|
 
霉菌毒素在動(dòng)物飼料、飼料原料和人類食品中廣泛存在，它是由霉菌在農(nóng)產(chǎn)品中產(chǎn)生的一系列具有廣泛化學(xué)結(jié)構(gòu)的有毒次級(jí)代謝產(chǎn)物。霉菌毒素污染不僅可造成畜牧業(yè)經(jīng)濟(jì)損失，部分霉菌毒素還具有致癌性或致畸胎性，且可在動(dòng)物的肉、蛋、奶中殘留，由食物鏈進(jìn)入人體，對(duì)人類健康構(gòu)成嚴(yán)重威脅。
我國(guó)霉菌毒素污染比較嚴(yán)重，動(dòng)物采食被霉菌毒素污染的飼料可引起一些疾病。因此，飼料霉菌毒素感染已成為飼料工業(yè)和畜牧業(yè)不可忽視的問(wèn)題，消除霉菌毒素，對(duì)保證動(dòng)物健康，充分發(fā)揮動(dòng)物的生產(chǎn)潛能降低經(jīng)濟(jì)損失有重大意義。而與其他家畜比較，豬的飼養(yǎng)管理最為粗放，因而豬的飼料中毒病，在各種家畜中發(fā)病概率最高，其造成的經(jīng)濟(jì)損失也最大。
1 霉菌毒素的產(chǎn)生與分類
對(duì)畜禽養(yǎng)殖業(yè)危害較大的霉菌毒素主要是由以下四種霉菌屬所產(chǎn)生：曲霉菌屬（主要分泌黃曲霉毒素AFT、赭曲霉毒素等），青霉菌屬（主要分泌桔霉素），鐮刀菌屬（主要分泌T-2毒素、嘔吐毒素DON、玉米赤霉烯酮、伏馬毒素等），麥角菌屬（主要分泌麥角毒素）。
迄今為止已經(jīng)有超過(guò)300種霉菌毒素被分離和鑒定出來(lái)，上述的幾種毒素即為現(xiàn)今普遍認(rèn)識(shí)的8種主要毒素。
2 霉菌毒素的作用機(jī)理
霉菌毒素影響廣泛，從動(dòng)物的急性死亡，慢性死亡到生長(zhǎng)緩慢和繁殖性能降低。攝入一定量的霉菌毒素可削弱其免疫力，降低動(dòng)物對(duì)傳染性疾病的抵抗力，可使動(dòng)物臟器損傷（如肝臟、腎臟、胃腸道和繁殖器官等），繁殖性能下降，并且在動(dòng)物性產(chǎn)品中殘留，對(duì)人類健康造成危害。
霉菌毒素中毒主要是動(dòng)物食入了被毒素污染的飼料，日糧中營(yíng)養(yǎng)成分不足，缺乏蛋白質(zhì)、硒和維生素也是引起霉菌毒素中毒的因素之一。由于大多數(shù)常見(jiàn)霉菌毒素的中間產(chǎn)物或終產(chǎn)物的毒性與霉菌毒素的毒性不同，因此減少或增加外源性的化合物、代謝的藥物可影響機(jī)體對(duì)毒素的反應(yīng)，這類藥物對(duì)黃曲霉毒素和赭曲霉毒素的作用比較大，而對(duì)單端孢霉毒素相對(duì)比較小。
通常飼料中霉菌毒素不是單一存在而是兩種或幾種同時(shí)存在，當(dāng)不同毒素同時(shí)存在時(shí)，霉菌毒素的毒性會(huì)可能出現(xiàn)加性效應(yīng)、亞加性效應(yīng)、協(xié)同效應(yīng)、增效效應(yīng)和頡頏效應(yīng)。加性效應(yīng)（Synergistic effects）是指2種霉菌毒素的組合作用等于二者單一作用的累積相加。亞加性效應(yīng)（Less than additive effects）是指發(fā)生于2種霉菌毒素的組合作用低于二者單一作用的累積相加。協(xié)同效應(yīng)（Synergistic effects）指2種霉菌毒素的組合作用高于二者單一作用的累積相加。增效效應(yīng)（Potentiate effects）指一種霉菌毒素對(duì)某組織或器官不產(chǎn)生毒性作用，但攝人另一霉菌毒素后，前者使后者毒性增強(qiáng)。頡頏效應(yīng)（Antagonistic effects）是指一種霉菌毒素干擾另一種霉菌毒素的毒性作用，這種情況較少見(jiàn)。
2.1 黃曲霉毒素
黃曲霉毒素（aflatoxin，簡(jiǎn)稱為AF）在各霉菌毒素中，被認(rèn)為毒性最強(qiáng)，危害最大的致癌物質(zhì)，其耐熱性強(qiáng)，超過(guò)80℃才能破壞，在紫外線照射下能產(chǎn)生熒光，是黃山霉菌和寄生曲霉菌的產(chǎn)物，幾乎所有動(dòng)物對(duì)AF都敏感，禽類最為敏感。AF對(duì)幼齡動(dòng)物的毒性強(qiáng)，致死率高，而成年動(dòng)物的耐受力較強(qiáng)。黃曲霉菌（AF）可分為黃曲霉菌B1、B2、G1、G2、M1、M2 ，其中危害最大，毒性最強(qiáng)的是黃曲霉菌B1 （簡(jiǎn)稱為AFB1），對(duì)動(dòng)物的主要影響是致腫瘤、免疫抑制、致突變和致畸，影響的主要靶器官是肝臟，是一種肝毒素，可引起肝臟出血、肝臟脂肪變性、膽管增生等，并可導(dǎo)致肝癌的發(fā)生（徐運(yùn)杰等，2008；胡蘭等，2001）。
黃曲霉毒素是養(yǎng)豬生產(chǎn)中危害最嚴(yán)重的毒素，對(duì)豬的危害主要有
（1）是最強(qiáng)的免疫抑制劑，當(dāng)豬采食受其污染的飼料后，首先免疫系統(tǒng)受到干擾，對(duì)疫病易感性提高，藥物治療效果差。
（2）是凝血因子抑制劑，表現(xiàn)在傷處長(zhǎng)時(shí)間流血不止及漿膜下層淤斑出血，小腸和結(jié)腸出血等。
