Key results:
- 21.1% of the calves scanned in this study had abnormal lung lesion scores (scores >1).
- 33.3% of calves with abnormal lung lesion scores showed clinical symptoms of BRD and were treated with antimicrobials, whereas the remaining 66.7% did not receive any antimicrobial treatment suggesting subclinical disease.
- Across the study period, calves with abnormal lung lesion scores had lower growth rates on average by 0.17 kg/ day in comparison to calves with normal lung lesion scores.
Background:
Bovine respiratory disease (BRD) is a multifactorial disease that can be caused by a range of factors such as, pathogens (viruses and bacteria), host-related factors, environmental stressors and management practices. This disease can negatively affect animal welfare and have negative effects on growth rates, fertility and milk production. Moreover, BRD is reported to be the main reason for antimicrobial use in calves and youngstock. As such, there is a need to reduce BRD on farm for the health and welfare of stock, economics and for reducing antimicrobial use.
Purpose of the work:
- Improve the health and welfare of dairy calves in Wales by raising awareness of the impact and importance of reducing bovine respiratory disease on farm.
- Investigate the use of thoracic ultrasound scanning as a diagnostic tool for the early detection of bovine respiratory disease in calves.
- Investigate the effects of bovine respiratory disease on calf growth rates.
What we did:
The project involved 8 dairy farms in Northeast Wales. Dairy heifers (n=256) aged 2-6 weeks were selected and weighed using a weigh tape. The same calves were re-weighed approximately 4 weeks later and a thoracic ultrasound (TUS) examination was performed by a veterinarian to assess the lungs for lesions. Scores of ≤1 were regarded as normal and scores of > 1 abnormal. Calves were revisited for a third time approximately 4 weeks after the TUS examination and re-weighed a final time. At the final weighing, TUS examinations were performed for a second time on calves that received abnormal scores to monitor disease progression. All farm staff were provided with training on the detection of the clinical signs of bovine respiratory disease based on an MSD Calf Health Score Card and each farm provided records of all clinical cases of BRD during the project.
Outcomes:
- In this project, approximately two thirds of the calves with abnormal lung lesions did not show any clinical signs of disease and therefore were not treated with antimicrobials. This suggests disease to be subclinical or to have gone undetected and that clinical signs of disease may be the “tip of the iceberg”.
- On average calves with abnormal lung lesion scores had lower growth rates in comparison to those with normal lung lesion scores, highlighting the negative effect of bovine respiratory disease on calf performance.
- Thoracic ultrasound scanning can act as a useful tool to;
- Assess bovine respiratory disease on farm (prevalence and severity)
- Detect disease and treat it before it manifests
- Identify calves with damaged lungs
- Act as a management tool for selecting replacement heifers
- Support decisions with antimicrobial use
How to apply on your farm:
1. Evaluate the health of calves on farm and consider cases of bovine respiratory disease.
2. Contact your farm vet about lung lesion scoring using thoracic ultrasound examinations. This could be done as part of your animal health and improvement cycle plan for the sustainable farming scheme.
3. Measure: Select a group of calves to undergo thoracic ultrasound examinations, ideally calves should be more than 3 months old and weigh more than 150 kg, it is also recommended to scan at stressful times when calves are most susceptible to disease e.g. weaning (AHDB, 2026).
4. Plan: Discuss results with your veterinarian, create a plan for any improvements needed and implement that plan on farm.
5. Review: Re-scan calves to measure the success of any changes made.