Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae236.
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.
牛只从牧场转移到饲养场时的压力可能取决于牛的来源和预处理情况。预处理（PC）和拍卖来源（AD）牛的生理和行为模式之间的相互作用，特别是在混合之后，了解甚少。我们的目的是评估头发皮质醇（HC）浓度是否与 PC 和 AD 牛的健康和性能有关，并在饲养场中混合 6 周后研究其行为活动。牛只来自牧场（PC，n=250）或当地拍卖（AD，n=250），被分配到 5 个围栏中的 1 个，每个围栏包含 100 头牛：100% PC（100PC）；75% PC 25% AD（75PC）；50% PC 50% AD（50PC）；25% PC 75% AD（25PC）和 100% AD（0PC）。围栏是实验单位，个体牛是观察单位，在那里测量生理和行为变化。研究对 225 头牛（PC=113 头，AD=112 头）进行了亚采样，这些牛配备了 CowManager 耳标来记录行为。在第 40 天，从每头牛身上剪下靠近皮肤的毛发进行取样。根据结果，使用多元线性、逻辑回归或多水平负二项式回归模型进行数据分析。PC 和 AD 牛的 HC 浓度（第 40 天）之间没有差异（P=0.66），与牛呼吸道疾病（BRD）相关发病率（P=0.08）或平均日增重（ADG）（P=0.44）也没有关联。在调整来源和混合效应后，HC 浓度不会影响采食时间（P=0.83）、反刍时间（P=0.20）、活动时间（P=0.89）或非活动时间（P=0.32）。PC 牛在第 1 周到第 4 周（P<0.01）和第 1 周到第 3 周（P<0.05）分别花费更多时间采食和反刍，与 AD 牛相比，在第 1 周到第 2 周花费更多时间活动（P<0.001），但在第 1 周到第 3 周非活动时间比 AD 牛少（P<0.001）。100PC 和 50PC 围栏中的牛比 0PC 围栏中的牛采食时间更长（P<0.001），而 25PC 围栏中的牛比 0PC 围栏中的牛采食时间更短（P<0.001）。0PC 围栏中的牛非活动时间最长（P<0.01）。总之，无论混合与否，预处理牛在饲养场的前 3 周内花费更多时间采食、反刍和活动，而花费更少时间不活动。HC 浓度并不能确定与牧场转移相关的潜在较低压力，也与 BRD 相关发病率或 ADG 无关。
