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一、 饲料与养殖现状
据统计, 全球有73%的饲料样品霉菌毒素超标。中国现有饲料加工企业12000多家, 饲料产量不低于2亿吨。大部分地区, 特别是长江以南地区, 夏季高温潮湿，饲料霉变及受霉菌毒素污染的现象非常普遍，其危害已是大问题。常见的有:曲霉菌属(主要分泌黄曲霉毒素、赭曲霉毒素等)、青霉菌属(主要分泌桔霉素等)、麦角菌属(主要分泌麦角毒素)、梭菌属(主要分泌呕吐毒素、玉米赤霉烯酮、T- 2毒素、Fumonisin毒素等)。
由于环境应激, 霉菌毒素之间的联合作用及饲料营养不平衡等因素的存在, 饲料中低含量的霉菌毒素即可对动物造成危害。例如， 当饲料中黄曲霉毒素含量为 14 . 0 g/ kg ( 低于美国鸡饲料黄曲霉毒素允许量 20 g/ kg 的卫生标准) 时即可对肉仔鸡生产性能造成严重影响。
二、 蒙脱石的作用
蒙脱石的名称来源于法国，法国做过一项动物研究，家兔回肠感染大肠杆菌后，服用蒙脱石可以减轻胃肠黏膜损伤，重建水电解质吸收，促进绒毛恢复正常形态，促进受损小肠黏膜上皮细胞的再生与修复。
霉菌毒素及各种细菌对Caco－2细胞均有不同程度的黏附作用，从而伤害胃肠黏膜，而蒙脱石能够阻断这种黏附，并且对病原菌黏附Caco－2细胞的阻断作用，要明显大于其对益生菌的阻断效果。例如，对大肠杆菌鼠伤寒沙门氏菌、嗜水气单胞菌 、副溶血弧菌黏附的阻断率，分别为54.22％ 48．41％ 60．53％ 50．64％， 而对两歧双歧杆菌、嗜酸乳杆菌黏附的阻断率，分别为25．64％和21．49％。结果显示：蒙脱石可有效阻断病原菌黏附胃肠道，从而防治肠道细菌感染和细菌移位，进而可以预防和治疗腹泻的发生。
牛业来等应用十六角蒙脱石治疗消化性溃疡及上消化道出血，病例30例皆取得满意疗效。由于蒙脱石可吸附各种病毒细菌及其他各种霉菌毒素，治疗断奶仔猪腹泻综合症总有效率为94.74%，治愈率为42.11%，高于氟哌酸(氟哌酸治疗总有效率为66.67%，治愈率27.77%)。
蒙脱石对猪，对人，对鸡鸭牛羊兔等动物的腹泻也有很好的疗效。在獭兔幼兔日粮中添加400g／t喹乙醇，与添3kg／t纳米蒙脱石，均有效减少了獭兔幼兔的腹泻次数，降低了腹泻率，效果上添加纳米蒙脱石组更明显。
三、 蒙脱石的作用机理
1、概念
粘土矿中蒙脱石含量大于80%就称为蒙脱石，蒙脱石为高纯度的膨润土，是膨润土的主要成分。这类矿物包括钠基蒙脱石、钙基蒙脱石 、镁基蒙脱石、铁基蒙脱石、锂基蒙脱石以及铝蒙脱石等。
蒙脱石硬度为2～2．5，相对密度2～2．7，甚柔软，有滑感。在电子显微镜下可见片状晶体，层与层之间可以滑动打开，层与层之间并不散乱分离，在水介质中可分散呈胶体状态，属酸性胶基，对强酸强碱具有一定的缓冲能力，因此能保持体系pH相对稳定。例如：蒙脱石在消化道延展，可形成连续的保护膜，与消化道黏液蛋白静电结合，可显著提高黏液的内聚力和弹性。( Girardeau，1987; Albengres等，1985) 。
2、结构
蒙脱石 ontmorillonite ，是天然硅铝酸盐，由二层共顶联接的硅氧四面体片，夹一层共棱联接的铝镁氧氢氧八面体片，构成2∶1型结构。晶层表面都是氧原子，没有氢氧原子组，晶层间没有氢键结合力，晶层间距为0. 96 ~ 2 . 14 nm，水分子和交换性阳离子可以进入层间，使晶格底面间距增大，蒙脱石体积膨大。例如：美国西部的钠基蒙脱石类粘土，其甲基蓝吸附能力 (仅表示阳离子交换能力 )可以高达 15 0 meq，遇水膨胀系数可以达到其遇水前体积的2 0倍。
在蒙脱石形成过程中，蒙脱石分子硅氧四面体中的S i4+可被 Al3+替换，铝氧八面体片中的 Al3+可被 Mg2+或Fe2 +替换。这种置换，经常造成八面体畸变，进而迫使四面体片作出旋转、伸长、歪扭等形式，来予以调正，直至出现断键，使多面体核心阳离子裸露，使晶层间产生永久性负电荷，为了平衡电荷，蒙脱石必须吸附环境中的阳离子到层间，而发生我们看到的离子交换作用，主要阳离子如Na+、Ca2+、K+、Mg2+、Li+、H+、Al3+等(杨献忠等，2003) 。正是这种离子交换特性大大增强了蒙脱石吸附霉菌毒素的功能。
