Lung scanning can detect respiratory disease in visibly healthy calves, new research from the Agri-Food and Biosciences Institute (AFBI) has shown.

A study by researchers at AFBI Hillsborough, funded by Feed For Growth (Volac Milk Replacers Ltd), used thoracic ultrasound scanning to investigate if bovine respiratory disease (BRD) can be present in calves which look healthy.

BRD, also known as pneumonia, is one of the leading causes of ill-health and mortality in calves.

The disease, which costs the UK cattle industry between £60 million and £80 million every year, is caused by bacteria or viruses and made worse by environmental factors including poor ventilation, low temperatures, and high humidity.

Calves are at a higher risk of contracting BRD if they do not receive enough good-quality colostrum at birth, which weakens their immunity.

Stressful events including disbudding, mixing with other animals, and weaning can also make the disease worse.

Diagnosing

Despite the impact of BRD, it remains difficult to diagnose because it can be present without visible clinical signs.

AFBI researchers investigated the presence of BRD during a wider study into calf nutrition.

As part of the study, 108 calves were offered different dietary treatments until they were 13 weeks-of-age.

Researchers recorded the calves’ feed intake every day and measured their live weight fortnightly.

Throughout the study, experts assessed calves for visual signs of respiratory disease three times a week.

Calves were also given lung scans when they were between five to six and 12 to 13 weeks-of-age, using the same portable scanning equipment that a vet would use for pregnancy scanning.

When calves were scanned at five to six weeks-of-age, most had healthy lungs.

Only 5.6% (six calves) showed moderate pneumonia, and none had severe lung damage.

Of those six calves, only two showed visual signs of respiratory disease.

When the calves were scanned again at 12–13 weeks-of-age, the number with moderate pneumonia had increased to 14.8% (16 calves).

However, none of these 16 calves showed obvious signs of respiratory disease.

Visibly healthy calves

The findings show that some calves can have BRD even though they do not appear to be ill.

AFBI researcher Dr. Gillian Scoley said: “The results of this study show that BRD can be present in visibly healthy calves, putting them at risk of reduced performance and efficiency throughout their lifetime.

“Using thoracic ultrasound scanning means that individual calves can be treated based on actual disease severity as opposed to relying on blanket treatments across groups of calves which also supports the responsible use of medicines."

Dr. Jessica Cooke from Feed For Growth said that nutrition can influence a calf's immune function and resilience to disease, so as part of the trial, the team wanted to see whether different nutritional planes affected lung health.

“Thoracic ultrasound scanning allowed us to look beyond visible clinical signs and objectively assess the lungs for both clinical and subclinical disease, giving us a clearer understanding of how nutrition may affect respiratory health during early life," she explained.

Iain Smith from Lisburn Veterinary Clinic, who carried out the scanning for the study, added that respiratory disease does not always show obvious signs.

He said: “Lung scanning allows us to detect hidden lung damage, evaluate how well vaccination programmes are protecting your calves, and make informed decisions about treatment and future prevention.

"Better information leads to healthier calves, improved welfare and increased productivity."

Signs of respiratory disease

AFBI said keeping a close eye on calves, particularly during periods of increased risk, can be helpful in identifying respiratory disease at an earlier stage.

Common clinical signs include:

Reduction in milk intake;
Flicking or drooping of the ears;
Discharge from the eye or nose;
Coughing;
High temperature (>39.5°);
Listless/dull;
Lifting/blowing.