Benefits of lung scanning for respiratory disease in calves
© Adobe Stock A study involving eight commercial dairy farms has flagged up the value of scanning calf lungs for respiratory disease damage.
Some two-thirds of the animals found with lesions had never had any clinical symptoms.
Bovine respiratory disease (BRD) is a major cause of mortality and morbidity in dairy calves, and has a severe impact on their welfare and growth rates, as well as their future performance as lactating cows.
See also: How scanning can detect early pneumonia in calves
As part of a Farming Connect-funded project in Wales, 256 calves were scanned using thoracic ultrasound (TUS) at between six and 10 weeks old.
Farming Connect lung scanning study
- Timeline of scanning from February to September 2024
- Herd sizes of 80-650 cows
- Block calving on three farms
- All-year-round calving on five farms
- All farm staff involved in calf rearing given training on detecting clinical signs of bovine respiratory disease
The scanning, which uses high-frequency sound waves to capture live images of internal body organs, revealed abnormal lung lesion scores in 54 calves and these animals were scanned again four weeks later.
Farm records showed, however, that only 33.3% of those 54 calves had previously shown signs of respiratory disease such as a cough, nasal discharge, drooping ears, and depression, and then been treated with an antimicrobial and an anti-inflammatory.
The others had not been treated, which suggests their symptoms were subclinical, says one of the vets involved in the study, Bedwyr Roberts of Daleside Veterinary Group, north Wales branch (see tables).
Growth rates hit
But what was evident was how that damage had impacted on growth rates.
Data analysis revealed average daily liveweight gain (DLWG) in the calves with abnormal scores was 0.17kg/day less than those without lesions.
Bedwyr says there were not enough calves with abnormal scores that had also been treated, to enable any difference in growth rates to be compared with the calves without lesions.
Records showed that on four of the farms, BRD had gone undetected and, therefore, untreated.
Scanning, however, flagged up that there had been an issue, emphasising how this procedure can find historic cases of BRD when symptoms have otherwise been missed, and so there is no record of treatment, he adds.
“This suggests clinical cases of BRD are just the tip of the iceberg, and its impact on calf growth and performance may affect many more calves than those showing clinical signs,’’ he says.
“This emphasises – and raises awareness of – the importance of monitoring calf health and performance, along with good calf management to minimise BRD.’’
What the study also revealed was that half of the calves with abnormal lung scores at the first scanning had normal scores at the second.
If there are surplus heifers on a farm, Bedwyr says TUS could form part of the decision tree on which to retain as replacements, to ensure that only the most productive animals form the future herd.
More calves scanned
Farming Connect specialist manager Menna Williams oversaw the project.
She says by assessing the level of lung consolidation, awareness had been raised on the study farms about the level of subclinical respiratory disease in dairy calves, and its potential impact on herd efficiency and profitability.
There are benefits to the dairy industry in general, and another 100 calves across the study farms will be scanned in 2025, she adds.
“This information will help motivate improvements in calf management on dairy farms, with the aim of reducing respiratory disease and reducing the need for antimicrobial use in calves.’’
Lesion results from ultrasound |
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| Farm |
Number of calves examined |
Calves with normal lung lesion score (%) |
Calves with abnormal lung lesion score (%) |
| 1 | 19 | 94.7 | 5.3 |
| 2 | 21 | 90.5 | 9.5 |
| 3 | 38 | 57.9 | 42.1 |
| 4 | 12 | 66.7 | 33.3 |
| 5 | 33 | 97 | 3 |
| 6 | 38 | 71.1 | 28.9 |
| 7 | 12 | 33.3 | 66.7 |
| 8 | 83 | 86.7 | 13.3 |
|
Source: Farming Connect |
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Calves treated and untreated |
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| Farm |
Calves with abnormal lesions untreated (%) |
Calves with abnormal lesions treated (%) |
Calves with normal lesion scores treated (%) |
| 1 | 0 | 100 | 5.3 |
| 2 | 100 | 0 | 9.5 |
| 3 | 100 | 0 | 42.1 |
| 4 | 25 | 75 | 33.3 |
| 5 | 100 | 0 | 3 |
| 6 | 27.3 | 72.3 | 28.9 |
| 7 | 25 | 75 | 66.7 |
| 8 | 100 | 0 | 13.3 |
|
Source: Farming Connect |
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Managing calves to prevent respiratory disease
Cases of respiratory disease can be prevented with good calf management protocols.
Vet Bedwyr Roberts of Daleside Veterinary Group says everything from housing and bedding to colostrum intakes and stocking density must be considered.
He recommends housing calves in purpose-built facilities and getting the right balance between fresh air coming into the building, but with no draughts at calf height.
He advises following Red Tractor guidelines on stocking density to avoid overcrowding.
Colostrum quality and intake quantities play a vital role in providing calves with the antibodies they need for disease prevention.
Farmers can use a refractometer to assess quality; then, to establish if passive transfer of immunity has been achieved, ask their vet to blood test a representative number of calves.
Bedding should be clean and dry “to not squelch underfoot when it is walked on’’, says Bedwyr.
While not every farm will have the facilities to isolate calves displaying clinical signs, he highly recommends that, where possible, they are.
Case Study: Rhys Davies, Moor Farm, Holywell, Flintshire
Rhys Davies © Farming Connect
Farm Facts
- Ffrwd pedigree herd
- 113 Holstein Friesians plus followers
- Milk yield average of 7,500 litres at 4.59% fat and 3.65% protein
- 618kg milk solids a cow
Cases of pneumonia
The combination of spring calving and a well-ventilated rearing shed means cases of pneumonia in calves are very rare at Moor Farm, near Holywell, Flintshire.
But with a high replacement rate, the Davies family need to be confident that every heifer entering their herd is capable of delivering her milk yield potential.
Lung scanning revealed just one calf with an abnormal score in the 2024-born heifers from the Holstein Friesian pedigree herd.
The score was not high and the calf had not displayed any clinical symptoms of respiratory infection.
Calf rearing
Maintaining a tight calving block of eight weeks puts the herd replacement rate at 33%, so attention to detail is a priority during calf rearing.
Newborn calves spend their first couple of days in pairs in small, straw-bedded pens before moving into a group of 10, reared on whole milk until weaning at eight weeks.
The rearing shed is airy with an open ridge, very different from the traditional barns where calves had previously been housed, says Rhys Davies, who farms with his parents Dei and Heulwen.
“We had more cases of pneumonia when we were rearing in those barns,’’ he recalls.
Heifers are weighed regularly to keep them on target for mating at 15 months at between 350-380kg, depending on genetics.
Calving previously got under way in mid-February but that has now shifted to 20 March.
The land at Moor Farm is quite heavy and a succession of wet Februarys was one of the reasons the Davies’ pushed calving back, as well as their milk buyer’s seasonality price penalties.
Routine scanning
Because the farm has a good track record of calves not contracting respiratory infections, Rhys says he would not routinely use lung scanning.
He does, however, see a good case for it in other systems where there is more pressure on calves at times of the year when the weather conditions are conducive to pneumonia.
“If I were autumn calving and the housing wasn’t great, I think it would be well worth that investment to check the extent of any lung damage before heifers joined the herd,’’ he says.
Rhys also wonders if there might be potential to use it to work out if there is a correlation between the genetic link to calf survivability and an abnormal lung score.
“It might help us to more accurately pinpoint the heifers to breed from,’’ he suggests.