3、负电吸附特性
蒙脱石晶层间的永久性负电荷，产生静电引力和非稳态电位固定效应，使蒙脱石吸附具有选择性，即有效吸附各种霉菌毒素，而吸附弱极性的营养成分甚微。许多霉菌毒素, 如黄曲霉毒素、 玉米赤霉稀酮等的分子结构中含有极性基团，如: O H, C O,N H2，或含有可极化的基团，如: C C , C6H5 等，能被蒙脱石优先吸附。例如：呈刚性平面分子结构的黄曲霉毒素，能进入蒙脱石的内表面，与晶层间可交换性阳离子产生强烈的相互作用，并且不易解吸，表现出较高的吸附效率和吸附稳定性。吸附量随黄曲霉毒素含量的增加而增加，两者呈直线相关。当吸附反应体系中赖氨酸含量为0．2％—0．4％时，不影响蒙脱石对黄曲霉毒素的吸附。
蒙脱石矿物层间区域具有层间交换、 层间吸附、 层间催化、 层间聚合、 层间柱撑等特性。霉菌毒素分子在蒙脱石矿物层间区域可发生分子吸附、 氢键吸附、 不可逆交换吸附、 质子化吸附及吸附分解模式。例如，蒙脱石边面上未完全配位的铝离子能与黄曲霉毒素上的 - 羰基进行化学吸附而形成稳定复合物，因而降低了黄曲霉毒素的生物有效性。
并且，透射电镜分析表明吸附原毒素前后蒙脱石的粒径没有明显改变，XRD分析证实，吸附原毒素后蒙脱石层间距没有发生变化。“车厢式”结构的蒙脱石，将毒素固定到蒙脱石分子的“车厢”中，从而使毒素在体内失活。
4、表面吸附力
蒙脱石颗粒细小，0．2～1 m，颗粒表面积巨大，颗粒遇液体分散后引起有效表面积进一步增大，蒙脱石每克粉剂可覆盖100～110m2消化道表面，由于层间域的存在，不仅具有巨大的外表面积，也有巨大的内表面积，其比表面积可达 600 ~800 m，2/ g。所以蒙脱石比表面积大，表面能很高，表面吸附力超强。蒙 脱石 的 吸 附 机理 说 明 图：
其中左 A 是未膨胀的蒙脱石矿物示意图。右 B 是集合颗粒遇液体后单个片状体之间膨胀而引起有效表面积增大，吸附示意图。
四、总结
蒙脱石所具有的层纹片状结构，非均匀性电荷分布，巨大的表面积和阳离子交换能力等特点，使其即有色散力又有静电力，色散力易吸附非极性分子, 静电力易吸附极性、不饱和及易极化的分子，从而对饲料中的霉菌毒素有较好的吸附能力。浙江大学饲料科学研究所测试,纳米蒙脱石对霉菌毒素吸附力(%) 如下: 黄曲霉毒素,100%; 玉米赤霉烯酮,87%;赭曲霉毒素,70%;麦角毒素,100%;串珠镰孢菌毒素,91%。
蒙脱石能增加消化道黏液的质和量，加强黏膜的屏障作用，保护和修复消化道黏膜；能吸附并固定消化道黏膜上的病原微生物于分子内，使其破裂脱水以至灭活；同时能在胃肠道中吸附其所产生的毒素，随粪便排出体外。从而抵抗外来制病因子的侵入，防止腹泻。
蒙脱石脱毒量大，作用力强，稳定性好，主要取决于它的吸附性能和胶凝特性。
五、 参考文献
1 齐德生，刘凡，于炎湖． 蒙脱石对黄曲霉毒素B1的吸附作用［J］矿物学报，2004，24( 4) :341～346．
2 胡秀荣，吕光烈，陈林深，等． 天然蒙脱石与细菌相互作用机理的研究［J］． 药学学报，2002，37( 9) :718～720．
3 胡彩虹，夏枚生，熊莉，等． 蒙脱石对细菌黏附Caco-2细胞的影响［J］． 细胞生物学杂志，2006，28( 1) :76～78．
4 夏枚生，胡彩虹，赵文艳． 载铜蒙脱石的抗菌机理研究［J］． 微生物学报，2006，46( 3) :432～435．
5 韩秀山，吕大丰，黄周可，等． 蒙脱石对细菌的吸附作用［J］． 吉林畜牧兽医，2007，28( 1) :23～24．
6 姬洪张如柏． 纳米级的轴长1．8nm蒙脱石药理作用的矿物学解释J ． 矿物岩石2002 .22 .3 .98－100．
