Foote A P, Kristensen N B, Klotz J L, Kim D H, Koontz A F, McLeod K R, Bush L P, Schrick F N, Harmon D L
Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
J Anim Sci. 2013 Nov;91(11):5366-78. doi: 10.2527/jas.2013-6517. Epub 2013 Aug 29.
An experiment was conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen. Steers (n=8) were pair-fed alfalfa cubes and received ground endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum; E+) seed (0.015 mg ergovaline·kg BW(-1)·d(-1)) or endophyte-free tall fescue (E-) seed via the rumen cannula 2x daily for 7 d at thermoneutral (TN; 22°C) and heat stress (HS; 32°C) conditions. On d 8, the rumen was emptied and rinsed. A buffer containing VFA was incubated in the following sequence: control (CON), 15 μg ergovaline·kg BW(-1) (1×EXT) from a tall fescue seed extract, and 45 μg ergovaline·kg BW(-1) (3×EXT). For each buffer treatment there were two 30-min incubations: a 30-min incubation of a treatment buffer with no sampling followed by an incubation of an identical sampling buffer with the addition of Cr-EDTA and deuterium oxide (D2O). Epithelial blood flow was calculated as ruminal clearance of D2O corrected for influx of physiological water and liquid outflow. Feed intake decreased with dosing E+ seed at HS but not at thermoneutral conditions (TN; P<0.02). Dosing E+ seed decreased serum prolactin (P<0.005) at TN. At HS, prolactin decreased in both groups over the 8-d experiment (P<0.0001), but there was no difference in E+ and E- steers (P=0.33). There was a seed treatment×buffer treatment interaction at TN (P=0.038), indicating that E+ seed treatment decreased reticuloruminal epithelial blood flow at TN during the CON incubation, but the two groups of steers were not different during 1×EXT and 3×EXT (P>0.05). Inclusion of the extract in the buffer caused at least a 50% reduction in epithelial blood flow at TN (P=0.004), but there was no difference between 1×EXT and 3×EXT. There was a seed × buffer treatment interaction at HS (P=0.005), indicating that the reduction of blood flow induced by incubating the extract was larger for steers receiving E- seed than E+ seed. Volatile fatty acid flux was reduced during the 1×EXT and 3×EXT treatments (P<0.01). An additional experiment was conducted to determine the effect of time on blood flow and VFA flux because buffer sequence could not be randomized. Time either increased (P=0.05) or did not affect blood flow (P=0.18) or VFA flux (P>0.80), indicating that observed differences are due to the presence of ergot alkaloids in the rumen. A decrease in VFA absorption could contribute to the signs of fescue toxicosis including depressed growth and performance.
进行了一项实验，以确定麦角生物碱是否会影响瘤胃吸收表面的血流。选用8头阉牛，成对饲养，喂给苜蓿块，并通过瘤胃瘘管每天2次给予内生真菌感染（Neotyphodium coenophialum）的高羊茅（Lolium arundinaceum；E+）种子（0.015毫克麦角缬氨酸·千克体重-1·天-1）或无内生真菌的高羊茅（E-）种子，持续7天，实验在热中性（TN；22°C）和热应激（HS；32°C）条件下进行。在第8天，排空并冲洗瘤胃。含有挥发性脂肪酸（VFA）的缓冲液按以下顺序进行孵育：对照（CON）、来自高羊茅种子提取物的15微克麦角缬氨酸·千克体重-1（1×EXT）和45微克麦角缬氨酸·千克体重-1（3×EXT）。对于每种缓冲液处理，进行两次30分钟的孵育：一次是用处理缓冲液孵育30分钟，期间不取样，随后是用添加了铬-乙二胺四乙酸（Cr-EDTA）和氧化氘（D2O）的相同取样缓冲液进行孵育。上皮血流通过校正生理水流入和液体流出的D2O瘤胃清除率来计算。在热应激条件下，给予E+种子时采食量下降，但在热中性条件下（TN）未下降（P<0.02）。在热中性条件下，给予E+种子会降低血清催乳素水平（P<0.005）。在热应激条件下，在8天的实验中两组的催乳素水平均下降（P<0.0001），但E+和E-阉牛之间无差异（P=0.33）。在热中性条件下存在种子处理×缓冲液处理的交互作用（P=0.038），表明在对照孵育期间，E+种子处理会降低热中性条件下瘤网胃上皮血流，但在1×EXT和3×EXT期间两组阉牛无差异（P>0.05）。在缓冲液中加入提取物会使热中性条件下上皮血流至少降低50%（P=0.004），但1×EXT和3×EXT之间无差异。在热应激条件下存在种子×缓冲液处理的交互作用（P=0.005），表明对于接受E-种子的阉牛，孵育提取物诱导的血流减少幅度大于接受E+种子的阉牛。在1×EXT和3×EXT处理期间，挥发性脂肪酸通量降低（P<0.01）。由于缓冲液顺序无法随机化，因此进行了另一项实验以确定时间对血流和挥发性脂肪酸通量的影响。时间要么增加（P=0.05），要么不影响血流（P=0.18）或挥发性脂肪酸通量（P>0.80），这表明观察到的差异是由于瘤胃中存在麦角生物碱。挥发性脂肪酸吸收减少可能导致高羊茅中毒的症状，包括生长和生产性能下降。
