Stress during the transition of beef steers from ranch to feedlot may depend on steer source and preconditioning. The interplay between physiological and behavioral patterns of preconditioned (PC) and auction-derived (AD) steers, particularly after commingling, is poorly understood. Our objective was to evaluate whether hair cortisol (HC) concentrations were related to the health and performance of PC and AD steers and study behavioral activities after commingling over 6 wk in a feedlot. Steers, sourced either from ranch (PC, n = 250) or local auction (AD, n = 250), were assigned into 1 of 5 pens, 100% PC (100PC); 75% PC 25% AD (75PC); 50% PC 50% AD (50PC); 25% PC 75% AD (25PC), and 100% AD (0PC), each pen containing 100 steers. Pen was the experimental unit and individual steers were the observational unit where physiological and behavioral changes were measured. The study subsampled 225 steers (PC = 113 and AD = 112) which were equipped with CowManager ear tags to record behaviors. On day 40, hair samples from each steer were collected by clipping hair close to the skin. Data were analyzed using multiple linear, logistic regression, or multilevel negative binomial regression models depending on the outcomes. There was no difference in HC concentrations (day 40) between PC and AD steers (P = 0.66), and no association with Bovine Respiratory Disease (BRD)-related morbidity (P = 0.08) or average daily gain (ADG) (P = 0.44). After adjusting for source and commingling effects, HC concentrations did not affect time spent eating (P = 0.83), ruminating (P = 0.20), active (P = 0.89), or non-active (P = 0.32). PC steers spent more time eating and ruminating over weeks 1 to 4 (P < 0.01) and weeks 1 to 3, respectively (P < 0.05), and more time being active over weeks 1 and 2 compared to AD steers (P < 0.001), but less time being non-active than AD steers on weeks 1 to 3 (P < 0.001). Steers in 100PC and 50PC pens spent more time eating than steers in 0PC (P < 0.001), whereas steers in 25PC spent less time eating than steers in 0PC (P < 0.001). Steers in 0PC spent the most time being not active (P < 0.01). In conclusion, preconditioned steers spent more time eating, ruminating, and being active and less time being not active over the first 3 wk in the feedlot, regardless of commingling. The HC concentrations did not identify potentially lower stress related to ranch transfer and were neither associated with BRD-related morbidity nor ADG.

中文翻译：

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行为活动模式而不是毛发皮质醇浓度解释了阉牛在饲养场前 6 周的过渡相关应激


肉牛从牧场过渡到饲养场期间的压力可能取决于阉牛来源和预处理。人们对预处理 （PC） 和拍卖衍生 （AD） 阉牛的生理和行为模式之间的相互作用知之甚少，尤其是在混合之后。我们的目标是评估毛发皮质醇 （HC） 浓度是否与 PC 和 AD 阉牛的健康和性能有关，并研究在饲养场混合超过 6 周后的行为活动。来自牧场（PC，n = 250）或当地拍卖（AD，n = 250）的公牛被分配到 5 个围栏中的 1 个，100% PC （100PC）;75% PC 25% AD （75PC）;50% PC 50% AD （50PC）;25% PC、75% AD （25PC） 和 100% AD （0PC），每个围栏包含 100 头公牛。笔是实验单位，个体公牛是测量生理和行为变化的观察单位。该研究对 225 头公牛（PC = 113 和 AD = 112）进行了二次抽样，这些公牛配备了 CowManager 耳标来记录行为。在第 40 天，通过将靠近皮肤的头发剪下来收集每头公牛的毛发样本。根据结果，使用多元线性、 logistic 回归或多级负二项式回归模型分析数据。PC 和 AD 阉牛之间的 HC 浓度 （第 40 天） 没有差异 （P = 0.66），并且与牛呼吸疾病 （BRD） 相关发病率 （P = 0.08） 或平均日增重 （ADG） 无关 （P = 0.44）。在调整了来源和混合效应后，HC 浓度不会影响进食时间 （P = 0.83）、反刍时间 （P = 0.20）、活跃时间 （P = 0.89） 或非活跃时间 （P = 0.32）。PC 阉牛在第 1 至 4 周 （P < 0.01） 和第 1 至 3 周分别花费更多时间进食和反刍 （P < 0.05），与AD阉牛相比，第1周和第2周的活跃时间更多（P < 0.001），但在第1至第3周的非活动时间比AD阉牛少（P < 0.001）。100PC 和 50PC 围栏中的犊牛比 0PC 中的犊牛吃奶的时间更多 （P < 0.001），而 25PC 中的犊牛比 0PC 中的犊牛花更少的时间进食 （P < 0.001）。0PC 的公牛不活跃的时间最长 （P < 0.01）。总之，无论混合如何，经过预处理的阉牛在饲养场的前 3 周内花更多的时间进食、反刍和活跃，而不花时间不活跃的时间更少。HC 浓度未确定与牧场转移相关的潜在较低压力，并且与 BRD 相关发病率或 ADG 无关。