（3）侵害肝臟，致使肝功能下降，肝臟腫大，膽汁分泌減少，導(dǎo)致飼料中蛋白質(zhì)和脂肪利用率下降（李夢(mèng)云等，2005）。研究表明：生長(zhǎng)育肥豬日糧中含黃曲霉毒素200-400μg／kg時(shí)，豬生長(zhǎng)受阻和飼料報(bào)酬降低；含400-800μg／kg時(shí)，造成肝臟顯微損傷，膽管炎、肝炎，有免疫抑制作用；含800-1200μg／kg時(shí)，生長(zhǎng)受阻，采食量減少，被毛粗糙，黃疸，低蛋白血癥；含1200-2000μg／kg時(shí)，表現(xiàn)為黃疸，凝血病，精神沉悶，厭食，部分死亡（閆甫等，2007）。
2.2 赭曲霉毒素
赭曲霉素（Ochratoxin，簡(jiǎn)稱OCT）是由曲霉屬及青霉屬中的某些菌種產(chǎn)生的一類結(jié)構(gòu)相似的有毒次生代謝產(chǎn)物，其中以赭曲霉毒素A（Ochratoxin A，簡(jiǎn)稱OTA）的毒性最強(qiáng)。其毒性與黃曲霉毒素相當(dāng)，腎是其主要的靶器官，是一種腎毒素，赭曲霉毒素A幾乎對(duì)所有的動(dòng)物都有腎毒性。尤其是人類，低攝入量時(shí)可造成生殖性能下降。研究表明，OTA對(duì)所有的單胃哺乳動(dòng)物均有腎毒性，可引起動(dòng)物腎萎縮或腫大、顏色變灰白、皮質(zhì)表面不平及斷面可見(jiàn)皮質(zhì)纖維性變；
顯微鏡下可見(jiàn)腎小管萎縮、間質(zhì)纖維化、腎小球透明變性和腎小管環(huán)死等，并伴有尿量減少、血中尿素氮升高、對(duì)氨基馬尿酸清除降低、尿頻、尿蛋白和尿糖增加等腎功能損害（李鵬等，2009）。試驗(yàn)表明給豬飼喂含赭曲霉毒素1mg/kg的飼料3個(gè)月，可引起腹瀉、厭食和脫水，出現(xiàn)生長(zhǎng)遲緩，飼料利用率低，剖檢多見(jiàn)腎蒼白、堅(jiān)硬，即橡皮腎。除腎毒性外，OTA還有肝毒性、抑制免疫、致畸和致癌性。在生殖毒性方面，對(duì)于雄性動(dòng)物而言，赭曲霉毒素A還可以使公豬精液品質(zhì)下降（Biroeta1，2003）。
2.3 桔青霉素
桔青霉素（Citrinin）是青霉屬和曲霉屬的某些菌株產(chǎn)生的真菌毒，是一種腎毒素，它能引起豬、雞、鴨和鳥(niǎo)類等幾乎所有動(dòng)物發(fā)生腎臟病變，但急性毒性在不同的品種之間有所差異。對(duì)鴨來(lái)說(shuō)，半致死劑量是57mg／kg；雞是95mg／kg；兔子是134mg／kg。桔青霉素與赭曲霉毒素A有協(xié)同作用，可抑制鼠科動(dòng)物腎臟RNA的合成，小麥、燕麥、黑麥、大麥、玉米、稻谷等都可生長(zhǎng)桔青霉素（劉仁榮等，2004）。
2.4 單端孢霉烯族毒素
單端孢霉烯毒素是由鐮刀菌屬產(chǎn)生的結(jié)構(gòu)相似的一類化合物的總稱，種類超過(guò)148種，其中主要代表有：T-2毒素（T-2 toxin）、二乙�；s草鐮刀菌烯醇（DAS）和脫氧雪腐烯醇。主要損害動(dòng)物的肝臟和腎臟，而且大多屬于組織刺激因子和致炎物質(zhì)。T-2毒素主要作用于細(xì)胞分裂旺盛的組織器官，如胸腺、骨髓、肝、脾、淋巴結(jié)、生殖腺及胃腸粘膜等，抑制這些器官細(xì)胞蛋白質(zhì)和DNA合成，并造成神經(jīng)機(jī)能損害。
T-2毒素或DAS會(huì)損傷禽類的消化道粘膜，引起口腔潰瘍，一般臨床癥狀表現(xiàn)為食欲減退或喪失，胃腸炎癥，出血，嘔吐，免疫機(jī)能降低等（Kubena等，1994）。豬對(duì)DON最敏感，主要導(dǎo)致豬食欲減退、拒食、嘔吐和胃腸道損傷。許多研究顯示：當(dāng)日糧DON水平達(dá)3-5mg/kg時(shí)，豬的食欲大大減退，生長(zhǎng)和生產(chǎn)性能下降。當(dāng)生長(zhǎng)育肥豬采食含有14mg/kg DON的飼料后，10~20min即會(huì)出現(xiàn)嘔吐，不正常的焦慮和磨牙現(xiàn)象，DON對(duì)泌乳母豬的影響更嚴(yán)重，由于食欲不振導(dǎo)致母豬的泌乳量減少，從而導(dǎo)致仔豬生長(zhǎng)速度緩慢。
另項(xiàng)研究表明：DON含量在0-14mg/kg的試驗(yàn)中，飼糧中每增加1mg/kg DON，生長(zhǎng)肥育豬的采食量減少6％，含毒量超過(guò)10mg/kg時(shí)，即完全拒食（Trenholm等，1994）。飼料攝入量降低與飼料中DON濃度升高呈線性關(guān)系。其它的單端孢霉烯族毒素對(duì)反芻動(dòng)物的健康或生產(chǎn)性能無(wú)影響（侯然然等，2007）。研究還表明T-2毒素對(duì)不同動(dòng)物的毒性還有一定種屬差異，新生或未成年動(dòng)物比成年動(dòng)物對(duì)毒素更敏感，雄性動(dòng)物比雌性動(dòng)物也要敏感（霍星華等，2008）。
2.5 玉米赤霉烯酮
玉米赤霉烯酮是鐮刀霉菌通過(guò)聚酮途徑合成的對(duì)哺乳動(dòng)物具有雌激素樣效應(yīng)的一類次級(jí)代謝產(chǎn)物。適宜的條件下，所有的谷物類作物或飼料產(chǎn)品都可受到玉米赤霉烯酮的污染。豬對(duì)玉米赤霉烯酮最敏感，而受影響最大的部位是其生殖系統(tǒng)。由于玉米赤酶烯酮具有類雌激素作用，低于l mg／kg時(shí)導(dǎo)致動(dòng)物表現(xiàn)出雌性化特征，公豬會(huì)表現(xiàn)睪丸萎縮，乳頭增大的雌性特征。
