More than three-quarters of calves on a dairy farm did not absorb enough immunity from their colostrum, even though it tested as “high quality”, according to a newly published case report.
The findings highlight a hidden but costly issue behind calf cleaning, with researchers warning that relying solely on colostrum quality can expose calves to dangerous diseases.
The report, published in Vet Record, investigated Northern Ireland’s seasonal dairy herd and found that more than 75% of calves tested showed inadequate passive transmission, meaning they did not absorb enough protective antibodies after birth.
This was despite colostrum consistently meeting the recommended minimum of 22% Brix. All calves in the unit subsequently developed scour.
This case study, written by Dr Ryan Davies from Veterinary Technical Consulting Ltd and Dr Katie Denholm from the University of Glasgow, highlights 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 much clearer picture of immunity than colostrum testing alone.
The findings are particularly important for farms investing in dry cow vaccination programs, as calves will not benefit if vaccine-derived antibodies are not absorbed.
Dr. Davis said misconceptions about vaccination and colostrum management are common.
“A lot of times, farmers hit a dry cow and think their job is done,” he says.
“Then if we see diarrhea in the calf, we think the vaccine is not working.”
However, he said tests at case study farms showed the opposite results.
“As the case study in our paper shows, that was simply not the case,” he says.
“Despite vaccination, the calf still suffered from versicolor caused by bovine rotavirus A (BRV-A) genotype G6P11 as a result of inadequate colostrum management protocols.”
Analysis confirmed that the colostrum contained sufficient protective antibodies, demonstrating the effectiveness of the vaccine.
“We know this because when we tested the colostrum, there were sufficient protective antibodies against BRV-A,” Dr. Davis said.
However, on-farm practices did not allow optimal transfer of immunity to many calves.
In the units studied, 81% of calves had serum total protein levels below 5.2 g/dL, indicating poor or negligible passive transfer.
Feeding delays related to limited pasteurization capacity of colostrum and large variations in colostrum quality between cows were identified as the main contributing factors.
Colostrum Brix measurements range from 20% to 30%, increasing discrepancies in antibody delivery.
The findings suggest the problem may be much more widespread and support earlier research from the Royal Veterinary College, which found that more than a quarter of calves in 91 herds in the UK were failing passive transfers.
In response, farms in Northern Ireland have made several changes, including feeding all calves within 30 minutes of birth.
Colostrum was fortified using whole bovine colostrum powder and quality was standardized at 30% Brix.
Long-term colostrum feeding was also introduced during the first 10 days of life.
Dr Denholm said meeting minimum standards may not be enough.
“While 22% Brix is the minimum requirement, calves benefit from receiving 300 g of IgG to achieve passive immunization targets, and even more when fed multiple diets,” she said.
She added that long-term breastfeeding with colostrum or transitional milk can support gut health even after antibody absorption declines.
Both veterinarians cautioned that hygiene is important when collecting, storing and feeding colostrum.
“Bacteria interfere with the absorption of IgG, so poor hygiene makes colostrum and prolonged breastfeeding ineffective,” says Dr. Davis.
“It’s important to scrub all equipment using hot water, a brush, and detergent.”
Dr Denholm said there was no single solution that would suit all farms.
“Quality is not the only thing that matters – timing, quantity, cleanliness, cow health, speed of collection and storage conditions all come into play,” she said.
“A weakness in any part of the chain can compromise the entire system.”
He said relatively simple changes could prevent significant losses.
“Simple adjustments such as reviewing collection methods, checking feeding rates and amounts, recording timing, and reevaluating storage methods can make the difference between a successful passive transfer and a costly disease outbreak,” she said.
The authors said early testing and customized protocols could help farms prevent baptism, protect calf health and avoid significant financial and welfare costs associated with disease outbreaks.
