A metabonomic approach to identify biomarkers for bovine mycotoxicosis

真菌毒素是谷物、谷物、草和保存饲料中可能存在的真菌代谢物。若干风险因素增加了发生真菌毒素和真菌中毒（因摄入真菌毒素引起的动物疾病）的可能性，包括作物开花和收获前的高降雨量，因此2012年等潮湿夏季导致谷物中真菌毒素含量高。虽然对供人类食用的谷物中的真菌毒素浓度有强制性检测和立法限制，但对牲畜饲料没有法律要求。欧盟的指导方针建议谷物和全饲料中镰刀菌毒素——脱氧雪腐镰刀菌醇和玉米赤霉烯酮的最大限量。这些指南的制定是由于真菌毒素的主要研究领域集中在基于谷物的真菌毒素（主要是镰刀菌），使用单胃动物模型，如猪和家禽。然而，这并不包括广泛的真菌毒素，也不适用于反刍动物。最近的研究报告说，秸秆中的霉菌毒素浓度可能高于相关的谷物样品。青贮饲料（全作物（谷物和秸秆）、玉米和草）是乳牛和肉牛的主要饲料来源，是霉菌毒素的重要来源，对此的研究相对较少。该项目将通过反刍动物模型系统调查来自主要真菌属的更广泛真菌毒素来解决这一科学知识差距。由于瘤胃中具有弹性的微生物多样性，反刍动物比单一动物更能抵御真菌毒素的影响，但这种能力在应激时期（例如饮食改变或疾病）可能会受到损害。特别是，高产奶牛的饲粮（谷物和富含淀粉的谷物）导致标准瘤胃微生物群发生变化，由纤维分解（纤维降解）细菌组成，有利于更多淀粉降解生物，最终降低瘤胃pH值。此时，瘤胃解毒真菌毒素的能力大大降低。已经提出了不同物种的指导容忍水平，但尚不清楚这些指导标准的可靠性如何。英国最近的一项兽医调查显示，在以谷物为基础的口粮喂养的奶牛和肉牛群中，与不符合标准的好氧变质玉米和草青贮有关的真菌中毒发病率很高（10 - 80%）。真菌中毒的严重程度取决于霉菌毒素的种类、动物健康状况、生产阶段和食用剂量。有些类型直接损害器官（如肝脏、肾脏和瘤胃），而其他类型损害生殖或导致癌症。对身体的影响从性能下降到死亡不等。不同的真菌毒素可在瘤胃中相互作用，加剧这种影响，其中一些已知可抑制免疫功能。反刍动物真菌中毒的症状包括食欲不振、产奶量减少或体重增加不佳。由于缺乏特异性症状和牛酸中毒等其他代谢性疾病的重叠症状，早期兽医诊断真菌中毒是困难的。这一问题不会以动物疾病或生产损失告终，因为奶牛饲料中的霉菌毒素可能导致其代谢物出现在乳制品中，从而对人类健康，特别是对婴儿构成风险。因此，需要一种反刍动物真菌中毒的快速早期检测方法。该项目将从患有真菌中毒的动物的尿液、唾液和血浆中提取代谢物，作为该疾病的生物标志物。这些信息在未来更多的应用项目中可以发展成为兽医的快速诊断工具。作为一个工业合作伙伴奖励项目，与动物饲料、生物化学和制药产品相关的主要行业成员已经签署协议，将该项目的基础科学发展为工业发展，以实现研究的最大影响。

Mycotoxins are fungal metabolites that can be present on grain, cereals, grass and conserved forage. Several risk factors increase the likelihood of mycotoxins and mycotoxicosis (disease in animals caused by mycotoxin ingestion), including high rainfall at crop flowering and during pre-harvest, hence wet summers such as 2012 result in high mycotoxin levels in grain. Although there is compulsory testing and legislative limits to concentrations of mycotoxins in grain destined for human consumption, there are no legal requirements for livestock feeds. The EU guidelines suggest maximum limits for Fusarium mycotoxins - Deoxynivalenol, and Zearalenone - for grains and complete feeds. These guidelines have been produced as a result of the major research area in mycotoxins concentrating on grain based mycotoxins (mainly Fusarium) using monogastric animal models e.g. pigs and poultry. However, this does not cover the broad spectrum of mycotoxins nor is it applicable to ruminants. Recent research has reported higher concentrations of mycotoxins can occur in straw than the associated grain samples. Silage (whole crop (grain and straw), maize and grass) the main forage source for dairy and beef cattle represents a significant source of mycotoxins, for which there is comparatively little research. This project will address this gap in scientific knowledge by investigating a broader spectrum of mycotoxins from the main fungal genera with a ruminant model system.Due to the resilient microorganism diversity in the rumen, ruminants can withstand the effects of mycotoxins better than monogastrics, but this capacity may be compromised during times of stress (e.g. diet change or disease). In particular high production dairy cows are offered diets (cereals and grains rich in starch) which result in a change in the standard rumen microflora populated by fibrolytic (fibre degrading) bacteria in favour of more starch degrading organism which ultimately reduces the pH of the rumen. At this point the ability of the rumen to detoxify mycotoxins is substantially reduced. Guideline tolerance levels for different species have been proposed, but it is unknown how reliable these guidelines are. A recent veterinary survey in the UK showed a high incidence (10 - 80%) of mycotoxicosis in dairy and beef herds associated with sub-standard aerobically spoiled maize and grass silage when fed with cereal based rations. The severity of mycotoxicosis depends on the mycotoxin type, animal health, stage of production and dose eaten. Some types damage organs directly (e.g. liver, kidney and rumen), whilst others impair reproduction or cause cancer. Physical effects range from performance loss to mortality. Different mycotoxins can interact in the rumen to exacerbate the effect and some are known to suppress immune function. Signs of mycotoxicosis in ruminant animals include loss of appetite, reduced milk yield or poor weight gain. Early veterinary diagnosis of mycotoxicosis is difficult due to a lack of specific symptoms and overlapping symptoms of other metabolic diseases such as acidosis in cattle. The problem does not end in animal disease or production losses as mycotoxins in the feed of dairy animals can lead to their metabolites appearing in dairy products, which pose a risk in human health, particularly for infants. A rapid early detection method of mycotoxicosis for ruminants is therefore required.This project will produce a metabolite profile from urine, saliva and plasma of animals suffering mycotoxicosis to be used as biomarkers of the disease. This information in future more applied projects could be developed into a rapid diagnosis tool for veterinarians. As an industrial partner award project key industry members associated with animal feed, biochemistry and pharmaceutical products have already signed up to develop the basic science from this project into industrial development for maximum impact of the research.