對(duì)于母豬而言，含量過(guò)高可以引起排卵、假懷孕、胎兒發(fā)育等，臨床特征也表現(xiàn)為外陰充血、水腫、乳房腫大和乳頭肥大、嚴(yán)重時(shí)可造成陰道和直腸脫（郭成志等，2010）。玉米赤酶烯酮能與類固醇合成相關(guān)酶反應(yīng)，影響類固醇的形成，干擾內(nèi)分泌系統(tǒng)，它長(zhǎng)期的效應(yīng)和對(duì)后代的毒性效應(yīng)有待進(jìn)一步研究。
2.6 伏馬毒素
伏馬菌素是由鐮刀菌屬產(chǎn)生的水溶性代謝產(chǎn)物，是一類由不同的多氫醇和丙三羧酸組成的結(jié)構(gòu)類似的雙酯化合物。其中FB1毒性最強(qiáng)，是近年來(lái)發(fā)現(xiàn)的能損傷免疫系統(tǒng)、肝腎，降低動(dòng)物生產(chǎn)力甚至引起動(dòng)物死亡的一種霉菌毒素。伏馬菌素與豬肺水腫�。≒PE）有關(guān)，導(dǎo)致豬肺毛細(xì)血管上皮細(xì)胞的變化，呼吸障礙，心臟機(jī)能損傷（Diaz等，1994），而對(duì)馬來(lái)說(shuō)，伏馬菌素可引起腦白質(zhì)液化性壞死（ELEM）、大腦皮層損傷、共濟(jì)失調(diào)、局部麻痹、神情冷漠、運(yùn)動(dòng)功能削弱等，還會(huì)引起羊肝腎病變（王少康，2003
），另外小劑量的嘔吐毒素和伏馬毒素可以激活許多免疫反應(yīng)，如細(xì)胞因子表達(dá)增加。
結(jié)合上述霉菌毒素的毒性機(jī)制，可以得出霉菌毒素中毒主要表現(xiàn)在對(duì)動(dòng)物免疫系統(tǒng)、胃腸道、肝臟、腎臟及生殖系統(tǒng)等的影響。表3給出不同霉菌毒素對(duì)豬機(jī)體的毒性水平。由表可以看出霉菌毒素對(duì)豬的免疫機(jī)能、繁殖能力、采食量和肝臟腎臟都有影響，并且每一種毒素對(duì)各機(jī)能的影響程度不同。
3 霉菌毒素對(duì)全國(guó)飼料的污染情況
根據(jù)聯(lián)合國(guó)糧農(nóng)組織（FAO）資料，全世界每年約有25％的谷物不同程度地受到霉菌毒素的影響，約2%的農(nóng)作物因污染嚴(yán)重而失去營(yíng)養(yǎng)價(jià)值和經(jīng)濟(jì)價(jià)值。對(duì)中國(guó)28個(gè)省市自治區(qū)194份飼料及原料玉米、麥麩的調(diào)查結(jié)果顯示，DON、T-2毒素和ZEN的污染率分別為50.0%、18.1%和26%（計(jì)成等，2007）。動(dòng)物性原料魚(yú)粉同時(shí)被多種霉菌毒素污染的情況也很普遍，霉變的飼料被動(dòng)物采食后，毒素及其代謝產(chǎn)物可殘留在畜產(chǎn)品及其加工制品中，通過(guò)食物鏈進(jìn)入人體，這些具有極強(qiáng)致病及致癌作用的毒素嚴(yán)重威脅人類的健康。
敖志剛等（2008）發(fā)現(xiàn)副產(chǎn)品原料，特別是玉米副產(chǎn)品如干燥酒糟（DDGS）和玉米蛋白粉中霉菌毒素的污染非常嚴(yán)重，并且飼料原料和全價(jià)飼料中多種霉菌毒素往往同時(shí)存在，由于不同毒素間具有協(xié)同作用，將加劇毒素的毒性作用和中毒癥狀的嚴(yán)重程度。張丞等（2009）對(duì)2009年上半年中國(guó)飼料和原料抽樣調(diào)查的結(jié)果顯示，在90份樣品中，完全沒(méi)有檢測(cè)出霉菌毒素的樣品僅8份，占樣品總數(shù)的8.9％；只檢測(cè)到1種霉菌毒素的樣品數(shù)為7份，占樣品總數(shù)的7.8％；同時(shí)檢測(cè)到含4種以上霉菌毒素的樣品數(shù)占67.8％。黃廣明等（2010）分析了我國(guó)2008年、2009年和2010年從多個(gè)省市的飼料廠及養(yǎng)殖場(chǎng)客戶采集飼料原料及配合飼料樣品，結(jié)果發(fā)現(xiàn)，在我國(guó)大部分地區(qū)，玉米赤霉烯酮和嘔吐毒素的污染情況較嚴(yán)重，尤其是2009年和2010年。
4 豬霉菌毒素中毒的預(yù)防
飼料中各種霉菌毒素之間有協(xié)同作用，幾種霉菌毒素協(xié)同作用對(duì)動(dòng)物健康和生產(chǎn)性能的影響比任何一種霉菌毒素單獨(dú)作用都要大。使豬群中毒時(shí)臨床癥狀更為復(fù)雜，特別是當(dāng)有細(xì)菌性和病毒性因素存在的情況下尤為突出。因而，在臨床上多種霉菌毒素和細(xì)菌、病毒混合感染引起豬群中毒的診斷變得更為困難。豬霉菌毒素中毒診斷比較困難，中毒后的治療效果不理想，豬場(chǎng)應(yīng)提前采取有效措施加以預(yù)防。
4.1 飼料防霉措施
飼料的防霉要從源頭做起，增強(qiáng)抗霉菌植物的培育、選用抗霉菌品系、加強(qiáng)田間管理。對(duì)于無(wú)法避免的污染，在收獲和儲(chǔ)藏的過(guò)程中應(yīng)選擇合適的收獲時(shí)間、儲(chǔ)藏在溫度和濕度合適的場(chǎng)所。需要嚴(yán)格控制飼料原料的水份含量。水分是決定飼料中霉菌能否生長(zhǎng)的一個(gè)最主要因素。
