Transfer Factor: An Answer To Treatment and Prevention of Equine Disease?

by Heather Smith Thomas

For many decades, the typical way veterinarians and horse owners have dealt with disease is by vaccination and by treating sick animals with anti-microbial drugs when signs of illness appear.

By the time the animal shows symptoms, however, damage has already occurred and it can be more difficult to treat the disease. In some instances, irreversible damage has already been done. The use of pathogen-killing drugs is not always as effective as we’d like, and today this use is also being questioned due to the increasing development of drug-resistant pathogens. This microbial resistance diminishes the effectiveness and benefit of some of the drugs we’ve come to rely on.

Horse owners are beginning to look at alternatives to antimicrobial use in dealing with disease. A bright spot in this quest is the use of immune system enhancement and the role of transfer factors. If the immune status of our animals could be enhanced, disease would be less likely to occur, and even if the animals do get sick, the severity and duration of disease could be reduced and they would recover quicker without the need for as much antimicrobial treatment.

Dr. Steve Slagle, a veterinarian in Granite Bay, California, near Sacramento, has been working with a fascinating product that is now available for humans and animals. “The product that I’m using in my practice is a natural immune enhancer and modulator. It derives its efficacy from a protein produced by the immune system’s master immune cells called T lymphocytes. The protein is called transfer factor, and it is also found in cow colostrum. If you buy a bag of dried colostrum (a substitute colostrum product for newborn calves) at the feed store or veterinary supply, about 1% of that product is this protein. We extract that 1% from cow colostrum which enables us to deliver very high levels of transfer factor in our products,” he explains.

“The transfer factors were originally marketed as a human product. I started using them in my veterinary practice in February 1999. So many veterinarians were using the human product that 4Life Research decided to create a veterinary product line for dogs, cats, horses and newborn livestock. Dr. Joe Ramaekers, a colleague of mine, was asked to formulate the product line. Dr. Ramaekers then went on to develop a cancer product for dogs and cats, and a formulation for ruminating livestock,” says Slagle.

“I have been practicing veterinary medicine since 1968 and I have never seen anything that is as exciting as this. I must admit that when I was first informed about transfer factor by a longtime friend, a small animal veterinarian, I was skeptical. He claimed success on so many different types of cases. This didn’t really make sense or seem feasible until I realized some time later that the transfer factors were not treating the particular condition. They were simply enabling the immune system to do its job,” says Slagle

“During the first month I tried it, I used transfer factor on three foals. All three cases were critical and I felt their chances for recovery were slim. The first one was a severe pneumonia. The second was a joint ill infection involving the hock. The third was a terminal septicemia. All three made dramatic recoveries, so I was more than impressed. I was amazed,” he says.


“The two products from 4Life Research that I use most often in my equine practice are Equine Performance & Show (patented for tumors, EPM, Cushing’s and several other diseases) and Animal Stress Pack (for treating acute conditions). Equine Performance & Show is used primarily as a complete high-end daily supplement with maintenance levels of transfer factor and other immune-enhancing ingredients. I also use it on my chronic cases like tumors, Cushing’s, allergies, and autoimmune diseases like pemphigus (a chronic skin disease). Animal Stress Pack is my emergency treatment, with high levels of transfer factor and other immune enhancers, probiotics, electrolytes and stress vitamins,” says Slagle.

“One of our first studies in horses was done at a major Quarter Horse ranch in Texas that was fighting a losing battle against strangles and a rhodococcus outbreak in which they had already lost several very valuable foals. We put the remaining affected foals on Animal Stress Pack and turned the tide on this very serious situation. All of my infectious disease cases receive the Stress Pack. Even though it is not treating any particular disease, we are dramatically improving the immune response, giving the immune system—which is the ultimate disease fighter—the tools it needs to finish the job,” he explains.

This product is patented for use in horses with EPM. At the latest AAEP Convention in Anaheim, California, Slagle met with Dr. Thomas Bello (a research veterinarian with a private practice, Sandhill Equine Center, in North Carolina). Bello had earlier done the clinical trials for a major drug company on their product for treating EPM.

“The literature on EPM treatments had shown that only between 10% to 20% of horses experience full recovery, returning to their original performance levels. Dr. Bello then became interested in our product and began using it for treating horses with EPM, and getting great results,” says Slagle.