7 翟永功左明雪．药用矿物蒙脱石的红外光谱分析J ．中草药2001 9 837－838．
8 陈况陈淑洁姒健敏等． 不同产地的天然蒙脱石对大鼠慢性萎缩性胃炎治疗作用的比较J ．中国新药杂志2007. 16. 4. 296－299．
9 胡秀荣吕光烈陈林深等． 天然蒙脱石与细菌相互作用机理的研究J ． 药学学报2002 .3.9 .718－720．
10 周学永陈守文吴新世等． 苏云金芽胞杆菌原毒素在蒙脱石上的吸附特性研究J ． 农业环境科学学报2006 .25. 4 .992－996．
11 陈奕王佩吴洪海等． 蒙脱石止泻作用的实验研究J ．中国新药与临床杂志1999 .18 .4 .230－232．
12 刘海军李兆申许国铭等． 十六角蒙脱石对大鼠急性胃粘膜损伤的预防和治疗作用 J ． 中国新药与临床杂志1996.15. 5. 260－263．
13 牛业来庞辉李玉杰． 十六角蒙脱石治疗消化性溃疡并上消化道出血30例J ． 中国基层医药2001. 8. 1. 82．
14 孟玉良许家亮．蒙脱石的药用机理及毒理性J ．山东畜牧兽医2010 .4 .77－78．
15 林飞宏． 蒙脱石防治仔猪腹泻的效果及其机理探索D．重庆西南大学2007．
16 粘土矿物灯霉菌毒素吸附剂及其主要区别.周慧堂
The English version
A, feed and breeding
According to statistics, 73% of the world's excess sample feed mycotoxins. More than 12000 Chinese existing feed processing enterprises, not less than 200 million tons of feed production. Most of the region, especially the area south of the Yangtze river, summer heat and damp, feed mildew and contaminated with mycotoxins phenomenon is very common, the harm is big problem. Common are: aspergillus species (mainly secreted aflatoxin, ochre and aspergillus toxin, etc.) and penicillium (mainly secreted citrinin, etc.), claviceps (mainly secreted ergot toxins), fusobacterium (mainly secreted vomiting toxins, corn gibberellic ketene, T 2 toxin, Fumonisin toxin, etc.).
Due to environmental stress, mycotoxin combination and feed nutrition imbalance between the existence of factors such as feed low levels of mycotoxin can cause harm to animals. For example, when the aflatoxin content in the feed for 14. 0 g/kg (below the chicken feed aflatoxin allowances the hygiene standards of 20 g/kg) is activated when a serious effects production performance of broiler chickens.