理想的物料中含水量應(yīng)不超過(guò)12％，含水量>l5％時(shí)可致霉菌生長(zhǎng)和大量繁殖，飼料含水l7％~ 18％為真菌繁殖產(chǎn)毒的最適條件。保持設(shè)備清潔，不僅控制病原菌，而且要控制和減少霉菌和霉菌毒素在飼料生產(chǎn)設(shè)備內(nèi)生長(zhǎng)。必要時(shí)添加防霉劑，這即經(jīng)濟(jì)又可大量獲得的防霉劑主要為短鏈脂肪酸，如甲酸、乙酸和丙酸，目前最常用的防霉劑是丙酸鹽，包括丙酸鈉、丙酸鈣、丙酸銨和二丙酸銨。
丙酸鹽具有對(duì)飼料設(shè)備無(wú)腐蝕、穩(wěn)定和在飼料中長(zhǎng)期起防霉作用的優(yōu)點(diǎn)。需要指出的是，防霉劑可以抑制霉菌的生長(zhǎng)，而對(duì)飼料或飼料原料中已經(jīng)存在的霉菌毒素不起任何作用。
4.2 霉變飼料的脫毒處理
化學(xué)方法
堿處理、臭氧處理、氨處理法以及一甲胺和氫氧化鈣處理可能有一定的效果。臭氧是一種對(duì)雙鍵物質(zhì)有優(yōu)先作用效果的強(qiáng)氧化劑。臭氧可在體外通過(guò)化學(xué)反應(yīng)降解AFB1、AFGl、AFB2和AFG2，這一點(diǎn)已經(jīng)通過(guò)試驗(yàn)證實(shí)。
何祖平等用碳酸氫鈉、次氯酸鈉、氫氧化鈉和氯化鈉對(duì)青霉酸進(jìn)行脫毒，碳酸氫鈉、次氯酸鈉和氫氧化鈉具有一定的脫毒效果。重亞硫酸鈉與AF反應(yīng)生成水溶性產(chǎn)物，從而解除AF的毒性。應(yīng)當(dāng)注意的是這種方法只對(duì)某種毒素有效，并不是全都能降解，另外這些化學(xué)品在飼料中的殘留問(wèn)題無(wú)法有效和經(jīng)濟(jì)的解決，因此不太實(shí)用，且存在危險(xiǎn)。
吸附劑的使用
用來(lái)控制飼料或食品中霉菌毒素最常用的方法是使用霉菌毒素吸附劑。大多數(shù)霉菌毒素吸附劑通過(guò)降低霉菌毒素質(zhì)量濃度而減少其進(jìn)入血液和靶細(xì)胞的機(jī)會(huì)，從而起到有效防止霉菌毒素產(chǎn)生毒害的作用。主要包括無(wú)機(jī)鹽類吸附劑及有機(jī)霉菌毒素吸附劑兩大類。
然而，各種吸附物質(zhì)對(duì)不同種毒素的吸附能力和吸附的效果都各不相同，而同時(shí)使用多種吸附劑復(fù)合使用是否能達(dá)到預(yù)期的那種吸附效果疊加的效應(yīng)應(yīng)該做試驗(yàn)加以論證。因此，在實(shí)際生產(chǎn)中，飼料、原料霉變中毒的情況依舊嚴(yán)重。且吸附劑不僅吸附霉菌毒素，也吸附飼料中的小分子物質(zhì)，如生物素，從而引發(fā)母豬肢蹄病。
5 豬霉菌毒素中毒的修復(fù)
豬霉菌毒素中毒后，由于侵害的是肝臟、腎臟等功能性器官與免疫系統(tǒng)的抑制，幾乎沒(méi)有很好的方法進(jìn)行治愈，這與人類患脂肪肝、肝硬化的治療是同一個(gè)道理，核心在于減輕臟器負(fù)擔(dān)和盡量修復(fù)其功能。
我們以肝臟修復(fù)為例：
肝臟是動(dòng)物體內(nèi)最為復(fù)雜的器官之一，承擔(dān)著蛋白質(zhì)、糖類及脂類的合成、分解與儲(chǔ)存，尤其是脂質(zhì)代謝，肝臟合成脂蛋白，有利于脂質(zhì)運(yùn)輸，也是脂肪酸氧化和酮體形成的主要場(chǎng)所。正常時(shí)肝含脂質(zhì)量不多，約為4％，其中主要是磷脂。若肝臟不能及時(shí)將脂肪運(yùn)出，脂肪在肝細(xì)胞中堆積，即形成脂肪肝。在肝臟堆積的脂肪，可影響肝細(xì)胞功能，破壞肝細(xì)胞，使結(jié)締組織增生，造成肝硬變。
而各種營(yíng)養(yǎng)物質(zhì)的合成代謝都需要依靠相應(yīng)的酶、維生素、活性物質(zhì)等活性因子來(lái)完成，而這些活性因子大部分也是有肝臟自身合成，如活性磷脂、膽汁酸、脂蛋白等等，才能順利完成脂質(zhì)代謝。因此，補(bǔ)充肝臟所需的活性因子是修復(fù)肝臟疾病的良好藥物，這也是大部分的肝病輔助藥物都是酶類、維生素類、氨基酸類等，飲食也是清淡蔬菜為主。
6 總結(jié)
霉菌毒素污染范圍廣泛，危害程度嚴(yán)重，是飼料工業(yè)和畜牧養(yǎng)殖業(yè)的重大問(wèn)題，如何有效防控和降解飼料和食品中的霉菌毒素將是畜牧業(yè)和食品工業(yè)亟待解決的科學(xué)難題。
The English version
 
Mycotoxins in animal feed, feed raw materials and widely exist in the human food, which is produced by mould in agricultural products series of toxic secondary metabolites with a broad range of chemical structure. Mycotoxin contamination animal husbandry economy loss, not only can cause fetal part have carcinogenic mycotoxin or birth defects, and can be in the animal residues in meat, eggs, milk, from the food chain enter human body, a serious threat to human health.
