Association between clinical respiratory signs, lung lesions detected by thoracic ultrasonography and growth performance in pre\u2010weaned dairy calves

Inmaculada Cuevas-Gómez,Nicky Byrne,José María Sánchez,Bernadette Earley,Tara Mcdaneld,Mark Mcgee,Edward O’Riordan

doi:10.1186/s13620-021-00187-1

Inmaculada Cuevas-Gómez, Nicky Byrne + Show 5 more

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https://doi.org/10.1186/s13620-021-00187-1

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Abstract

BackgroundBovine 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.ResultsClinical 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.ConclusionsThoracic 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.

Highlights

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
Of the 23 clinical BRD (cBRD) + calves, 14 had lung lesions present a median of 10.5 days before detection of clinical signs
AThoracic ultrasonography score (TUSS1; TUSS2 (Lung lesion < 2cm2; TUSS3 Lung lesions ≥ 2cm2; TUSS4 Consolidated lung lobe and or/emphysema) bClassification of calves considering the ultrasound evaluations performed from arrival to day 14 cClassification of calves considering the ultrasound evaluations performed from arrival to day 30 dcBRD- calves that had no BRD treatment from arrival until weaning ecBRD+ calves that had BRD treatment from arrival until weaning personnel other than a veterinarian [1, 8]

Summary

Introduction

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. The evaluation of clinical respiratory signs, whether through clinical respiratory score (CRS) charts, auscultation [8, 9] or subjective criteria (e.g. depressive attitude, appearance) [10], is the main approach used for diagnosing BRD and establishing criteria for treatment These methods are limited since they fail to detect calves with lung lesions but not showing clinical respiratory signs (sub-clinical BRD) [10, 11]. There are a limited number of studies evaluating the association between growth performance and TUS findings, in pre-weaned calves [11, 14]

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