Second, the action of montmorillonite
Montmorillonite name comes from France, France made a animal study, rabbit ileum after infected with e. coli, taking montmorillonite can reduce gastric mucosa damage, reconstruction of water electrolyte absorption, promote hair returned to normal forms, promote the regeneration of the damaged small intestinal mucosa epithelial cells and repair.
Mycotoxin and optimization of various bacteria on Caco - 2 cells have different levels of adhesion, which damage the gastrointestinal mucosa, and montmorillonite can block the adhesion, and optimization of pathogenic bacteria adhesion Caco - 2 cells blocking effect, significantly greater than the blocking effect of probiotics. , for example, e. coli, salmonella typhimurium, moisture, deputy hemolytic bacterium vibrio adhesion blocking rate, 54.22% 60.53% 54.22% and 48.41%, respectively, and the discrepancy of bifidobacterium and lactobacillus acidophilus adhesion blocking rate, at 25.64% and 21.49% respectively. Results show that montmorillonite can effectively block the pathogenic bacteria adhesion of gastrointestinal tract, and prevention and treatment of intestinal bacteria infection and bacterial translocation, which can prevent and treat diarrhea.
Industry applications such as ten hexagonal montmorillonite treatment of peptic ulcer and upper gastrointestinal bleeding, 30 cases were satisfactory curative effect. Because of montmorillonite is adsorption various virus, bacteria, and other various mycotoxins, treatment of weaned piglets diarrhea syndrome, the total effective rate was 94.74%, the cure rate was 42.11%, higher than that of gatifloxacin (norfloxacin treatment the total effective rate was 66.67%, the cure rate 27.77%).
Montmorillonite to pigs, to people, cattle and sheep to chickens and ducks diarrhea also has a good curative effect of rabbits and other animals. In rabbit immature rabbit diet can add 400 g/t olaquindox, and add 3 kg/t nano montmorillonite, are effectively reduced the immature rabbit saw the number of diarrhea of otter, reduce the diarrhea rate, effect on adding nanometer montmorillonite group is more obvious.
Third, the mechanism of the montmorillonite
1, concept,
Clay minerals in the montmorillonite content greater than 80% is called montmorillonite, montmorillonite is highly purified bentonite, bentonite is the main component. Such minerals including sodium based montmorillonite, calcium montmorillonite, magnesium based montmorillonite, iron-based montmorillonite, lithium montmorillonite and aluminum montmorillonite, etc.
Montmorillonite hardness is 2 ~ 2.5, the relative density of 2 ~ 2.7, very soft, slippery feeling. By electron microscopy in crystal plate, can slide open between layer and layer, are not scattered between layer and layer separation, in colloidal state can be dispersed in water medium, belongs to the acid base glue, have certain buffering capacity to acid alkali, thus to maintain a system of pH is relatively stable. For example: montmorillonite in the digestive tract, can form the protective film of continuous, combine with the digestive tract mucous protein electrostatic, can significantly increase the cohesion of mucus and elasticity. (Girardeau, 1987; Albengres etc., 1985).
2, structure,
Montmorillonite ontmorillonite, is the natural sialic acid salt, by the top connection of the silicon oxygen tetrahedron on the second floor, a layer of common edge clamp connection of the aluminum magnesium hydroxide oxygen octahedron, constitute a 2:1 type structure. Crystal layer surface are oxygen, no hydrogen atomic groups, no hydrogen bond between crystal layer binding force, crystal layer spacing of 0. 96 ~ 2. 14 nm, water molecules and may enter the interlayer exchangeable cations, make lattice floor spacing increases, the volume of montmorillonite). In the western United States, for example, sodium based montmorillonite clay, the methylene blue adsorption capacity (said only cation exchange capacity) can be as high as 15 0 meq, encounter water expansion coefficient can reach its encounter water volume 2 0 times before.
In the process of montmorillonite to form, montmorillonite molecules in the silicon oxygen tetrahedron i2 + S can be replaced by Al3 +, aluminium oxide octahedron of Al3 + can be replaced by magnesium 2 + and Fe2 +. The displacement, often cause octahedral distortion, forcing tetrahedron pieces to rotate, elongation, crooked and form, to be reset, until a broken key, make solid core cationic naked, make the crystal layer between produces permanent negative charge, in order to balance charge, montmorillonite must of cation adsorption environment to the interlayer, and the ion exchange, we see the main cations such as Na +, Ca2 +, K +, magnesium 2 +, Li +, H +, Al3 + (xian-zhong Yang, etc., 2003). It is this ion exchange properties greatly enhances the montmorillonite adsorption function of mycotoxin.