Mycotoxin contamination is serious in our country, feed animals feed of mycotoxin contamination can cause some diseases. Therefore, feed mycotoxins infection has become a feed industry and animal husbandry, the lack of eliminate mycotoxin, to guarantee the animal health, give full play to the animal production potential has great significance to reduce economic loss. Compared with other domestic animals, and the most extensive pig breeding management, thus the pig feed poisoning disease, the highest in all kinds of livestock disease probability, its biggest economic losses caused by.
1 mycotoxin produced and classification
For livestock and poultry breeding harm larger mycotoxin is mainly produced by the following four moulds belong to: aspergillus species (mainly secreted aflatoxin AFT, ochre and aspergillus toxin, etc.), penicillium (mainly secreted citrinin), sickle bacteria genera (mainly secrete toxins DON T 2 toxin, vomiting, corn gibberellic ketene, fu ma toxin, etc.), claviceps (mainly secreted ergot toxin).
So far there have been more than 300 kinds of mycotoxin were separated and identified, and the above several toxin is the current understanding of eight kinds of main toxins.
The mechanism of the 2 mycotoxins
Mycotoxin, from animal acute death, chronic death to slow growth and reproductive performance. Consume a certain amount of mycotoxin can weaken the immune system, reduce the animal's ability to fight infectious diseases, can make the animal viscera damage (such as liver, kidney, gastrointestinal tract, and reproductive organs, etc.), reproductive performance, and residues in animal products, cause a harm to human health.
Mycotoxin poisoning mainly animal feed into the feed contaminated by toxins, lack of nutrients in the diet, lack of protein, selenium and vitamins is one of the factors that cause the mycotoxin poisoning. Mycotoxins because most of the intermediate or end product toxicity and toxicity of mycotoxin, therefore to reduce or increase the exogenous compounds, metabolism of drugs affect the body's reaction to the toxin, such drugs for aflatoxin and ochre and aspergillus toxin effect is larger, and the single spore mold toxin is relatively small.
