Abstract：
The increasing spread of ragworts is observed with concern. Ragworts like tansy ragwort (Jacobaea vulgaris Gaertn.) or marsh ragwort (J. aquatica) contain pyrrolizidine alkaloids (PA) which may induce hepatotoxic effects. Grazing animals usually avoid ragworts if their pasture management is appropriate. Preserved feed prepared from ragworts contaminated meadows may, however, lead to a significant exposure to PA. Previous studies on toxicity of PA for dairy cows revealed inconsistent results due to feeding ragwort plant material which was associated with heterogeneous PA exposure and thus failed to conclusively deduce critical PA doses. Therefore, the aim of the present study was to expose dairy cows (n = 4 per group) in a short-term scenario for 28 days with increasing PA doses (PA1: 0.47 mg PA/kg body weight (BW)/day (d); PA2: 0.95 mg PA/kg BW/d; PA3: 1.91 mg PA/kg BW/d) via oral administration by gavage of a defined PA-extract. While group PA3 was dosed with the PA-extract alone, groups PA2 and PA1 received PA-extracts blended in similar volumes with molasses to provide comparable amounts of sugar. Additionally, two control groups were treated either with water (CONWater) or with molasses (CONMolasses) to assess the effects of sugar without PA interference. While clinical traits including dry matter intake, milking performance, rectal body temperature, ruminal activity and body condition score (BCS) were not influenced by PA exposure, activities of enzymes indicative for liver damages, such as gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH), increased significantly over time at an exposure of 1.91 mg total PA/kg BW/d.
摘要：
令人担忧的是，观察到牧草的传播增加。像艾菊树草（JacobaeavulgarisGaertn。)或沼泽参草(J.aquatica）含有吡咯烷基生物碱（PA），可诱导肝毒性作用。如果放牧动物的牧场管理适当，通常会避免使用牧草。从受污染的牧草草甸制备的保藏饲料可能，然而,导致显著暴露于PA。先前关于PA对奶牛的毒性的研究显示，由于饲喂与异质PA暴露有关的牧草植物材料，因此未能最终推断临界PA剂量，因此结果不一致。因此,本研究的目的是在短期情况下暴露奶牛(每组n=4)28天,同时增加PA剂量(PA1:0.47mgPA/kg体重(BW)/天(d);PA2:0.95mgPA/kgBW/d;PA3:1.91mgPA/kgBW/d),通过灌胃给药确定的PA提取物.虽然PA3组单独服用PA提取物，PA2和PA1组接受与糖蜜混合的相似体积的PA提取物以提供相当量的糖。此外,两个对照组用水(CONWater)或糖蜜(CONMolmaes)处理,以评估无PA干扰的糖的效果。虽然临床特征包括干物质摄入量，挤奶性能,直肠体温,瘤胃活动和身体状况评分（BCS）不受PA暴露的影响，指示肝损伤的酶活性，如γ-谷氨酰转移酶（GGT），天冬氨酸转氨酶（AST）和谷氨酸脱氢酶（GLDH），在暴露于1.91mg总PA/kgBW/d时，随着时间的推移显着增加。
