Hidden colostrum failures leave calves exposed despite 'high-quality' milk

More than three-quarters of calves on one dairy farm failed to absorb enough immunity from colostrum — despite it testing as “high quality” — according to a newly published case report.

The findings highlight a hidden but costly issue behind calf scours, with researchers warning that relying on colostrum quality alone can leave calves dangerously exposed to disease.

The report, published in Vet Record, examined a seasonal-calving dairy herd in Northern Ireland where over 75% of calves tested showed inadequate passive transfer, meaning they did not absorb enough protective antibodies after birth.

This was despite colostrum consistently meeting the recommended minimum of 22% Brix. All calves on the unit later developed scours.

Authored by Dr Ryan Davies of Veterinary Technical Consulting Ltd and Dr Katie Denholm of the University of Glasgow, the case study stresses the importance of testing calves directly using blood samples taken between 24 hours and seven days of age.

The authors say this approach provides a far clearer picture of immunity than colostrum testing alone.

The findings are particularly relevant for farms investing in dry cow vaccination programmes, as calves will not benefit from vaccine-derived antibodies if absorption fails.

Dr Davies said misconceptions around vaccination and colostrum management are common.

“It can often be a case of farmers jabbing the dry cows and thinking the job is done,” he said.

“When they then see diarrhoea in calves, they assume the vaccine isn’t working.”

However, he said testing on the case study farm showed the opposite.

“As the case study in our paper has shown, that wasn’t the case at all,” he said.

“Calves were still getting scours caused by Bovine rotavirus A (BRV-A) genotype G6P11, despite being vaccinated, as a result of inadequate colostrum management protocols.”

Analysis confirmed that colostrum contained sufficient protective antibodies, demonstrating successful vaccine efficacy.

“We know this because when the colostrum was tested it had sufficient protective antibodies to BRV-A,” Dr Davies said.

However, on-farm practices were not enabling optimal transfer of immunity in many calves.

On the unit studied, 81% of calves had serum total protein levels below 5.2 g/dL, indicating poor or only fair passive transfer.

Delayed feeding — linked to limited colostrum pasteuriser capacity — and wide variation in colostrum quality between cows were identified as major contributing factors.

Colostrum Brix readings ranged from 20% to 30%, increasing inconsistency in antibody delivery.

The findings suggest the issue may be far more widespread, supporting earlier research from the Royal Veterinary College which found failure of passive transfer in more than a quarter of calves across 91 UK herds.

In response, the Northern Irish farm made several changes, including feeding all calves within 30 minutes of birth.

Colostrum was enriched using whole bovine colostrum powder to standardise quality at 30% Brix.

Extended colostrum feeding was also introduced for the first 10 days of life.

Dr Denholm said meeting minimum thresholds alone may not be sufficient.

“While 22% Brix is the minimum requirement, calves benefit from 300 g of IgG – and more where multiple feeds are given – to meet passive immunity targets,” she said.

She added that extended colostrum or transition milk feeding can support gut health even after antibody absorption declines.

Both vets warned that hygiene is critical when collecting, storing and feeding colostrum.

“Bacteria interferes with IgG absorption, so if your hygiene is poor, you won’t see the benefits of colostrum or extended feeding,” Dr Davies said.

“It’s essential to scrub and clean all equipment with hot water, brushes and detergents.”

Dr Denholm said there is no single solution that suits every farm.

“It’s not just about quality — timing, volume, cleanliness, cow health, speed of collection and storage conditions all play a role,” she said.

“A weakness in any part of the chain can undermine the whole system.”

She said relatively simple changes could prevent significant losses.

“Simple adjustments such as reviewing collection practices, checking feeding speed and volumes, logging timings, or re-evaluating storage methods — could make the difference between successful passive transfer and costly disease outbreaks,” she said.

The authors said early testing and tailored protocols could help farms prevent scours, protect calf health and avoid the significant financial and welfare costs associated with disease outbreaks.