Usually mycotoxins in feed there is not a single but two or several exist, when different toxins exist at the same time, the mold toxin toxicity will likely additive effect, the additive effect, synergies, synergistic effect and the effect of the rivalry. Additive effect (Synergistic effects) refers to the combination between two kinds of mycotoxin is equal to the cumulative sum of action. The additive effect (Less than additive effects) refers to occur from a combination of two kinds of mycotoxin below the accumulation of both single function together. Synergistic effect (Synergistic effects) refers to two kinds of mycotoxin combination is higher than the accumulation of both single function together. Synergistic effect (Potentiate the effects) refers to a kind of mycotoxin on a tissue or organ does not produce toxic effects, but taken one after another mycotoxin, toxicity of the former to the latter. Rivalry effect (Antagonistic effects) is a mycotoxin interfere with another mycotoxin toxic effect, this kind of situation is rare.
2.1 aflatoxin
Aflatoxin (aflatoxin, referred to as AF) in the mycotoxin, considered most, the most harmful carcinogens, its heat resistance is strong, more than 80 ℃ to destroy, would produce fluorescence under ultraviolet light, is the product of huangshan mold and parasitic aspergillus, almost all of the animals is sensitive to AF, birds are the most sensitive. AF strong toxicity to young animals and fatality rate is high, and with a strong tolerance of adult animals. Yellow aspergillus (AF) can be divided into the aflatoxin B1, B2, G1, G2, M1, M2, of which the most damage, most toxic aflatoxin B1 (AFB1) is, for all the animals are the main influence tumor, immunosuppression, mutagenic and teratogenic effects of main target organ is the liver, is a hepatotoxin, can cause bleeding, hepatic steatosis, liver bile duct hyperplasia, etc., and can lead to the occurrence of cancer of the liver (yun-jie xu, etc., 2008; hu LAN, etc., 2001).
Yellow aspergillus toxin is the most serious harm in pig production of toxins, the harm of pigs are mainly
(1) is the most powerful immunosuppressant, when, after feed pigs feed contaminated with its first disturbance of immune system, increased predisposition to disease, drug treatment effect is poor.
(2) is clotting factor inhibitor, in injury time of bleeding and serous lower blotchy areas of hemorrhage, bleeding from the small intestine and colon, etc.
(3) infringe on the liver, cause liver function drops, hepatomegaly, bile secretion decline, resulting in a decline in feed utilization rate of protein and fat in (meng-yun li, etc., 2005). Research shows that the growth in pig diet containing aflatoxin mu 200-400 g/kg, pig growth and feed remuneration; Containing 400-800 mu g/kg, microscopic liver damage, cholangitis, hepatitis, immune inhibition; Containing 800-1200 mu g/kg, the growth, feed intake reduced, rough coat, jaundice, hypoalbuminemia. Containing 1200-2000 mu g/kg, characterized by jaundice, coagulopathy, spirit dull, anorexia, part of death (閆甫 etc., 2007).
2.2 ochre and aspergillus toxin
Ochratoxin (Ochratoxin, OCT) by certain strains of aspergillus and penicillium genus of A structure similar to that of toxic, secondary metabolites with Ochratoxin A (Ochratoxin A, OTA) toxicity strongest. Its toxic aflatoxin and kidney is the main target organ, is A kind of renal toxins, ochratoxin A for almost all animals have renal toxicity. Mankind, in particular, when low intake can cause reproductive performance. Studies have shown that the OTA single stomach to all mammals have renal toxicity, can cause renal atrophy or swelling, colors, animals going grey, cortical surface uneven, and the section visible cortical fibrous degeneration;
Microscopically visible renal tubular atrophy and interstitial fibrosis with renal glomerular hyaline degeneration, and small pipe ring die, etc., accompanied by reduced the volume of urine, blood urea nitrogen increased, cleared to amino hippuric acid reduced, frequent urination, urine protein and urine sugar increased renal impairment (li, 2009). To pig feeding with ochre and aspergillus toxin tests showed that the 1 mg/kg of feed for 3 months, can cause diarrhea, anorexia and dehydration, growth retardation, feed utilization rate is low, autopsy rare renal pale, hard, namely rubber kidney. In addition to the renal toxicity, OTA and liver toxicity, suppress the immune, teratogenic and carcinogenic. In terms of reproductive toxicity, for males, ochratoxin A can also make boar semen quality drops (Biroeta1, 2003).
2.3 the orange of penicillin
Orange penicillin (Citrinin) is penicillium and aspergillus certain strains of fungal poison, is a kind of renal toxins, it can lead to pigs, chickens, ducks and birds occurred almost all animals such as kidney disease, but the differences between acute toxicity in different varieties. For duck, half lethal dose is 57 mg/kg; Chicken is 95 mg/kg; The rabbit is 134 mg/kg. Orange penicillin has synergism with ochratoxin A, inhibits murine animal kidney RNA synthesis, wheat, oats, rye, or barley, corn, rice etc all orange penicillin (ren-rong liu, 2004).
