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铬是地壳中的微量元素之一，占地壳总量的0．02％。自1797年被法国化学家Louis Vanguelin首次发现并命名以来，住很长一段时剧内一直被认为是有毒的元素，甚至为致癌物质。这种误解一直持续到1959年，当时Schuarz提出一种假说认为，啤酒酵母中分离出来的铬是葡萄糖耐受因子(GTF)的活性组成部分。这之后，人们才对铬是有毒元素的看法开始改变。 相似文献
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自1797年法国化学家Luis Vaupuelin发现铬(chromium,Cr)元素以来,在很长的一段时间内,铬被认为是有毒有害的致癌物质.直到20世纪90年代以后,人们才逐步发现在动物饲料中添加有机铬(烟酸铬、酵母铬、吡啶羧酸铬、氨基酸螯合铬和蛋白质铬)对动物的生产性能有一定的促进作用.本文就有机铬的生化功能和营养作用及其应用进展作一综述. 相似文献
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1797年，法国化学家Louis Vauquelin首次在自然界发现铬（Cr）元素，很长一段时间内．铬一直被认为是有毒元素，甚至是致癌物质。1957年．Schwarz等实验证实，并提出啤酒酵母中含有葡萄糖耐量因子（GTF）假说。1959年，他们进一步证实GTF的重要活性组成部分是三价铬离子。尽管30年前已经确定了铬是动物营养的必需微量元素，但对畜禽营养方面的研究90年代初才开始。近年来的研究结果表明，铬对畜禽的生长．繁殖、免疫和胴体品质等均有影响。本文将从铬的理化特性．铬的代谢．铬的生物学功能以及铬对畜禽生长和生产性能影响等方面作如下综述． 相似文献
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饲料添加剂有机铬的研究进展和应用前景 总被引：6，自引：0，他引：6
在人和动物体内发现有70种元素，其中也包括铬，但铬在人和动物营养上有何意义，一直未被证实。1959年Merty和Schwary通过实验发现，在啤酒酵母中含有葡萄糖耐量因子glucosetolerancefac－tor（简称GTF），而GTF的重要活性组成部分是三价铬离子，铬才被人们普遍认为是人和动物不可缺少的微量元素。60年代后，人们开始在大鼠和人上进行铬的大量研究。结果表明，铬主要通过GTF协同和增强胰岛素的作用，进而影响糖、脂类、蛋白质和核酸代谢。而对畜禽铬营养特别是有机铬的营养作用和开发应用的研究自90年代初才开始。研究结果表明，具有生… 相似文献
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铬作为一种微量矿物元素,对提高猪生长性能,改善胴体品质,提高繁殖性能方面有重要作用,本文综述了铬制剂的生物活性、作用机理、吸收代谢及其在养猪生产中的应用研究现状,并展望未来铬营养的研究方向。很长时间以来铬（Cr）被认为是有毒有害元素,甚至是致癌物质。1954年,Curan发现大鼠肝脏合成胆固醇和脂肪酸的能力因铬而增加,并提出铬可能是动物必需矿物元素的假说。 相似文献
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有机铬对妊娠母猪繁殖性能的影响 总被引：4，自引：0，他引：4
18世纪 ,科学家最早发现铬的时候，一直认为铬是有毒元素，其后的研究才发现铬可能是动物必需的微量元素。铬对动物糖代谢、脂类代谢及蛋白质代谢等方面的研究已有不少的报道，铬的抗应激、增强免疫、改善猪的胴体品质和提高动物生产性能的功效也逐步被研究者所证实。目前关于有机铬的研究热点在繁殖猪群，繁殖效益是养猪生产中确定经济效益的主要因素，而合理的营养组成是实现母猪最大繁殖效益不可分割的重要部分；有机铬对母猪繁殖性能的影响，研究结果也不完全一致，在实际应用过程中，各猪场和饲料厂对有机铬的有效添加量和使用周期缺乏足够的认识，本试验旨在通过有机铬对妊娠母猪繁殖性能影响的研究，为生产应用提供科学的依据。 相似文献
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有机铬的研究进展及应用前景 总被引：1，自引：0，他引：1
在人和动物体内发现有70种元素,其中也包括铬,但铬在人和动物营养上有何意义,一直未被证实。自法国化学家N.L. Vauguelin1797年从红铅矿与盐酸反应的产物中提取出Cr2O3,并用木炭和铬酐共热得到金属铬粉以来,很长一段时间内,铬被认为是有毒有害元素,甚至是致癌物质。1955年Mertz和Schwarz实验证实,并提出啤酒酵母中含有葡萄糖耐量因子 相似文献
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微量元素硒（Se）于19世纪初被科学家发现，人们一直把它看成一种有毒物质，直到20世纪中叶，首次发现硒具有抗氧化功能，可防止犊牛和羔羊白肌病，其营养作用才开始引起重视，被认为是动物必需的矿物质元素。迄今为止，微量元素硒已在畜牧业生产中得到广泛应用。 相似文献
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铬在家禽中应用研究进展 总被引：1，自引：0，他引：1
