Bovine respiratory disease (BRD) is the most important and costly health issue of the feedlot industry worldwide. Remote monitoring of reticulorumen temperature has been suggested as a potential tool to improve the diagnostic accuracy of BRD. The present study aimed to evaluate 1) the difference and degree of reticulorumen hyperthermia episodes between healthy and subclinical BRD feedlot steers, and 2) determine the correlation between reticulorumen hyperthermia and lung pathology, performance, and carcass traits. Mixed-breed feedlot steers (n = 148) with a mean arrival weight of 321 ± 3.34 kg were administered a reticulorumen bolus at feedlot entry and monitored for visual and audible signs of BRD until slaughter when lungs were examined and scored for lesions indicative of BRD. Post-slaughter animals with no record of BRD treatment were assigned to one of three case definitions. Healthy steers had no visual or audible signs of BRD (i.e., CIS=1), and total lung consolidation score < 5% or pleurisy score < 3 at slaughter. Subclinical BRD cases had a CIS of 1, and a lung consolidation score ≥ 5% or a pleurisy score of 3 at slaughter. Mild CIS cases had at least one CIS of 2, and a lung consolidation score < 5% and a pleurisy score < 3 at slaughter. Subclinical BRD and mild CIS cases had longer total duration of reticulorumen hyperthermia, more episodes and longer average episode duration above 40.0 °C compared to healthy steers (P < 0.05). A moderate positive correlation was found between lung consolidation and total duration (r = 0.27, P < 0.001), episode duration (r = 0.29, P < 0.001), and number of episodes (r = 0.20, P < 0.05). Pleurisy score was also found to be moderately and positively correlated with total duration (r = 0.23, P < 0.01), episode duration (r = 0.37, P < 0.001), and number of episodes (r = 0.26, P < 0.01). Moderate negative correlations were found between reticulorumen hyperthermia and carcass traits including hot standard carcass weight (HSCW) (−0.22 ≤ r ≤ −0.23, P < 0.05) and P8-fat depth (−0.18 ≤ r ≤ −0.32, P < 0.05). Subclinical BRD reduced carcass weight by 22 kg and average daily gain (ADG) by 0.44 kg/day compared to healthy steers (P < 0.05), but mild CIS cases had no effect on performance (P > 0.05). The reticulorumen bolus technology appears promising for detection of subclinical BRD cases in feedlot cattle as defined by lung pathology at slaughter.

中文翻译：

---

网状腔温度推注对饲养场牛呼吸道疾病亚临床病例诊断的评价

牛呼吸道疾病 (BRD) 是全球饲养场行业中最重要、成本最高的健康问题。网状腔温度的远程监测已被建议作为提高 BRD 诊断准确性的潜在工具。本研究旨在评估 1) 健康和亚临床 BRD 饲养场阉牛之间网状腔过热发作的差异和程度，以及 2) 确定网状腔过热与肺病理、性能和胴体性状之间的相关性。平均到达体重为 321 ± 3.34 kg 的混合品种饲养场阉牛 (n = 148) 在进入饲养场时被给予网状瘤推注，并监测 BRD 的视觉和听觉迹象，直到屠宰时检查肺部并对指示 BRD 的病变进行评分. 没有 BRD 治疗记录的屠宰后动物被分配到三个病例定义之一。健康的牛没有 BRD 的视觉或听觉迹象（即，CIS = 1），并且总肺实变评分 < 1。5% 或胸膜炎评分 <; 3 屠宰场。亚临床 BRD 病例的 CIS 为 1，肺实变评分 ≥ 5% 或屠宰时胸膜炎评分为 3。轻度 CIS 病例至少有一个 CIS 为 2，并且肺实变评分 < 1。5% 和胸膜炎评分 <; 3 屠宰场。与健康牛相比，亚临床 BRD 和轻度 CIS 病例的网状腔热疗总持续时间更长，发作次数更多，平均发作持续时间超过 40.0 °C (P < 0.05)。在肺实变和总持续时间 (r = 0.27, P < 0.001)、发作持续时间 (r = 0.29, P < 0.001）和发作次数（r = 0.20，P < 0.05）。还发现胸膜炎评分与总持续时间 (r = 0.23，P < 0.01)、发作持续时间 (r = 0.37，P < 0.001) 和发作次数 (r = 0.26，P < 0.001) 呈适度正相关。 0.01）。网状瘤胃热疗与胴体性状之间呈中度负相关，包括热标准胴体重量 (HSCW)（-0.22 ≤ r ≤ -0.23，P < 0.05）和 P8 脂肪深度（-0.18 ≤ r ≤ -0.32，P < 0.05）。与健康小牛相比，亚临床 BRD 使胴体重量减少 22 公斤，平均日增重 (ADG) 减少 0.44 公斤/天 (P < 0.05)，但轻度 CIS 病例对性能没有影响 (P > 0.05)。