“Dr. Bello then presented a paper at the AVMA convention, which was later published in the Journal of Equine Veterinary Science in 2008—showing that 28 performance horses with EPM were treated with the new EPM product along with the two transfer factor products. At the time of publishing, 82% of those horses were in full recovery. In our recent conversation at the AAEP convention, Dr. Bello told me he now has more than 50 cases in the study, and a recovery rate of over 90%. Apparently the additional immune support was what was needed to bring full recovery. It is also very common to see a relapse in horses that are only being treated with antimicrobials, but Dr. Bello indicated that with his regimen he has not experienced this problem,” says Slagle.

“Since transfer factors are true modulators, my allergic and autoimmune patients go on a daily regimen of transfer factor. Somehow this protein is able to re-educate a confused immune system and bring relief to a large percentage of my equine patients. I generally start them on Performance & Show, along with a week or two of the Stress Pack to front-load the system with high levels of transfer factor. Then when symptoms are under control, we continue with only the Performance & Show,” he explains.

The immune system provides the body with the ability to recognize and remember harmful invaders (pathogenic bacteria, viruses and fungi). Suppressed or damaged immune systems can have disastrous results. One of the most devastating examples is SCID (a genetic defect that occurs in some Arabian foals). They are born without a functioning immune system. After the temporary immunity from the dam’s colostrum is gone, these foals always die of disease.

A healthy immune system has the ability to remember and recognize pathogens, mounting a defense against them. Disease occurs in humans and animals when the immune system is overwhelmed by the pathogen.


The body’s immune system produces memory molecules whenever it is exposed to disease or receives a vaccination. These memory molecules are bioactive peptides. An example is the “immune” factor passed from a mare to her foal or a cow to her calf via colostrum. This transfer is critical in helping the immune response cells (antibodies) with identification and activation. They are what we might call super boosters in immunity.

Transfer factors were discovered in 1949. Earlier, it had been noticed that immunities could be transferred from one person to another by blood transfusions. In 1949, Dr. H. Sherwood Lawrence, a researcher working on the problem of tuberculosis in humans, found that he could transfer immunity to his patients by using dialyzed leukocytes. When this extract was taken from a blood donor who was resistant to the pathogen and injected into a patient that had no immunity, the immunity of the donor was transferred to the naïve patient. A portion of the lymphocyte (white blood cell) contained what Lawrence dubbed “transfer factor”.

Research was conducted in more than 60 countries (and more than 3500 studies were done) during the 1950s through 1970s and then practically halted. At that point in time, the world’s blood supply was becoming contaminated by HIV and hepatitis C virus and the only known source of transfer factor was blood. Research on this phenomenon was also put on hold because more exciting discoveries revolved around antimicrobial drugs. These were the promising wave of the future that could halt diseases in their tracks. Use of transfer factor was very limited for awhile—especially in veterinary medicine—because it was more expensive to produce than antibiotics. Research did continue, but slowly.

The phenomenon of transfer factor was not actively pursued until the late 1980s when it was discovered that bovine colostrum contains significant amounts of this ingredient that stimulates both aspects of the immune system (humoral and cellular immunity). Veterinary researchers observed a large number of lymphocytic cells in the normal mammary gland secretions of cows, and wondered what role they might play in the health of the newborn calf, realizing that colostrum does more than merely provide passive immune protection. We now know that transfer factor is a lymphokine—one of the protein messengers released by antigen-sensitized lymphocytes (white blood cells).

Chicken eggs also contain transfer factors, and the combination derived from eggs and colostrum increases the effectiveness by 185%. Transfer factors from cow colostrum and eggs are superior to and more functional than transfer factors from humans because animals are exposed to many more species and types of bacteria, viruses and fungi.

As stated by Dr. Richard H. Bennett (Infectious Disease Microbiologist and Immunologist, and former consultant to the National Research Council), transfer factor is one of the most potent messengers in the body and has three effects on the immune system. These are called inducer fractions, antigen specific fractions, and suppressor fractions.

Inducer fractions – One of the functions of transfer factor molecules is to selectively enhance immune surveillance by helping the body recognize various antigens. This selective immune surveillance is made possible by the inducer fractions. One of the veterinarians who consulted with the company that has the patent for extracting transfer factor from colostrum stated that one capsule (200 mg) of transfer factor has the capability of recognizing more than 100,000 different pathogens. Not only can transfer factor be specific for an individual antigen that a lymphocyte might be exposed to, but it can also stimulate a multiple response and provide protection against several strains of that organism.

