The recent Cattle and Sheep Health and Welfare Survey by Ruminant Health and Welfare (2021) listed bovine respiratory disease (BRD) in the top five syndromes affecting cattle production and welfare in the UK. This will come as no surprise as it remains an important health and welfare issue affecting the UK cattle industry.
The impact BRD can have on productivity is often significant; it is more evident in the short term, but the longer-term impacts are no less important and may actually be less well recognised or accepted.
Prevention is key
Colostrum is, of course, key to calf health. Calves with failed transfer of passive immunity (FTPI), classified as serum total protein (STP) less than 5.7g/l, had 1.6 times greater odds of being treated for BRD than other calves (Windeyer et al., 2014).
There are numerous BRD vaccines available on the UK market, but with uptake consistently under 40 percent between 2013 and 2019 (CHAWG, 2020) there is certainly room for the use of vaccination to increase.
Recent internal research by Ceva Animal Health revealed that farmers, while correctly identifying external factors, were often uncertain about the pathogens responsible for disease on their farm
Recent internal research by Ceva Animal Health revealed that farmers, while correctly identifying external factors, were often uncertain about the pathogens responsible for disease on their farm (Ceva, 2021).
Considering the multicausal nature of BRD (environment, host immunity and management), it is no surprise that the disease is still frequently diagnosed, resulting in animals requiring treatment every year.
Impact of BRD
Farmers who were questioned about the impact of BRD on their animals recognised the short-term implications clearly, as well as the longer-term impact of severe disease (Ceva, 2021). However, they were possibly less aware of the impact which mild to moderate disease, and associated lung lesions, could have on lifetime performance.
In dairy heifer calves the impact of calfhood BRD features in many scientific publications. Some recent findings include:
- A 4.7 times greater risk of being culled if lung consolidation was diagnosed at weaning compared to no lung consolidation (Teixeira et al., 2017)
- Calves treated for BRD in the 60 days post movement to group housing were almost half as likely to calve down before 25 months (Stanton et al., 2012)
- A reduction in conception rate to first AI in maiden heifers from 62 percent to 52.5 percent (Teixeira et al., 2017)
- A reduction in the first lactation 305-day milk yield of 525kg (Dunn et al., 2018)
There are less published data in both dairy-bred and suckled beef calves; the main impact reported is an estimated reduction in daily live weight gain of up to 0.2kg (Bartram et al., 2017).
Early detection
To reduce both these short- and long-term impacts it is essential that BRD is detected and then treated early. There are many publications that suggest that early detection is not easily achieved. When post-mortem lung lesions are correlated to ante-mortem diagnoses and/or treatments, there is a significant discord. In one study only 61.8 percent of animals with pulmonary lesions were visually detected and treated ante-mortem (White and Retner, 2009), and in a more recent study only 47 percent of animals with severe lung lesions and 31 percent of animals with moderate lung lesions had been treated (Williams et al., 2016).
The variability in how animals respond to the disease, along with cattle’s tendency to mask signs of sickness, presents a diagnostic challenge for farmers (Weary et al., 2009). This often results in delays in identifying which animals require treatment
The challenge is being able to detect BRD visually. The sensitivity of visual identification is reported as between 60 and 70 percent (White and Retner, 2009) but with better specificity. The variability in how animals respond to the disease, along with cattle’s tendency to mask signs of sickness, presents a diagnostic challenge for farmers (Weary et al., 2009). This often results in delays in identifying which animals require treatment. A further diagnostic complication is that cattle can appear clinically healthy even when over 30 percent of the lung is rendered non-functional by pneumonia (Bassel et al.,2020).
While the farmers questioned in Ceva’s research believed that they were quick to identify, diagnose and treat an animal with BRD, which is key to minimising the impact, the disease can be difficult to detect using only visual clinical signs without handling (Ceva, 2021).
Clinical signs
Feed intake
Many of the farmers questioned mentioned using feed intake and change in demeanour as initial signs of disease in calves (Ceva, 2021).
A reduction in voluntary feed intake (VFI) can certainly be an indicator of ill health for a variety of reasons. In feedlots, studies have recorded cattle visits to the feed bunker, and it has been shown that BRD-affected animals have less frequent visits to the feed, and for less time (Sowell et al., 1999). The use of cumulative sum charts for feeding times predicted the majority of cattle with BRD 4.5 days before the observation of visual signs (Quimby et al., 2001). Another study using a predictive algorithm of feeding data identified BRD-affected cattle seven days before visual identification, with 60 to 81 percent of BRD cases classified as sick (Wolfger et al., 2015).