2.4 single spore alkene toxins
Single-ended spore alkene toxins are produced by sickle species structure is the floorboard of the similar kind of compounds, species more than 148 species, including main representative: T - 2 toxin (T 2 toxin), two acetyl bodyguards grass sickle germ enol (DAS) and deoxidization snow enol. Major damage animal liver and kidney, and mostly belongs to the organization stimulating factor and inflammatory substances. T 2 toxin a major role in cell division of tissues and organs, such as thymus and bone marrow, liver, spleen, lymph nodes, gonads, and gastrointestinal mucosa, inhibit these organs protein and DNA synthesis, cell and nerve function damage.
T - 2 toxins or DAS can damage the digestive tract mucous membrane in the poultry, oral ulcer, general clinical symptoms of anorexia or loss, gastrointestinal inflammation, bleeding, vomiting, decreased immune function (Kubena, etc., 1994). Pigs to DON the most sensitive, the main cause pig anorexia, refus feeds, nausea and gastrointestinal injury. Many research shows that: the grain DON level up to 3 to 5 mg/kg, pigs greatly decreased appetite, and growth and production performance. When growing pig feed feed containing 14 mg/kg DON after 10 ~ 20 min can appear namely vomiting, abnormal phenomenon of anxiety and molar, DON to secrete nurse pig is more serious, the influence of amount of lactation sows decrease due to loss of appetite, leading to piglet growth speed is slow.
Another study showed that the content of DON in the 0 to 14 mg/kg trial, fodder in every increase 1 mg/kg DON, growth of fattening pigs feed intake by 6%, the poison content is more than 10 mg/kg, namely completely (Trenholm, etc., 1994). Feed intake reduce DON concentration increases linearly with the feed, the relationship. Single-ended spore alkene families of the other toxins or had no effect on production performance for ruminant animal health (Hou Ran however, etc., 2007). Study also shows that T - 2 toxin toxicity of different animals, we still have some differences between species, new or young animals than adult animals more sensitive to toxins, males than females are sensitive (huo seika, etc., 2008).
2.5 gibberellic ketene corn
Corn gibberellic ketene, polyketone synthesis by sickle mold of mammals have estrogen-like effect of a class of secondary metabolites. Appropriate conditions, all of the grain crops or feed products can be polluted by corn gibberellic ketene. Pig's most sensitive to corn gibberellic ketene, and most affected area is the reproductive system. Because corn red enzyme ketene have class estrogen effect, lower than l mg/kg in animal show the female character, boar will show testicular atrophy, nipple increase female characteristics.
For sows, the content is too high can cause ovulation, false pregnancy, fetal development, clinical characteristics and performance for vulva hyperemia, edema, breast swelling and nipple hypertrophy, serious when can cause the vagina and rectum (cheng-zhi guo, 2010). Corn ketene red enzyme can be associated with steroid synthesis enzyme reaction, affect the formation of steroids, interfere with the endocrine system, its long-term effect and toxicity of offspring effect needs further research.
2.6 v horse toxins
Fu ma cephalosporins is water-soluble metabolites produced by sickle species, is a kind of different and more hydrogen by 3 c structure similar to the double ester compounds composed of carboxylic acid. The strongest FB1 toxicity, it is found in recent years can damage the immune system, liver and kidney, reducing the mortality of animals productivity and even cause a mycotoxin. V horse rhzomorph associated with swine edema disease (PPE), lead to the change of pig lung epithelial cells of the blood capillary, respiratory disorder, heart function damage (Diaz, etc., 1994), and for the horse, fu ma rhzomorph liquefactive necrosis (ELEM) can cause brain white matter, brain cortex injury, ataxia, partial paralysis, listless and movement function weaken, sheep can also cause liver and kidney lesions (shao-kang wang, 2003
), and small doses of vomiting toxins and v horse toxins can activate many immune response, such as cytokines.
Combined with the toxicity mechanism of mycotoxin, can draw the mold toxin poisoning of animals mainly manifested in the immune system, gastrointestinal tract, liver, kidneys and reproductive system, etc. Table 3 shows different mycotoxin to the pig body levels of toxicity. Can be seen from the table mycotoxin on the immune function, reproductive capacity, pig feed intake and liver kidney has influence, and each kind of poison to the influence degree of each function is different.
3 mold toxin pollution for the feed
According to the United Nations food and agriculture organization (FAO), the world each year, about 25% of the grain under the influence of mycotoxins in different degrees, about 2% of the crops because of serious pollution and loss of nutritional value and economic value. Of Chinese 28 provinces and autonomous regions, 194 feed and raw material of corn, wheat bran, survey, DON, T 2 toxin and ZEN pollution rate are 50.0%, 18.1% and 50.0% respectively (meter into etc., 2007). Animal raw fish meal at the same time, a variety of mycotoxin contamination are also very common, mildew was feed in animal feed, toxin and its metabolites can be residues in animal products and its processing products, enters the body through the food chain, these highly pathogenic and carcinogenic toxin a serious threat to human health.
AoZhiGang (2008) found that a by-product of the material, especially corn by-products such as dry lees (DDGS) and corn protein powder of mycotoxin contamination is very serious, and a variety of feed ingredients and full price feed mycotoxins often exist at the same time, due to different toxins have synergy between, will add to the toxic effects of toxin and the severity of the poisoning symptoms. Zhang Cheng etc. (2009) for the first half of 2009 China feed and raw material sampling survey results show that in 90 samples, did not detect the sample only 8 of mycotoxin, accounting for 8.9% of the total number of samples; Only detect one kind of mycotoxin sample number is 7, 7.8% of the total number of samples; While detecting the number of samples containing more than 4 kinds of mycotoxin accounted for 67.8%. Huang Guangming etc. (2010) in 2008, 2009 and 2008 in China was analyzed from various provinces and cities in feed mills and farms feeds for customer acquisition of feed raw materials and samples, the results found that in most parts of our country, corn gibberellic ketene and vomiting toxins pollution situation is more serious, especially in 2009 and 2010.
