Smart Calf Rearing Conference – Beyond IgG: Colostrum’s critical role in shaping calf immunity

3 November 2025

8 minute read

By: Sarah Mikesell

Europe

North America

Editor's note: From September 25 to 27, the international Smart Calf Rearing Conference took place at the University of Madison in Madison, Wisconsin. Organized by Förster-Technik, Trouw Nutrition, the University of Guelph and the University of Wisconsin – Madison, the conference brought together 245 participants from around the globe to discuss the latest findings in calf physiology, health, housing and welfare, and 18 renowned speakers shared their expertise and research insights. Participants also had the opportunity to visit the university’s calf barn, where innovative solutions for calf rearing were showcased – including the CalfRail feeding system for individual housing, developed by Förster-Technik.

When a calf is born, its immune system faces a challenge unlike that of any other mammal. Calves enter the world essentially immunologically naïve, without the maternal antibodies that human infants receive in utero. In the first hours of life, colostrum becomes their lifeline – not just as a source of antibodies, but as a complex biological signal that shapes immunity, gut development and microbial colonization in the weeks that follow.

Dr. Lautaro Rostell Cangiano, assistant professor at the University of Wisconsin-Madison, shared new insights into colostrum’s multifaceted role during a recent presentation at the Smart Calf Rearing Conference held at the University of Wisconsin in Madison, Wisconsin, USA. His research indicates that colostrum is far more than a vehicle for passive transfer of IgG; it’s a biological programming tool that influences the calf’s immune trajectory long after the first feeding.

“Calves are born immunologically naïve. What does that mean? It means that the immune system has not been exposed yet to microbes in the environment. A lot of immune responses take time to mature, and the immune system has to recognize what's a commensal microbe from an actual pathogen and how to react to it. In the meantime, it's going to rely on and be protected by the passive immune transfer from colostrum provided by the dam,” said Dr. Cangiano.

The immunological starting line

Unlike humans, ruminant placentas do not allow for the transfer of maternal antibodies or immune cells before birth. This means calves rely entirely on colostrum for immunoglobulins (IgG), immune cells and bioactive factors. But as Dr. Cangiano explained, colostrum delivers much more than IgG. It contains growth factors such as insulin-like  growth factor (IGF-1), which drives intestinal development. It also contains nutrients, vitamins, cytokines and leukocytes, like T cells and B cells, that help regulate the cellular immune response during the critical window of early life.

He cited a 2020 study that redefined benchmarks for successful passive transfer and emphasized that even when antibody transfer is adequate, disease risk remains high, highlighting the need to understand colostrum’s broader functions.

He and his research team are exploring two questions: 

1. What is the role of colostrum programming and the development of immune system with animals beyond passive transfer?
2. What happens when you process colostrum in ways that might be removing the maternal cells or affecting some of the bioactive components?

“Colostrum is kind of like a driver of the development of the animal life,” he said.

Fresh vs. frozen study insights

To investigate colostrum’s impact, Dr. Cangiano’s team conducted a controlled experiment using three groups of calves: one deprived of colostrum, one fed fresh colostrum from their dam, and one fed frozen colostrum from their dam. All groups were raised in a high-biosecurity facility with filtered airflow to minimize environmental pathogen exposure. The design allowed researchers to isolate the effects of colostrum on immune development.

Calves received 10% of their body weight in colostrum at the first feeding and 6% at the second feeding. The team also vaccinated dams against specific pathogens during the dry period to track maternal antibody transfer and calf protection.

The results were clear: calves deprived of colostrum showed zero antibody transfer, confirming the well-known principles of passive transfer. Meanwhile, both fresh and frozen colostrum groups showed successful transfer, with no significant differences between them.

“This is well known in the industry, but there was no difference between fresh and frozen colostrum fed to calves,” he explained. “I think the main message is if you have a prevalence of a specific disease on your farm that you're trying to control ahead of the weaning period, you don't have to vaccinate the calves in those first three months of age to mount a successful immune response. They are protected by the vaccine mechanisms provided by the dam.”

This finding is reassuring for farms that rely on frozen colostrum to ensure consistent quality and availability – freezing colostrum preserved the essential protective functions in this study.

Maternal antibodies: Protection and suppression

The study also showed that maternal antibodies protect calves during the first weeks of life, but they can also interfere with the calf’s ability to mount its own immune response. Calves receiving fresh or frozen colostrum were protected by maternal antibodies for about six weeks but did not mount a strong response to vaccination until around three months of age. In contrast, colostrum-deprived calves showed a different pattern and lacked passive protection but were able to respond and mount an immune system response earlier than the calves that received colostrum.

This phenomenon, known as immune interference, means that vaccination strategies for calves must account for maternal antibody dynamics. Dr. Cangiano emphasized that vaccination of the dam during the dry period is essential for ensuring the calf’s early-life protection.

