Geeslin Meagan D, Richeson John T, Hernandez Gifford Jennifer A, Soto-Navarro Sergio A, Burdick Sanchez Nicole C, Samuelson Kendall L
Department of Agricultural Sciences, West Texas A&M University, Canyon, TX, USA.
Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM, USA.
Transl Anim Sci. 2024 Sep 30;8:txae141. doi: 10.1093/tas/txae141. eCollection 2024.
The objective of this study was to evaluate the impacts of stress challenge duration on metabolic, hematologic, and rumen fermentation parameters of beef steers. Thirty steers (416 ± 19 kg) were used in a randomized complete block design with 2 blocks and 3 treatments. Treatments were intravenous injection of (1) saline at 0, 24, 48, and 72 h ( = 10; control); (2) corticotropin-releasing hormone (CRH) and vasopressin (VP) at 0 h and saline at 24, 48, and 72 h ( = 10; acute); or (3) CRH and VP at 0, 24, 48, and 72 h ( = 10; chronic). Serum samples were collected at various time points for analysis of serum chemistry and nonesterified fatty acids (NEFA). Whole blood was collected for analysis of complete blood count, and ruminal fluid was collected via oral lavage to evaluate volatile fatty acid (VFA) composition. Serum cortisol was greater (treatment × hour; ≤ 0.01) for cattle receiving acute and chronic than control at 1 h ( < 0.01) and greater for chronic than acute and control at 25, 26, 49, 50, 73, and 74 h ( < 0.01). Similarly, there was a treatment × hour interaction ( < 0.01) for serum glucose concentrations such that cattle receiving acute and chronic had greater glucose at 1 h than control ( < 0.01), and cattle receiving chronic had greater glucose at 25, 49, 73, and 74 h than acute and control ( ≤ 0.04). Serum insulin concentrations were greater (treatment × hour < 0.01) in chronic and acute than control at 1 h (< 0.01) and greater for chronic compared to acute and control at 25, 49, and 73 h ( ≤ 0.01). Serum NEFA tended ( = 0.09) to be greater in stressed cattle compared to control. There was a treatment × hour interaction ( = 0.003) for total white blood cell count such that chronic had greater concentration than control at 72 h ( < 0.01). Conversely, monocyte concentration was less (treatment × hour interaction < 0.01) for chronic than acute and control at 144 h ( < 0.01) and eosinophil concentration was greater (treatment × hour interaction = 0.02) for chronic than control steers at 48 h (= 0.02) and greater for chronic than acute at 72 and 144 h ( ≤ 0.03). Minimal differences were observed in VFA concentrations with the exception of acetate (treatment × hour interaction = 0.05). These results demonstrate that administration of CRH and VP affects complete blood count and serum chemistry, and longer duration of treatment exposure prolongs the physiological responses to a stress challenge.
本研究的目的是评估应激挑战持续时间对肉牛代谢、血液学和瘤胃发酵参数的影响。采用随机完全区组设计，将30头肉牛（416±19千克）分为2个区组和3种处理。处理方式为静脉注射：（1）在0、24、48和72小时注射生理盐水（n = 10；对照组）；（2）在0小时注射促肾上腺皮质激素释放激素（CRH）和血管加压素（VP），在24、48和72小时注射生理盐水（n = 10；急性组）；或（3）在0、24、48和72小时注射CRH和VP（n = 10；慢性组）。在不同时间点采集血清样本，用于分析血清生化指标和非酯化脂肪酸（NEFA）。采集全血用于分析全血细胞计数，并通过口腔灌洗采集瘤胃液以评估挥发性脂肪酸（VFA）组成。在1小时时，急性组和慢性组肉牛的血清皮质醇浓度高于对照组（处理×时间；P≤0.01）（P<0.01），在25、26、49、50、73和74小时时，慢性组高于急性组和对照组（P<0.01）。同样，血清葡萄糖浓度存在处理×时间交互作用（P<0.01），急性组和慢性组肉牛在1小时时的葡萄糖浓度高于对照组（P<0.01），慢性组肉牛在25、49、73和74小时时的葡萄糖浓度高于急性组和对照组（P≤0.04）。慢性组和急性组在1小时时的血清胰岛素浓度高于对照组（处理×时间P<0.01）（P<0.01），在25、49和73小时时，慢性组高于急性组和对照组（P≤0.01）。与对照组相比，应激肉牛的血清NEFA有升高趋势（P = 0.09）。总白细胞计数存在处理×时间交互作用（P = 0.003），慢性组在72小时时的浓度高于对照组（P<0.01）。相反，在144小时时，慢性组的单核细胞浓度低于急性组和对照组（处理×时间交互作用P<0.01）（P<0.01），在48小时时，慢性组的嗜酸性粒细胞浓度高于对照组肉牛（处理×时间交互作用P = 0.02）（P = 0.02），在72和144小时时，慢性组高于急性组（P≤0.03）。除乙酸盐外，VFA浓度差异极小（处理×时间交互作用P = 0.05）。这些结果表明，CRH和VP的给药会影响全血细胞计数和血清生化指标，且治疗暴露时间越长，对应激挑战的生理反应持续时间越长。
