Nearly a third of calves in the UK experience bovine respiratory disease and subclinical pneumonia, according to new Royal Veterinary College research.
It is hoped the findings will support vets in identifying the optimal techniques to use to precisely diagnose the condition, supporting bovine welfare.
Around 1.4m dairy calves are born in the UK each year, yet bovine respiratory disease is one of the leading causes of disease in pre-weaned calves and is the main reason for antibiotic use in this population.
However, diagnosis of the condition is challenging and has traditionally involved the assessment of clinical signs using scoring methods such as the Wisconsin Respiratory Score.
This method identifies disease based on visible signs including cough, nasal or ocular discharge, ear position and temperature.
However, more precise techniques for the diagnosis of disease are available, such as thoracic ultrasound, which can help to diagnose the condition with greater precision.
As part of the new study, the research team at the Royal Veterinary College (RVC) sought to combine both techniques to measure disease levels in UK dairy herds.
This is the first study of its kind to explore the frequency of bovine respiratory disease using thoracic ultrasound in a large subset of English dairy herds.
Researchers measured the occurrence of bovine respiratory disease in 476 calves born on 16 dairy farms located in south-west England.
They performed a total of 3,344 weekly exams from birth until weaning, measuring the respiratory health of calves using both ultrasound and scoring techniques.
The research revealed that the peak prevalence of lung consolidation, where air in the lungs is replaced by a solid, fluid or other material, occurred at 8 weeks of age, reaching 29%.
It also found that subclinical pneumonia, the presence of lung consolidation without outward clinical signs, was common.
At any week of age, up to 28.7% of calves were diagnosed with subclinical pneumonia, the RVC's research showed.
These findings demonstrate that subclinical pneumonia was common in the UK population of dairy-born calves, but diagnosis could easily be missed if stakeholders only observed clinical signs.
Clinical respiratory scoring will not identify all cases of bovine respiratory disease and thoracic ultrasound is an essential diagnostic technique which should be implemented by vets in clinical practice to support cattle welfare, it concluded.
George Lindley, lead author said: “The results of this study demonstrate that bovine respiratory disease, including lung consolidation identified via thoracic ultrasound, is common in pre-weaned calves born on UK dairy farms.
"Whilst the disease has negative welfare consequences, affecting growth, survivability and future productivity, our research suggests that a significant proportion of calves may remain undiagnosed when assessed by clinical signs only.
"Thoracic ultrasound is fast and relatively easy to perform and we hope that more widespread engagement will help to improve youngstock health and performance.”