Shaping the immune landscape

The research also explored how colostrum influences immune cell populations in the newborn calf. Gamma-delta T cells, a dominant immune cell type in calves, bridge the innate and adaptive immune systems and play a crucial role in early-life defense.

“In calves, gamma-delta T cells are the most important immune cells in these animals,” he noted. “At this stage, they're one of the few that can respond effectively against similar infections. And they function kind of as a bridge between the innate and the adaptive immune system.”

In colostrum-deprived calves, these cells expanded rapidly in the first 48 hours, likely in response to environmental microbes. Colostrum-fed calves showed a moderated expansion, indicating that colostrum signals help regulate immune activation and prolong the dominance of gamma-delta T cells during the early weeks of life.

Other immune cell populations also displayed distinct patterns depending on whether calves received colostrum. Colostrum-deprived calves showed higher levels of inflammatory macrophages and neutrophils, suggesting that their immune systems were compensating for the lack of maternal immune programming.

Colostrum dampens inflammatory overdrive

Another finding was that colostrum-deprived calves had a hyperactivated innate immune system. Neutrophils were more active and produced more oxidative bursts, reflecting a system working overtime to respond to microbial challenges without regulatory cues.

“The colostrum deprived calves have increases in a lot of artificial activation of their inane immune system, meaning that the immune system is working overtime to compensate for the lack of colostrum. There are more macrophages in circulation, and those macrophages are more active – they're more inflammatory,” he explained.

Dr. Cangiano argued that while this might seem beneficial on the surface, it can lead to dysregulated immune responses. Calves transitioning from a sterile uterus to a microbe-rich environment need to develop tolerance as well as defense. Colostrum plays a key role in this balance by dampening unnecessary inflammation and supporting orderly microbial colonization of the gut.

Microbial colonization and gut development

Colostrum doesn’t just affect immune cells – it shapes the microbial landscape of the calf’s gut. Dr. Cangiano highlighted research showing that colostrum contains specific oligosaccharides that act as prebiotics, selectively feeding beneficial bacteria. These bacteria colonize the gut mucosa, forming a barrier against pathogens and creating a favorable environment for immune development.

“Colostrum also has an effect on how the intestinal microbiome is established. There are specific factors in the colostrum that are called oligosaccharides that are prebiotics that are synthesized by the mammary gland as a neutral source for specific bacteria that can have a lot of beneficial aspects in some of the mechanisms,” he said. “They are on the surface of the mucosa and establish an area that doesn’t allows for pathogens to colonize. Colostrum also has an effect in promoting the cell region of these bacteria.”

In addition, growth factors in colostrum accelerate intestinal maturation, promoting villus growth and epithelial proliferation. This strengthens the physical barrier between the external environment and the immune system, supporting better nutrient absorption and defense.

Processing colostrum matters – but how much?

While freezing colostrum preserved key immune functions in the study, other processing methods like pasteurization, refreezing or spray drying may affect certain bioactive components. Some research has shown that pasteurization can degrade specific immune factors, but the implications for calf immunity remain unclear.

Dr. Cangiano emphasized that more research is needed to understand how different processing methods influence colostrum’s immunological programming effects. As farms adopt various strategies to manage colostrum hygiene and logistics, understanding these effects will become increasingly important.

Practical takeaways for farmers, veterinarians and nutritionists

For dairy producers, veterinarians, and nutritionists, the implications of this research are significant:

• Timely, high-quality colostrum feeding remains essential. The first feeding should deliver 10% of the calf’s body weight, ideally within two hours of birth, followed by a second feeding of 6%.
• Frozen colostrum can be a reliable option when fresh colostrum isn’t available, provided it is handled correctly.
  Maternal vaccination during the dry period is crucial for ensuring calves receive targeted antibody protection through colostrum.
• Early-life vaccination strategies must consider maternal antibody interference, with boosters scheduled after three months for optimal response.
• Colostrum influences more than IgG transfer — it programs the immune system, shapes the microbiome, and modulates inflammatory responses, setting the foundation for lifelong health.

As Dr. Cangiano put it, colostrum is not merely a nutrient source but a biological bridge between the sterile womb and the microbe-rich external world. It provides antibodies, immune cells, growth factors, and microbial “instructions” that together orchestrate a smooth transition for the newborn calf.

More research needed

While the foundational role of colostrum is well understood, Dr. Cangiano highlighted several open questions:

• How do different processing methods affect bioactive components?
• Which specific factors are most critical for immune programming?
• Can targeted supplementation mimic or enhance colostrum’s effects in cases where quality is variable?

Answering these questions will require multidisciplinary collaboration among immunologists, microbiologists and dairy scientists. But for now, Dr. Cangiano’s research reinforces a simple but powerful message: getting colostrum right in the first hours of life pays dividends in calf health, performance and resilience for months to come.