Department of Animal Science, North Carolina State University, Raleigh, NC.
J Anim Sci. 2019 Sep 3;97(9):3776-3785. doi: 10.1093/jas/skz249.
Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue and is detrimental to growth and performance. Recent research has shown that supplementing protein has the potential to enhance growth performance in weaned steers. Therefore, the objective of this study was to evaluate the effect of supplemental CP on physiological parameters in stocker steers experiencing fescue toxicosis. Thirty-six weaned Angus steers (6 mo of age) stratified by weight (196.1 ± 3.6 kg) were assigned to a 2 × 2 factorial arrangement for 56 d: endophyte-free (EF) seed and 14% CP (EF-14; n = 9), EF seed and 18% CP (EF-18; n = 9), endophyte-infected (EI) seed and 14% CP (EI-14; n = 9), and EI seed and 18% CP (EI-18; n = 9). Steer growth and hemodynamic responses were collected weekly during ergot alkaloid exposure. On day 14 of the trial, iButton temperature data loggers were subcutaneously inserted in the lateral neck region to record hourly body temperature for 42 d. Data were analyzed using PROC MIXED of SAS with repeated measures. No differences were observed in DMI, BW, ADG, F:G, or BCS during the treatment period (P > 0.05). Hair shedding scores, rectal temperatures, surface temperatures, and respiration rates were greater in EI steers compared to EF steers regardless of supplemental CP (P < 0.05). However, subcutaneous body temperature was greater in EI-14 steers (37.94 °C) compared to other steer groups (37.60, 37.68, 37.72 ± 0.04 °C for EF-14, EF-18, and EI-18, respectively; P < 0.05). Prolactin concentrations tended to be greater in EF steers when compared to EI steers (P = 0.07). Heart rate and hematocrit were reduced for EI-18 steers compared to other steer groups (P < 0.05). Caudal artery diameter was reduced in EI-18 steers compared to EI-14 steers (2.60 vs. 2.75 ± 0.05 mm, respectively; P < 0.05) and caudal vein diameter was reduced in EI-18 steers (3.20 mm) compared to all other steer groups (3.36, 3.39, 3.50 mm for EF-14, EF-18, and EI-14, respectively; P < 0.05). However, there was no difference observed in systolic or diastolic blood pressure during the treatment period (P > 0.05). Based on the data, exposure to low to moderate levels of ergot alkaloids during the stocker phase had a negative impact on hemodynamic responses and supplemental CP had minimal impact to alleviate symptoms. Therefore, feeding additional protein above established requirements is not expected to help alleviate fescue toxicosis.
赤霉烯酮中毒是一种常见于采食内生真菌感染高羊茅的牛的多方面综合征，对生长和性能有不利影响。最近的研究表明，补充蛋白质有可能提高断奶牛的生长性能。因此，本研究的目的是评估补充 CP 对内毒素中毒牛生理参数的影响。36 头断奶安格斯牛（6 月龄）按体重（196.1±3.6kg）分层，采用 2×2 因子设计，持续 56d：无内生真菌（EF）种子和 14%CP（EF-14；n=9）、EF 种子和 18%CP（EF-18；n=9）、内生真菌感染（EI）种子和 14%CP（EI-14；n=9）和 EI 种子和 18%CP（EI-18；n=9）。在麦角生物碱暴露期间，每周收集牛的生长和血液动力学反应数据。试验第 14 天，将 iButton 温度数据记录器皮下插入颈侧区，记录 42d 内每小时的体温。数据采用 SAS 的 PROC MIXED 进行重复测量分析。在处理期内，DMI、BW、ADG、F：G 或 BCS 没有差异（P>0.05）。无论补充 CP 如何，EI 牛的毛脱落评分、直肠温度、表面温度和呼吸率均高于 EF 牛（P<0.05）。然而，与其他牛群相比，EI-14 牛的皮下体温更高（37.94°C）（EF-14、EF-18 和 EI-18 分别为 37.60、37.68 和 37.72±0.04°C；P<0.05）。与 EI 牛相比，EF 牛的催乳素浓度趋于更高（P=0.07）。与其他牛群相比，EI-18 牛的心率和红细胞压积降低（P<0.05）。与 EI-14 牛相比，EI-18 牛的尾动脉直径减小（2.60 对 2.75±0.05mm；P<0.05），尾静脉直径减小（EI-18 牛为 3.20mm）（与其他牛群相比，EF-14、EF-18 和 EI-14 分别为 3.36、3.39 和 3.50mm；P<0.05）。然而，在处理期间，收缩压或舒张压没有差异（P>0.05）。根据数据，在育肥期接触低至中等水平的麦角生物碱对内毒素中毒的血液动力学反应有负面影响，而补充 CP 对内毒素中毒的影响最小，无法缓解症状。因此，预计额外补充高于既定需求的蛋白质无助于缓解赤霉烯酮中毒。
