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BOVINE RESPIRATORY DISEASE (BRD)
The cattle respiratory tract hosts a complex community of viral and bacterial microorganisms which normally exist without causing disease. However, given the appropriate combination of low calf immunity, stress, inadequate nutrition and environmental factors, many of these microorganisms have the potential to cause lung damage (either alone or in combination) associated with BRD.1
Due to this, the risk of BRD is always present and incidence on-farm may be higher than previously thought due to the presence of clinical and subclinical BRD.
In a recent farmer survey, 68% of farmers indicated they had calves which suffered from BRD on their farms and 48% of farms had calf mortality due to BRD.2
PREVENTING BRD
Improving an individual animal’s disease resistance through immunity-led prevention should be your farmers primary focus to build a healthy herd on strong foundations.
The development of immunity-led prevention starts with excellent colostrum management and continues with utilising a robust vaccination programme. This is then supported by ensuring the animal’s nutrition, environment and management interactions (transport, weaning etc.) are all as good a standard as possible to minimise animal stress which can impact the immune system.
WHAT YOU CAN'T SEE – CLINICAL AND SUBCLINICAL BRD
The BRD you see on your clients farm’s could be just the tip of the iceberg as clinical BRD is estimated at 11-16% but subclinical disease much higher at 23-67%.7
This disease prevalence is shown in the infographic below which highlights the potential issue which is currently not seen on-farm
As subclinical BRD has the potential to be reducing productivity and profitability this could have a big impact.
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CLINICAL BRD
Clinical signs of BRD usually develop 5 to 14 days following stressful processes which put a strain on a calf’s immunity, such as rehousing, weaning or handling.3
Even once these clinical signs develop, it can be tricky to catch and treat BRD before lung damage occurs. On average, farmers detected BRD clinical signs 47 hours after the onset of fever.4 By this point, significantly, potentially permanent lung damage will have occurred.
As spotting BRD signs in calves can be so difficult, prevention will always be more efficient than cure.
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SUBCLINICAL BRD
Subclinical BRD is the existence of lung damage from BRD but without the overt clinical signs of disease. Due to this it is harder to quantify than clinical BRD because it relies on being able to visualise lung damage (through tools such as Thoracic Ultrasound (TUS)).
As subclinically infected animals still have lung damage, they will have a longer age to first calving, produce less milk or take longer to finish.5,6 As these animals may not have been highlighted as suffering from BRD as youngstock they can pose a hidden risk of the future production efficacy and profitability for your farmers.
Lung lesion as detected by ultrasound
WHAT YOU CAN SEE – THORACIC ULTRASOUND (TUS)
TUS can help the vet and farmer detect, visualise and score BRD cases which can:
- Validate the total prevalence and severity of BRD to help segment heifers to rear for replacement or those to sell
- Help to demonstrate the value of vet-farmer engagement in changing the conversation on-farm to focus on early-life prevention strategies and maximising life-time productivity
- Can be used to map high risk periods and produce farm specific prevention plans to reduce disease rates and antibiotic use
Given appropriate training and practice vets can utilise TUS to scan calf lungs, please speak to your MSD Animal Health Account Manager for further information
TUS EXAMPLES
The below images show the difference between healthy lung and a lung that has been damaged by BRD. As calves have a smaller lung capacity compared to other animals, further decreased lung capacity has a significant lifetime impact.8
A: Healthy lung B: Severe and extensive lesion preventing air flow through the entire lung lobe
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1. PLEURAL IRREGULARITY OR THICKENING
The early lung anomalies associated with pneumonia and that can be observed with TUS consist in the observation of several B lines which are numerous hyperechoic parallel lines due to reverberation artefacts associated with small reflective surfaces within the plural space. These lesions can also be observed in case of lung oedema and in diffuse parenchymatous disease.
A: Thickening of the pleura (lung lining) leads to B lines seen on TUS and oedema (fluid accumulation) seen on this post mortem -
2. PLEURAL CONDITIONS
Pleuritis and bronchopneumonia are characterised by ventral accumulation of fluid with variable quantity of echoic fibrin strands which may be accompanied by consolidation of the underlying lung lobes.
