Department of Animal and Food Sciences, University of Kentucky, Lexington 40546, USA.
J Anim Sci. 2013 Aug;91(8):3881-8. doi: 10.2527/jas.2013-6232.
This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348 ± 13 kg) were BW-matched into pairs and used in a 2 period crossover design experiment. Each period consisted of 2 temperature segments, one each at 22 and 30°C. During each period, 1 steer per pair was ruminally dosed twice daily with 0.5 kg of ground endophyte-infected fescue seed (E+) and the other with ground endophyte-free fescue seed (E-) for 7 d. Steers on E- treatment were pair-fed to E+ steers offered alfalfa cubes at 1.5 × NEm. On d 8 of each segment, steers were moved to individual metabolism stalls fitted with indirect calorimetry head boxes. Ruminal contents were removed, weighed, and subsampled for DM determinations. The reticulorumen was washed and filled with a buffer (NaCl = 96; NaHCO3 = 24; KHCO3 = 30; K2HPO4 = 2; CaCl2 = 1.5; MgCl2 = 1.5 mmol·kg buffer(-1)) that was gassed with a 75% N2 and 25% CO2 mixture before rumen incubation. During buffer incubation, an E+ or E- fescue seed extract was added at 12 h intervals to maintain treatment presentation to the animal. After a 12-h wait, heart rate, O2 consumption, CO2 production, and urinary output were recorded for 16 h. There was no difference (P = 0.931) in DMI/kg(0.75) between endophyte treatments by design; however, intake decreased (P = 0.004) at 30°C. Increased temperature had no effect (P > 0.10) on other measurements and there were no significant interactions (P > 0.11) of temperature and endophyte treatment. Heart rate was unaffected by fescue treatment or environmental temperature. Percent DM of ruminal contents as well as total rumen DM/kg(0.75) was increased (P < 0.0001) in E+ steers. Respiratory quotient was elevated (P = 0.02) in E+ steers. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) during E+ treatment. Calculated FHP (kcal/kg BW(0.75)) was also less (P = 0.006) in steers receiving E+ treatment. These data suggest that consumption of endophyte-infected tall fescue by cattle results in a reduction in basal metabolic rate.
本研究旨在探讨雀麦纤维中毒过程中空腹产热（FHP）的变化。6 头瘤胃内置有套管的荷斯坦奶牛（BW=348±13kg）按 BW 配对分为两组，并进行 2 期交叉设计实验。每个时期由 2 个温度段组成，每个温度段各有 1 个 22°C 和 30°C。在每个时期，每对中的 1 头奶牛每天通过瘤胃两次投喂 0.5kg 受内生真菌感染的雀麦种子（E+），另一头投喂无内生真菌的雀麦种子（E-），持续 7d。E-处理的奶牛按 E+奶牛的需要进行等量喂养，提供苜蓿立方体，喂养量为 1.5×NEm。每个温度段的第 8d，奶牛被转移到装有间接测热顶箱的单独代谢厩舍中。取出瘤胃液，称重，并取部分样品进行 DM 测定。反刍窦冲洗并用缓冲液（NaCl=96；NaHCO3=24；KHCO3=30；K2HPO4=2；CaCl2=1.5；MgCl2=1.5mmol·kg-1缓冲液）填充，在瘤胃孵育前用 75%N2 和 25%CO2 的混合物对缓冲液进行充气。在缓冲液孵育过程中，每隔 12h 添加 E+或 E-雀麦种子提取物，以保持对动物的治疗呈现。等待 12h 后，记录 16h 的心率、O2 消耗、CO2 产生和尿排出量。设计上，内生真菌处理对 DMI/kg(0.75)没有差异（P=0.931）；然而，在 30°C 时，摄入量下降（P=0.004）。温度升高对其他测量值没有影响（P＞0.10），温度和内生真菌处理之间也没有显著的相互作用（P＞0.11）。雀麦处理或环境温度对心率没有影响。E+奶牛的瘤胃内容物 DM%以及总瘤胃 DM/kg(0.75)均增加（P＜0.0001）。E+奶牛的呼吸商升高（P=0.02）。E+处理时，O2 消耗减少（P=0.04），CO2 产生趋于减少（P=0.07）。计算得出的基础代谢率（kcal/kgBW(0.75)）也较低（P=0.006）。这些数据表明，牛摄入受内生真菌感染的高羊茅会导致基础代谢率降低。
