Bovine respiratory disease (BRD) is the main cause of mortality among 1-to-5 month old calves in Ireland, accounting for approximately one-third of deaths. Despite widespread use of clinical respiratory signs for diagnosing BRD, lung lesions are detected, using thoracic ultrasonography (TUS) or following post-mortem, in calves showing no clinical signs. This highlights the limitation of clinical respiratory signs as a method of detecting sub-clinical BRD. Using 53 purchased artificially-reared male dairy calves, the objectives of this study were to: (i) characterise the BRD incidence detected by clinical respiratory signs and/or TUS, (ii) investigate the association between clinical respiratory signs and lung lesions detected by TUS, and (iii) assess the effect of BRD on pre-weaning growth. Clinical BRD (based on Wisconsin clinical respiratory score and/or rectal temperature > 39.6 ºC) was detected in 43 % and sonographic changes (lung lesions) were detected in 64 % of calves from purchase (23 (SD; 6.2) days of age) until weaning, 53 days post-arrival. Calves with clinical BRD were treated. Sixty-one per cent calves affected with clinical BRD had lung lesions 10.5 days (median) before detection of clinical signs. Moderate correlations (rsp 0.70; P < 0.05) were found between cough and severe lung lesions on arrival day, and between rectal temperature > 39.6 ºC and lung lesions ≥ 2 cm2 on day 7 (rsp 0.40; P < 0.05) post-arrival. Mean average daily live weight gain (ADG) of calves from purchase to weaning was 0.75 (SD; 0.10) kg; calves with or without clinical BRD did not differ in ADG (P > 0.05), whereas ADG of those with severe lung lesions (lung lobe completely consolidated or pulmonary emphysema) was 0.12 kg/d less (P < 0.05) than calves without lung lesions. Thoracic ultrasonography detected lung consolidation in calves that did not show signs of respiratory disease. The presence of severe lung lesions was associated with reduced pre-weaning growth. These findings emphasise the importance of using TUS in addition to clinical respiratory scoring of calves for an early and accurate detection of clinical and sub-clinical BRD.

中文翻译：

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断奶前犊牛的临床呼吸道体征，胸部超声检查发现的肺部病变与生长性能之间的关联

牛呼吸道疾病（BRD）是爱尔兰1至5个月大的犊牛死亡的主要原因，约占死亡总数的三分之一。尽管广泛使用临床呼吸道征兆诊断BRD，但在没有临床征兆的小牛中，还是通过胸腔超声检查（TUS）或验尸后发现了肺部病变。这突显了临床呼吸道症状作为检测亚临床BRD的方法的局限性。本研究的目的是使用53种购买的人工饲养的雄性牛犊，来：（i）表征通过临床呼吸道症状和/或TUS检测到的BRD发生率，（ii）研究临床呼吸道症状与通过呼吸道疾病检测到的肺部病变之间的关联TUS和（iii）评估BRD对断奶前生长的影响。在购买的小牛中，有43％的人检测到了临床BRD（基于威斯康星州的临床呼吸评分和/或直肠温度> 39.6ºC），并且在64％的小牛中检测到了超声变化（肺部病变）（年龄为23（SD; 6.2）天）直到断奶，到达后53天。治疗患有临床BRD的小牛。受到临床BRD影响的61％犊牛在检测到临床体征前10.5天（中位）出现肺部病变。到达后第7天，咳嗽和严重肺部病变之间以及直肠温度> 39.6ºC和肺部病变≥2 cm2之间存在中等相关性（rsp 0.70; P <0.05）（rsp 0.40; P <0.05）。从购买到断奶的小牛平均日增重（ADG）为0.75（SD; 0.10）千克；有或没有临床BRD的小牛的ADG均无差异（P> 0.05），与没有肺部病变的小牛相比，具有严重肺部病变（肺叶完全合并或肺气肿）的ADG降低了0.12 kg / d（P <0.05）。胸腔超声检查未发现呼吸道疾病迹象的小牛的肺部巩固。严重肺部病变的存在与断奶前生长降低有关。这些发现强调了除了对小牛进行临床呼吸评分外，还应使用TUS进行早期和准确的临床和亚临床BRD检测。严重肺部病变的存在与断奶前生长降低有关。这些发现强调了除了对小牛进行临床呼吸评分外，还应使用TUS进行早期和准确的临床和亚临床BRD检测。严重肺部病变的存在与断奶前生长降低有关。这些发现强调了除了对小牛进行临床呼吸评分外，还应使用TUS进行早期和准确的临床和亚临床BRD检测。