Bovine respiratory disease complex (BRD) is a major calf disease during the preweaning period. Thoracic ultrasound (TUS) has been recently described as a reliable tool for assessing BRD-associated lung lesions. The objectives of this study were to define the herd-level prevalence of lung consolidation assessed by TUS (CONSTUS). A total of 39 Québec dairy herds were randomly chosen to participate in this cross-sectional study. Between 6 and 12 preweaned calves were examined for signs of CONSTUS defined by any site with ≥3 cm consolidated lung tissue during 1 visit in summer and 1 visit in winter. Herd questionnaire focused on calf health and housing data [airborne bacteria (aerobic, coliform, yeasts and mold counts), air drafts, temperature, hygrometry, and ammonia levels] were also collected during these visits looking for potential association with CONSTUS prevalence. The median herd-level of CONSTUS prevalence (interquartile range) were 8% (0–22%) in summer and 15% (0–35%) in winter. Multivariable analyses showed that season was associated with an increased CONSTUS prevalence [10.0 vs. 19.3%; odds ratio (OR) = 2.16], as well as group housing during preweaned period (9.6 vs. 20.0%; OR = 2.37) and perceived BRD problem by the farmer (10.6 vs. 18.3%; OR = 1.89). Despite tremendous changes in calves' environment between winter and summer, none of the housing variables were associated with the CONSTUS prevalence in this study. Based on the observed CONSTUS prevalence ranges in the present study (herds in the lower prevalence quartile), an achievable goal of none of 12 calves with consolidation ≥3 cm can potentially be used to define a low-BRD risk herd.

牛呼吸系统疾病综合症（BRD）是断奶前的主要小腿疾病。胸腔超声（TUS）最近已被描述为评估与BRD相关的肺部病变的可靠工具。这项研究的目的是确定通过TUS（CONSTUS）评估的肺巩固的畜群水平患病率。总共随机选择了39个魁北克奶牛场参加这项横断面研究。在夏季的1次访问和冬季的1次访问中，检查了6至12只断奶前的犊牛的CONSTUS征象，该征象由肺组织≥3 cm固结的任何部位确定。牛群调查问卷着重于小牛的健康状况和住房数据[空气传播的细菌（需氧，大肠菌，酵母和霉菌数量），空气流通，温度，湿度，在这些访问中还收集了氨和[氨]水平，以寻找可能与CONSTUS患病率相关的信息。夏季，CONSTUS患病率的中位牧群水平（四分位间距）为8％（0–22％），冬季为15％（0–35％）。多变量分析显示，季节与CONSTUS患病率升高相关[10.0 vs. 19.3％; 比值比（OR）= 2.16]，以及断奶前的集体住房（9.6 vs. 20.0％； OR = 2.37）和农民认为的BRD问题（10.6 vs. 18.3％； OR = 1.89）。尽管冬季和夏季之间犊牛的环境发生了巨大变化，但在本研究中，没有任何住房变量与CONSTUS患病率相关。根据本研究中观察到的CONSTUS患病率范围（牧群处于较低患病率四分位数），