铬是地壳中的微量元素之一 ,占地壳总量的0 0 2 %。对人和大鼠进行的大量研究表明 :铬主要通过加强胰岛素的功能来影响糖类、脂类、蛋白质及核酸的代谢。将铬作为动物营养素的研究始于 2 0世纪 6 0年代。但直到 90年代以后 ,人们才逐步发现在动物饲粮中加入铬对畜禽的生产性能有一定的促进作用。1 铬的营养机理1 1 铬与糖类代谢 家畜采食后机体内未被利用的葡萄糖通常以肝糖元的形式贮存于肝脏中 ,或转变为三酰甘油作为储备能量。这两种转化都需要胰岛素的作用才能完成 ,而葡萄糖耐受因子ＧＴＦ能增强胰岛素的功能 ,从而维持血液中正常… 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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乳酸杆菌作为益生菌广泛用于人和动物.本文综述了乳酸杆菌改善宿主健康的机制.乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道.文章重点讨论了乳酸杆菌表面成分(表面蛋白、脂磷壁酸和肽聚糖)与肠道受体(C型凝集素受体、Toll样受体和Nod样受体),阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制. 相似文献
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Billinghurst RC Brama PA van Weeren PR Knowlton MS McIlwraith CW 《American journal of veterinary research》2004,65(2):143-150
OBJECTIVE: To determine whether serum concentrations of biomarkers of skeletal metabolism can, in conjunction with radiographic evaluation, indicate severity of osteochondrosis in developing horses. ANIMALS: 43 Dutch Warmblood foals with varying severity of osteochondrosis. PROCEDURE: 24 foals were monitored for 5 months and 19 foals were monitored for 11 months. Monthly radiographs of femoropatellar-femorotibial and tibio-tarsal joints were graded for osteochondral abnormalities. Serial blood samples were assayed for 8 cartilage and bone biomarkers. At the end of the monitoring period, foals were examined for macroscopic osteochondrosis lesions. RESULTS: Temporal relationships were evident between certain serum biomarkers and osteochondrosis severity in foals during their first year. Biomarkers of collagen degradation (collagenase-generated neoepitopes of type-II collagen fragments, type-I and -II collagen fragments [COL2-3/4C(short)], and cross-linked telopeptide fragments of type-I collagen) and bone mineralization (osteocalcin) were positive indicators of osteochondrosis severity at 5 months of age. In foals with lesions at 11 months of age, osteochondrosis severity correlated negatively with COL2-3/4C(short) and osteocalcin and positively with C-propeptide of type-II procollagen (CPII), a collagen synthesis marker. Radiographic grading of osteochondrosis lesions significantly correlated with macroscopic osteochondrosis severity score at both ages and was strongest when combined with osteocalcin at 5 months and CPII at 11 months. CONCLUSIONS AND CLINICAL RELEVANCE: The ability of serum biomarkers to indicate osteochondrosis severity appears to depend on stage of disease and is strengthened with radiography. In older foals with more permanent lesions, osteochondrosis severity is significantly related to biomarker concentrations of decreased bone formation and increased cartilage synthesis. 相似文献