Aiken G E, Kirch B H, Strickland J R, Bush L P, Looper M L, Schrick F N
USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546, USA.
J Anim Sci. 2007 Sep;85(9):2337-45. doi: 10.2527/jas.2006-821. Epub 2007 May 25.
Color Doppler ultrasonography was used to compare blood flow characteristics in the caudal artery of heifers fed diets with endophyte (Neotyphodium coenophialum) infected (E+) or noninfected (E-) tall fescue seed. Eighteen crossbred (Angus x Brangus) heifers were assigned to 6 pens and were fed chopped alfalfa hay for 5 d and chopped alfalfa hay plus a concentrate that contained E-tall fescue seed for 9 d during an adjustment period. An 11-d experimental period followed, with animals in 3 pens fed chopped alfalfa hay plus a concentrate with E+ seed and those in the other 3 pens fed chopped hay plus concentrate with E E- seed. Color Doppler ultrasound measurements (caudal artery area, peak systolic velocity, end diastolic velocity, mean velocity, heart rate, stroke volume, and flow rate) and serum prolactin were monitored during the adjustment (baseline measures) and during the experimental period. Three baseline measures were collected on d 3, 5, and 6 during the adjustment period for comparison to post E+ seed exposure. Statistical analyses compared the proportionate differences between baseline and response at 4, 28, 52, 76, 100, 172, and 268 h from initial feeding of E+ seed. Serum prolactin concentrations on both diets were lower (P <0.001) than baseline beginning at 4 h from the start of the experimental period. However, trends in serum prolactin concentrations for heifers on the E- diet suggested ambient temperature was affecting these concentrations. Caudal artery area in E+ heifers had declined (P <0.10) from baseline by 4 h and was consistently lower (P <0.05) for the remainder of the period. Heart rates for E+ heifers were lower than the baseline rate from 4 (P <0.10) to 100 (P <0.001) h, but were similar (P >0.10) to the baseline for 172 and 268 h measures. Blood flow in E+ heifers was consistently lower than the baseline from 4 (P <0.05) to 172 (P <0.001) h, but was similar to the baseline at 268 h when heart rate was similar to the baseline rate. Caudal artery areas for the E- diet were similar to baseline areas except at 100 h when it was greater than baseline. Heart rates and flow rates for E- heifers did not differ (P >0.10) from baseline measures during the experimental period. Results indicated that onset of toxicosis was within 4 h of cattle exposure to E+ tall fescue and is related to vasoconstriction and reduction in heart rate.
采用彩色多普勒超声检查法，比较饲喂感染内生真菌（Neotyphodium coenophialum）的高羊茅种子（E+）或未感染内生真菌的高羊茅种子（E-）日粮的小母牛尾动脉血流特征。18头杂交（安格斯×婆罗格斯）小母牛被分配到6个围栏中，在适应期内，先饲喂切碎的苜蓿干草5天，然后饲喂切碎的苜蓿干草加含有E-高羊茅种子的精料9天。接下来是为期11天的试验期，3个围栏中的动物饲喂切碎的苜蓿干草加含有E+种子的精料，另外3个围栏中的动物饲喂切碎的干草加含有E-种子的精料。在适应期（基线测量）和试验期内，监测彩色多普勒超声测量指标（尾动脉面积、收缩期峰值速度、舒张末期速度、平均速度、心率、每搏输出量和流速）以及血清催乳素水平。在适应期的第3、5和6天收集三项基线测量指标，以便与接触E+种子后进行比较。统计分析比较了从开始饲喂E+种子起4、28、52、76、100、172和268小时时基线与反应之间的比例差异。从试验期开始4小时起，两种日粮的血清催乳素浓度均低于基线水平（P<0.001）。然而，E-日粮小母牛的血清催乳素浓度趋势表明环境温度正在影响这些浓度。E+小母牛的尾动脉面积在4小时时已从基线下降（P<0.10），并且在该时期的剩余时间内持续较低（P<0.05）。E+小母牛的心率从4小时（P<0.10）到100小时（P<0.001）低于基线心率，但在172和268小时测量时与基线相似（P>0.10）。E+小母牛的血流从4小时（P<0.05）到172小时（P<0.001）持续低于基线，但在268小时时与基线相似，此时心率与基线心率相似。E-日粮的尾动脉面积与基线面积相似，除了在100小时时大于基线。试验期内，E-小母牛的心率和流速与基线测量值无差异（P>0.10）。结果表明，牛接触E+高羊茅后4小时内出现中毒症状，且与血管收缩和心率降低有关。