This enhancement is made possible by the inducer fraction that acts on what are called the Natural Killer (NK) Cells, according to Bennett. The NK cell’s job is to seek out any cells that have been altered by microbes and destroy them. They have a similar protective role in preventing the formation of malignant tumors. The inducer fractions also influence the body’s overall response by increasing the function of the T helper lymphocytes which play a critical role in a balanced immune response to resolve most infections, says Bennett.

The researchers found that they could expose the cow to various bacteria and viruses, and the cow would then produce transfer factor that could stimulate immunity not only to those pathogens but also to other related strains that are much more pathogenic to other species. This is of benefit when using transfer factor to aid disease resistance in horses, for instance. Cows can produce large quantities of colostrum that can then be used for extracting transfer factor that can benefit other species—since transfer factor in horses, cats, dogs, humans and cows has similar structure and identical function.

Another exciting aspect of transfer factor is how quickly the protection is mounted. Immunity from vaccination generally takes 10 to 14 days to develop, whereas transfer factor activates immunity in less than 24 hours.

Antigen specific fractions – Transfer factors act in two ways to “educate” the immune system to respond quickly when confronted by disease threat. One is a response to a specific pathogen such as a cryptosporidium protozoan that might be common to several species, and the other response is to similar pathogens—such as herpes virus infections that differ from one host species to another. Thus transfer factors can “educate” the immune system to recognize and fight a wide array of related, but not identical, infectious agents, according to Bennett.

Suppressor fractions – In every physiological system in the body there are checks and balances, so transfer factor can also act to suppress immune function when necessary. The process of achieving balance is called homeostasis. Once a disease threat has been confronted, and a sufficient response has occurred to thwart it, the body must down-regulate the battle so the immune system can return to a resting state and conserve its resources for the next challenge.

The suppressor fractions signal the T helper lymphocytes and the cytotoxic T cells to slow down their activity and return to a quieter state. This “quieting down” the immune response is important because some pathogenic microbes can hide in certain body tissues and the immune response becomes directed toward those tissues, leading to autoimmune diseases. The suppressor fractions of transfer factor appear to be the way the body limits overzealous immune responses, according to Bennett, and becomes the body’s means to protect itself from an inappropriate immune response.

It seems paradoxical that the transfer factor can both stimulate and suppress immune function, but this is part of its important role. Thus it can prevent autoimmune diseases, and other situations where the body’s own immune response has over-responded to antigens, such as allergic reactions and COPD.


Stressed animals generally become more vulnerable to disease because stress (and the resultant rise in cortisol levels) hinders the immune system. Slagle and Ramaekers tested the transfer factor product on stressed calves to see if it controlled cortisol levels. “We have done two controlled studies on stress and cortisol levels of stressed calves entering the feedlot. One was in Tiffin, Ohio at a private, veterinary-owned and operated feedlot. We repeated that study at Texas A&M. Our results were basically the same. We took blood samples twice daily for 12 days and saw a 46% reduction in cortisol levels in the calves that received transfer factor, with a large decrease in treatments, along with better weight gains,” says Slagle.

“We have not repeated that kind of study in horses, but with the responses (reduced incidence of disease in stress situations) we see in horses, I feel the results would be similar,” he says.

The use of transfer factor to stimulate the body to mount a better immune response to pathogens can reduce the need for antimicrobial drugs. This can help retain their effectiveness longer, since over-use of these drugs has led to increasing numbers of resistant pathogens. We need to find ways to maintain their effectiveness as long as possible.

Transfer factor can boost immunity within a few hours. This makes it very beneficial for use in newborn foals, horses that will be transported, or even as a post-exposure treatment when you know a horse has come into contact with disease agents. Veterinarians have also been using transfer factor to help horses deal with frustrating problems like Cushing’s, laminitis, colitis, cancers, allergies, chronic metritis, EPM, pigeon fever, scours, strangles, and many viral diseases. Helping the immune system help itself is the promising wave of the future.

For more information, Dr. Steve Slagle can be reached in Granite Bay, California at 916-791-2911 or Dr. Joe Ramaekers at 831-476-5050 or check his website:

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