Growth performance and hematological changes of weaned beef calves diagnosed with respiratory disease using respiratory scoring and thoracic ultrasonography

Authors: CUEVAS-GOMEZ, INMACULADA - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY); MCGEE, MARK - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY); MCCABE, MATTHEW - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY); CORMICAN, PAUL - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY); O'RIORDAN, EDWARD - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY); McDaneld, Tara; EARLEY, BERNADETTE - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY)

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2020
Publication Date: 10/23/2020
Citation: Cuevas-Gomez, I., McGee, M., McCabe, M., Cormican, P., O'Riordan, E., McDaneld, T.G., Earley, B. 2020. Growth performance and hematological changes of weaned beef calves diagnosed with respiratory disease using respiratory scoring and thoracic ultrasonography. Journal of Animal Science. 98(11):1-11. https://doi.org/10.1093/jas/skaa345.
DOI: https://doi.org/10.1093/jas/skaa345

Interpretive Summary: Bovine respiratory disease (BRD) is a complex disease, in which the interaction between infectious agents (bacterial, virus, fungi), external stressors and the animal’s immune system influence the development of the disease. This study investigated (i) the effect of clinical BRD and associated lung consolidations on growth performance and blood profiles of recently weaned beef calves and (ii) the relationship between clinical respiratory signs and lung consolidation detected by thoracic ultrasonography (TUS). One hundred and fifty-three weaned beef calves were purchased and transported from auction marts and accommodated indoors in slatted floor pens. Calves were periodically weighed until d 65 post-arrival. Assessment of BRD as well as TUS and collection of blood samples for blood profiles, were performed over the first 28 d. Assessment of BRD was performed through evaluation of five clinical respiratory signs, generating a sum for the clinical respiratory score (CRS). Using combined CRS+TUS scores, calves were classified as BRD (CRS+TUS =5, with or without lung consolidation), sub-clinical BRD (CRS+TUS <5 with lung consolidation) and healthy (CRS+TUS <5 without lung consolidation), respectively. Thoracic ultrasonography is a useful tool to detect lung lesions and its implementation in combination with CRS should provide a more accurate and early diagnosis of BRD, which is fundamental to successful treatment, animal welfare and performance.

Technical Abstract: This study investigated 1) the effect of clinical bovine respiratory disease (BRD) and associated lung consolidations on growth performance and hematological profiles of recently weaned beef calves and 2) the relationship between clinical respiratory signs and lung consolidation detected by thoracic ultrasonography (TUS). One hundred and fifty-three weaned beef calves (209 days old [SD: 35.8] and 306 kg [SD: 26.3], at arrival) purchased and transported from auction markets were accommodated indoors in concrete slatted floor pens. Calves were weighed weekly from arrival until day 28 and on day 65 post-arrival. Assessment of BRD and blood sample collection for hematological profiles were performed on scheduled days (at arrival, on days 7, 14, and 28) and on other days upon BRD diagnosis. Animals were assessed for BRD using a total clinical respiratory score (CRS) of five clinical signs (rectal temperature, ear position, cough, nasal secretion, and eye secretion with each ranging from normal [0] to abnormal [3]) and TUS scores (normal [0] to lung consolidation = 1 cm2 [2]). Based on CRS, 35% of calves were CRS+ (CRS = 5) and 65% were CRS- (CRS < 5). Although no lung consolidations (TUS-) were detected at arrival, 34% of calves developed lung consolidation (=1 cm2) (TUS+) during the first 28 d post-arrival. Only fever (>39.6 °C) and nasal discharge were weakly associated (r = 0.19, P <0.05) with lung consolidation. On the day of BRD detection, neutrophil number and neutrophil:lymphocyte ratio were 58% and 73% greater, respectively, in BRD calves with lung consolidation compared with healthy calves. From day 0 to 65, calf average daily gain (ADG) did not differ (P >0.05) between CRS+ and CRS- calves but was 0.09 kg/d lower (P < 0.05) for TUS+ compared with TUS- calves. Calves classified as BRD (CRS + TUS = 5) with lung consolidation had lower (P < 0.05) ADG from arrival until day 28 than healthy calves and BRD calves without lung consolidation (0.11 ± 0.10 vs. 0.53 ± 0.07 vs. 0.57 ± 0.10 kg/d, respectively); however, no differences in ADG were observed from day 0 to 65. Conventional methods to diagnose BRD failed to detect calves with lung lesions. TUS is a useful tool to detect lung lesions and its implementation in combination with CRS should provide a more accurate and early diagnosis of BRD, which is fundamental to successful treatment, animal welfare, and growth performance.