In feedlot cattle, feeding behaviour can help identify BRD-affected cattle earlier than visual detection (Wolfger et al., 2011)
Therefore, in feedlot cattle, feeding behaviour can help identify BRD-affected cattle earlier than visual detection (Wolfger et al., 2011). Further studies may evaluate technology for use in younger calves.
Pyrexia
Although non-specific, one of the first clinical signs is pyrexia. However, two-thirds of the farmers questioned did not routinely take the temperature of calves, possibly because it involves extra handling or there is no thermometer readily available.
Pyrexia is seen about two days (50 hours) before other clinical signs may be apparent (Timsit et al., 2011a). In another trial, 73 percent of steers with pyrexia (measured by reticulo-ruminal boluses) lasting longer than six hours and not visually detected were subsequently confirmed as BRD cases based on a rectal temperature greater than 39.7°C and abnormal pulmonary sounds (Timsit et al., 2011b).
A rise in body temperature may provide first evidence of BRD, but further clinical evaluation of suspect animals is necessary to reach a confirmed diagnosis as pyrexia is not specific to BRD (Timsit et al., 2011b)
The study additionally provided evidence that the first clinical signs detectable by visual appraisal appear between 12 and 136 hours after hyperthermia. Therefore, a rise in body temperature may provide first evidence of BRD, but further clinical evaluation of suspect animals is necessary to reach a confirmed diagnosis as pyrexia is not specific to BRD (Timsit et al., 2011b).
Further clinical signs
The first clinical sign indicative of BRD observed after the onset of pyrexia is nasal discharge (Timsit et al., 2011b). In this study, this was observed, on average, 24 hours after the beginning of pyrexic episodes, with a median of 19 hours and a range of 12 to 77 hours (Timsit et al., 2011b).
Other BRD clinical signs were abnormal pulmonary sounds (median: 39 hours, range: 12 to 77 hours), depression (median: 51 hours, range: 12 to 123 hours), cough (median: 65 hours, range: 27 to 136 hours) and eventually ocular discharge (median: 80 hours, range: 66 to 89 hours).
Farm management and protocols
A structured programme for monitoring animals could help in earlier diagnosis and treatment. It is essential that this programme starts early as BRD can be seen in very young calves: across 11 UK herds, BRD was diagnosed in 45.9 percent of calves before nine weeks of age, with 5 percent of calves having a diagnosis of BRD in their first week of life (Johnson et al., 2017).
A structured programme for monitoring animals could help in earlier diagnosis and treatment. It is essential that this programme starts early as BRD can be seen in very young calves
Having protocols in place to plan, prevent and protect against BRD is essential to mitigate the risk posed by BRD.
Plan
| Age of calf in days | Lower critical temperature (°C) |
|---|---|
| 1 | 13.4 |
| 5 | 12.2 |
| 10 | 10.8 |
| 15 | 9.5 |
| 20 | 8.4 |
| 25 | 7.3 |
| 30 | 6.4 |
- Ensure housing has good ventilation but no draughts
- If buying in cattle, do not mix with others immediately. If possible, house in a separate air space and implement the farm vaccination protocol, or buy from farms with known vaccine programmes
- Plan for what to do in severe weather conditions; for example, if it is very cold and below the lower critical temperature (LCT) (Table 1), assess how much milk calves require to meet maintenance and growth requirements, and consider providing coats
- Use herd health planning (HHP) to have protocols in place for monitoring and recording, as well as setting intervention levels for further or repeat diagnostics
Prevent
- Ensure that all calves get sufficient high-quality colostrum within six hours of birth
- Be in compliance with vaccine protocols
- Minimise stress when handling
- Ensure that disbudding is done at an appropriate age using a minimally invasive technique with local anaesthetic and NSAIDs
Protect
- Have a robust protocol for checking and assessing animals to improve early detection and treatment of those affected by BRD
- Monitor their feed intake and if in doubt check for pyrexia as early signs of disease incursion
- Remove affected animals from group pens to allow closer monitoring, ideally in a separate air space although this is often impractical or too late
Put a clear treatment protocol in place that everyone who works with the youngstock is aware of. The use of NSAIDs for every case on an analgesic (welfare) basis is easy to justify and also provides antipyretic action to help with VFI as well as anti-inflammatory action.