3, negatively charged adsorption properties
Montmorillonite crystal layer between the permanent negative charge, produce electrostatic attraction and unsteady potential fixed effects, make the montmorillonite selective adsorption, namely effective mycotoxin, adsorption and adsorption little nutrition ingredient of weak polarity. Many mycotoxins such as aflatoxin, corn gibberellic is contained in the molecular structure of the dilute acetone etc polar groups, such as: O, H, O, C N H2, or contains polarizable groups, such as C, C C6H5, etc., can be montmorillonite preferential adsorption. For example: the molecular structure of rigid plane of aflatoxin, can enter the inner surface of montmorillonite, the interchangeability between the crystal layer and cationic produce strong interaction, and not easy desorption, showed higher adsorption efficiency and stability. Adsorption quantity increases with the increase of content of aflatoxin, both in a straight line. When the adsorption in the reaction system of lysine content is 0.2%, 0.4%, do not affect montmorillonite adsorption of aflatoxin.
Interlayer montmorillonite mineral area has interlayer, interlayer exchange adsorption, catalysis, between layer character such as polymerization, interlayer between column brace. Mycotoxin molecules in the layer of montmorillonite mineral area can occur between molecular absorption, hydrogen bond exchange adsorption, adsorption and irreversible proton adsorption and adsorption decomposition model. Montmorillonite edge, for example, can not completely ligand on the surface of aluminum ions and aflatoxin - carbonyl chemical adsorption and form stable complexes, and thus reduce the biological effectiveness of aflatoxin.
And transmission electron microscopy (sem) analysis showed that adsorption of montmorillonite before and after the original toxin size there is no obvious change, XRD analysis confirmed that the adsorption of the original toxins after the montmorillonite layer spacing has not changed. "CheXiangShi" structure of montmorillonite, toxins will be fixed to the montmorillonite molecules "car", so that the toxins in the body.
4, surface adsorption
Montmorillonite particles small, 0.2 ~ 1 m, particle surface area is huge, particles in the liquid dispersion caused by effective surface area increases further, montmorillonite powder covering 100 ~ 110 m2 per gram surface of the digestive tract, as a result of the existence of interlayer domain, not only has large surface area, there are large internal surface area, the specific surface area of up to 600 ~ 800 m, 2 / g. So the montmorillonite is greater than surface area, high surface energy, surface strong adsorption force. The adsorption mechanism of montmorillonite Ming said:
Which left A is not the expansion of the montmorillonite mineral diagram. B is right after the collection of particles in the liquid between individual lamellar body expansion caused by the effective surface area increases, adsorption.
Four,
Montmorillonite layer lines of lamellar structure, heterogeneity, charge distribution, large surface area and cation exchange capacity, etc, make its have the dispersion force and electrostatic force, dispersion force is easy to adsorb nonpolar molecules, electrostatic force easily adsorption polarity, unsaturated and polarized molecules, thus mycotoxins in feed has good adsorption capacity. Test feed science research institute, zhejiang university, nanometer montmorillonite on the mycotoxin adsorption force (%) as follows: yellow aspergillus toxin, 100%; Corn gibberellic ketene, 87%; Ochre and aspergillus toxin, 70%; Ergot toxin, 100%; Fusarium toxins, beaded 91%.
Montmorillonite can increase the quantity and quality of the digestive tract mucous, strengthen the mucous membrane barrier function, protect and restore gastrointestinal mucous membrane; Can adsorption and fixed on the digestive tract mucosa of pathogenic microorganisms in the molecule, the broken dehydration and inactivated; At the same time can be adsorbed in the gastrointestinal tract the toxin, produced by the faeces. To resist the invasion of the foreign system of disease factor, prevent the diarrhoea.
Large amount of montmorillonite detoxification, strong force, good stability, mainly depends on its adsorption performance and gelling properties.
Five, the references
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