Nihsen M E, Piper E L, West C P, Crawford R J, Denard T M, Johnson Z B, Roberts C A, Spiers D A, Rosenkrans C F
Department of Animal Science, University of Arkansas, Fayetteville 72701, USA.
J Anim Sci. 2004 Mar;82(3):878-83. doi: 10.2527/2004.823878x.
Cattle grazing tall fescue (Festuca arundinacea Schreb.) often develop fescue toxicosis. This condition is thought to be caused by ergot alkaloids produced by the endophyte Neotyphodium coenophialum. Endophytes from wild tall fescue plants, which do not produce ergot alkaloids, were transferred into the endophyte-free tall fescue germplasm, HiMag. The novel associations also lacked the ability to produce ergot alkaloids. Our objective was to determine whether cattle grazing these novel endophyte associations showed signs of fescue toxicosis. At the Fayetteville, Arkansas location, tester steers (n = 72) were assigned to one of four pasture treatments: endophyte-free HiMag tall fescue (HiMag-); 'Kentucky-31' tall fescue infected with its native, toxic endophyte (KY+); and two novel endophyte-infected tall fescue associations, HiMag4 and HiMag9. At the Mount Vernon, Missouri location, steers (n = 54) were used to test three of the four cultivars (HiMag9 was not tested). Ergot alkaloid concentrations in the forage of HiMag4 and HiMag9 were low or undetectable. Respiration rate, rectal temperature, ADG, and hair scores were measured during the grazing period. Blood was collected via jugular venipuncture and used for prolactin, aspartate aminotransferase, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cholesterol, triglyceride, and creatinine analysis. Weight gains by steers grazing HiMag4 and HiMag9 did not differ from those of steers grazing HiMag-, but were greater than gains (P < 0.05) by steers on the KY+ treatment. Steers grazing KY+ had higher (P < 0.05) respiration rates, rectal temperatures, and hair scores than did steers grazing novel endophyte and HiMag- pastures. Prolactin, ALP, cholesterol, LDH, and triglycerides all were suppressed (P < 0.05) in steers grazing KY+ compared with steers grazing novel endophyte and HiMag- pastures. Steers grazing the novel endophyte tall fescues did not suffer from the decreased weight gains and toxicities associated with fescue toxicosis, resulting in enhanced animal production.
放牧高羊茅（Festuca arundinacea Schreb.）的牛常常会患上高羊茅中毒症。这种病症被认为是由内生真菌Neotyphodium coenophialum产生的麦角生物碱引起的。将不产生麦角生物碱的野生高羊茅植物中的内生真菌转移到无内生真菌的高羊茅种质HiMag中。这些新的组合也缺乏产生麦角生物碱的能力。我们的目标是确定放牧这些新的内生真菌组合的牛是否表现出高羊茅中毒症的迹象。在阿肯色州费耶特维尔的试验场，将试验阉牛（n = 72）分配到四种牧场处理之一：无内生真菌的HiMag高羊茅（HiMag-）；感染了其原生有毒内生真菌的‘肯塔基31号’高羊茅（KY+）；以及两种新的感染内生真菌的高羊茅组合，HiMag4和HiMag9。在密苏里州弗农山的试验场，使用阉牛（n = 54）对四个品种中的三个进行测试（未测试HiMag9）。HiMag4和HiMag9的牧草中麦角生物碱浓度较低或无法检测到。在放牧期间测量呼吸频率、直肠温度、平均日增重（ADG）和毛发评分。通过颈静脉穿刺采集血液，用于催乳素、天冬氨酸转氨酶、碱性磷酸酶（ALP）、乳酸脱氢酶（LDH）、胆固醇、甘油三酯和肌酐分析。放牧HiMag4和HiMag9的阉牛的体重增加与放牧HiMag-的阉牛没有差异，但高于KY+处理组阉牛的增重（P < 0.05）。与放牧新内生真菌和HiMag-牧场的阉牛相比，放牧KY+的阉牛呼吸频率、直肠温度和毛发评分更高（P < 0.05）。与放牧新内生真菌和HiMag-牧场的阉牛相比，放牧KY+的阉牛的催乳素、ALP、胆固醇、LDH和甘油三酯均受到抑制（P < 0.05）。放牧新内生真菌高羊茅的阉牛没有遭受与高羊茅中毒症相关的体重增加减少和毒性问题，从而提高了动物产量。