4 pig mycotoxin poisoning prevention
There are synergies between various mycotoxins in feed, several kinds of mycotoxin synergy effect on animal health and production performance than any kind of mycotoxin separate function. Creates a more complex when pigs poisoning symptoms, especially when there is the presence of bacterial and viral factors are most important. Therefore, the variety of mycotoxin bacteria, viruses and mixed infection caused by swine poisoning diagnosis become more difficult. Pig mycotoxin poisoning diagnosis is difficult, after the poisoning of the treatment effect is not ideal, the pig should take effective measures to prevent in advance.
4.1 feed mildew proof measures
Feed mildew to start from the source, enhance the resistance to mold plant cultivation, choose mold resistant strains, strengthen field management. For the inevitable pollution, in the process of harvesting and storing should choose the right time to harvest, stored in temperature and humidity appropriate places. Need to strictly control the water content of feed ingredients. Water is decided to feed mildew can grow in one of the most main factor.
The ideal material should be no more than 12% of water content, water content > l5 % can cause mould to grow and multiply, feed water about % ~ 18% fungi reproduction for toxin-producing optimum conditions. Keep the equipment clean, not only control the pathogenic bacteria, and to control and reduce the growth of mold and the mold toxin in feed production equipment. When it is necessary to add fungicide, the economy and can get mould inhibitor to a large number of short chain fatty acids, such as formic acid, acetic acid and propionic acid, is currently the most commonly used mould inhibitor propionate, sodium propionate, calcium propionate, ammonium propionate and two ammonium propionate.
Propionic acid salt with the feed equipment, stability and corrosion in the advantages of long-term feed mildew role. Need to point out is, mould inhibitor can inhibit the growth of mold, and the existing mycotoxins in feed or feed raw materials.
4.2 mildew seedling of feed processing
Chemical methods
Alkali treatment, ozone treatment, ammonia treatment method and the methylamine and calcium hydroxide treatment may have certain effect. Ozone is a substance of double bond has preferential effect of strong oxidizer. Ozone can through chemical reaction in vitro degradation of AFB1, not much, AFB2 and AFG2, this has been confirmed by experiment.
He Zu equality with sodium bicarbonate, sodium hypochlorite, sodium hydroxide and sodium chloride to detoxification of penicillium acid, sodium bicarbonate, sodium hypochlorite and sodium hydroxide seedling has certain effect. Sodium sulfite and AF reaction of water-soluble products, so as to relieve toxicity of AF. Should pay attention to is this kind of method applies only to some sort of toxin, and not all can degrade, and residues of these chemicals in the feed problem cannot solve effectively and economically, so it's not very practical, and there is a danger.
The use of the adsorbent
Used to control mycotoxins in feed or food the most commonly used method is the use of mycotoxins adsorbent. Most mycotoxins adsorbent by lowering the mycotoxin mass concentration and reduce its an opportunity to enter the blood and target cells, thereby effectively prevent mycotoxins produce harm. Mainly includes the adsorbent inorganic and organic mycotoxins adsorbent two kinds big.
Various adsorption material, however, adsorption capacity and adsorption of different kind of toxin effects are each are not identical, while the use of a variety of adsorbent composite use whether can achieve the desired test the effect of the adsorption effect overlay should do to argue. Therefore, in actual production, feed, raw material of mildew poisoning situation is still severe. And adsorbent adsorption mycotoxin not only, also the adsorption of feed of small molecules, such as biotin, triggering the sow limb hoof disease.
Five pigs mycotoxin restoration of poisoning
Pig mycotoxin after poisoning, due to the violation is liver, kidney and other organs and suppression of the immune system, there is almost no good way to cure, the treatment of fatty liver disease and cirrhosis of the liver with humans is the same principle, the core is to reduce the financial burden on viscera and try to repair the function.
We in the liver repair, for example:
The liver is one of the most complex organ for animals, bear the protein, carbohydrate and lipid synthesis, decomposition and storage, especially in lipid metabolism, the liver synthetic lipoproteins, promotes lipid transport, also form the main fatty acid oxidation and ketone body place. Quality of normal liver fat, about 4%, mainly phospholipids. If the liver is not to fat out in time, fat accumulation in liver cells, namely the formation of fatty liver. Fat accumulated in the liver, can affect the liver cell function and damage of liver cells, the connective tissue hyperplasia, cause liver cirrhosis.
And various nutrients we need to rely on anabolic corresponding enzymes, vitamin, active substances, such as active factor to complete, and the most active factor is the liver has its synthesis, such as active phospholipids, bile acid, lipoprotein and so on, can smoothly complete the lipid metabolism. Supply active factor is required for the liver repair, therefore, good drug of liver disease, which is most of the auxiliary liver disease drug enzymes, vitamins, amino acids, food is bland vegetables give priority to.
6 summarizes
The wide range of mycotoxin contamination, damage is serious, is a major problem of feed industry and animal husbandry and aquaculture, how to effectively control and degradation of mycotoxins in feed and food will be scientific problem urgently to be solved in animal husbandry and food industry.
|
