酸,然后通过肠壁被机体吸收,蛋白质营养就成了氨基酸营养。事实上,许多试验表明,用纯化组合日粮或低蛋白质平衡氨基酸日粮饲喂动物,并不能使其表现出最佳生产性能。随着研究的深入开展,产生了一些蛋白质营养的新认识和新观点,其中最为重要的应是小肽营养的理论,已逐渐被接受,蛋白质营养包括氨基酸营养和小肽营养。当蛋白质以小肽形式供给时,可提高动物对蛋白质的利用率,进一步发挥动物的生产潜能,具有增强动物免疫、防病抗病能力、改善动物产品品质等重要作用。对于反刍动物的蛋白质… 相似文献
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小肽的吸收机制与营养研究进展 总被引：1，自引：0，他引：1
近些年来的试验研究证明,小肽是蛋白质的主要消化产物,在氨基酸的消化、吸收和代谢中起着非常重要的作用。文章就小肽在单胃动物和反刍动物的吸收机制、小肽的营养作用和影响小肽吸收的因素以及小肽在蛋白质代谢中的作用分别加以综述。 相似文献
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魏静 《四川畜牧兽医学院学报》2009,(4):28-32
在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。 相似文献
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本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。 相似文献
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REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air. 相似文献
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Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF
Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo. 相似文献
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以国际标准强毒Ｒ株人工感染非免疫产蛋鸡,定时扑杀,分别从鼻窦、眶下孔、气管、肺、气囊、卵巢和输卵管分离ＭＧ,并收集感染鸡所产蛋分离ＭＧ。结果表明,人工感染４８小时后上、下呼吸道及肺已被全面感染,９６小时气囊已被感染,１２０小时输卵管已能分离到ＭＧ,卵巢始终分离不到ＭＧ。人工感染鸡自１４４小时便能在其所产蛋中分离出ＭＧ。药物治疗能在７２小时内消除感染,油乳剂苗则需２４天后逐渐降低蛋内ＭＧ分离率,药物卵内注射、种蛋药浴、高温处理均能杀死卵内ＭＧ,但以研制的种蛋浸泡剂药浴效果为最好。 相似文献