A: Thickening of the pleura (lung lining) leads to B lines seen on TUS and oedema (fluid accumulation) seen on this post mortem -
3. LOBULAR LESIONS
In the visual below, p a lesion due to inflammation can be seen. A typical single lobular lesion is a small area of consolidation within an otherwise aerated lung lobe. A consolidated lung has a hyperechoic appearance close to the liver echotexture.
A: Consolidation -
4. ABSCESSES
The images below feature abscesses. These can also be observed with a thick capsule and heterogenic content.
AGE & IMPACT OF BRD
When assessing the age at which calves being to suffer from lung consolidation, a study of 39 herds where 6-12 calves were scanned showed consolidation starting from as young as 2 weeks of age. This clearly demonstrates the need to protect against disease as early as possible.10
The above study defined positive lung consolidation as ≥ 3 cm, the below study of 1066 dairy calves aged 5-56 days shows the impact of having lesions of just 1-2 cm where calves grew respectively 96 g/d and 138 g/d less than calves without lesions.11
The same study tracked weights of the same calves over a longer period and showed a longer-term impact of lung lesions as identified by TUS.
BRD: LONG-TERM PRODUCTIVITY LOSSES
There are many production costs associated with BRD from decreased growth rates to increased age at first calving, carcass downgrading and the cost of mortality which should be considered. Here are some specific examples of the impact in dairy or beef systems to illustrate the high cost of BRD.
DAIRY PRODUCTIVITY LOSSES
The presence of BRD-related lesions in the first 8 weeks of life of a calf has been shown to give a 525kg (509 litre) decrease in milk production in the first lactation.5
BEEF PRODUCTIVITY LOSSES
Finished cattle with evidence of BRD at slaughter have been shown to have up to 202g reduction in weight gain per day from birth to slaughter.6
BRD: OUTBREAKS
BRD is a highly communicable disease and it should be contained from all angles. If it’s not properly protected against, it can lead to large economic losses which far outweigh the cost of prevention for the farmers.12
Often, the incubation period of BRD leads to the disease being passed from calf to calf before the farmer is even aware of the presence of BRD on the farm.9 The risks of an outbreak spreading through the whole group increases if animals in the group have low immune status, are kept in poor housing conditions with high stocking density and insufficient ventilation.
Developing excellent colostrum management practices and robust vaccination protocols which link with the animal journey on your farms is critical to protecting against outbreaks.
Contact your MSD Animal Health Account Manager to discuss how we can help you support your farmer’s disease prevention strategies.
References
- Lima et al. (2016) The upper respiratory tract microbiome and its potential role in bovine respiratory disease and otitis media. Scientific Reports 6: 29050
- National Youngstock Survey (2018) MSD Animal Health
- Makoschey (2008) Prevention of respiratory disease in cattle. International Dairy Topics. Vol 7:5
- Timsit et al. (2009) Rational treatment of respiratory disorders in young bulls, at fattening units in France. Proceedings EBF, Marseilles
- Dunn et al. (2018) The effect of lung consolidation, as determined by ultrasonography on first-lactation milk production in Holstein dairy calves, J. Dairy Sci., 101:1-7
- Williams & Green (2007) Associations between lung lesions and grade and estimated daily live weight gain in bull beef at slaughter. Cattle Practice, Vol.15 (No.3). pp. 244-249
- Ollivett & Buczinski (2016) On-Farm Use of Ultrasonography for Bovine Respiratory Disease. Veterinary Clinics of North America Food Animal Practice 32(1):19-35
- Ollivett et al. (2015) Thoracic Ultrasonography and Bronchoalveolar Lavage Fluid Analysis in Holstein Calves with Subclinical Lung Lesions. J Vet Intern Med. 29(6):1728-34
- Griffin (2014) The monster we don’t see: Subclinical BRD in beef cattle. Animal Health Research Reviews, 15(2), 138-141.
- Buczinski et al. (2018) Herd-level prevalence of the ultrasonographic lung lesions associated with bovine respiratory disease and related environmental risk factors. J. Dairy Sci. 101:2423-2432
- Tejero & Bach (2016) The hidden cost of a hidden disease: growth performance of calves as affected by bovine respiratory disease diagnosed using ultrasonography, Journal of Animal Science, Volume 94, Issue 5, 48
- Penny (2015). The control of bovine respiratory disease (BRD) are we making progress? Cattle Practice 23: 314-319
