If your horse’s immune system functioned perfectly, we’d have no need for antibiotics or vaccinations. Unfortunately, this is not the case. Genetic factors and daily stresses — such as injury, growth, exercise and involvement with other horses — affect your horse’s ability to resist infection.
We can be intelligent about avoiding overstressing or deliberate exposure to other ill animals, but the bottom line is the immune system of even the most carefully managed horse has plenty to do. Enhancing its power is the best we can do to help.
Nutrition And Immunity
Calories: An undernourished horse, receiving inadequate calories to maintain a healthy weight, will have depressed immunity. This shows up as skin infections and/or a heavy internal parasite burden, partially because the key nutrients needed to maintain the integrity of skin and lining of the gut are inadequate.
Protein: An adequate supply of protein is also important. Specific amino acids, notably arginine and glutamine, are needed in amounts that exceed the body’s ability to synthesize them during periods of immune stress.
Vitamins and Minerals: Deficiencies of the fat-soluble and antioxidant vitamins E and A clearly decrease the immune response. Vitamin C’s antioxidant function works to prevent the body’s own cells from being damaged by “friendly fire.”
Adequate B-vitamin status is important for mounting an antibody response to vaccinations or infections. B6 in particular has been shown to be important to all branches of the immune system. Deficiencies of B vitamins impair the immune response, but megadoses do not enhance it. Deficiencies are most likely in young, older or stressed animals (includes heavy exercise/training) and in those with any type of intestinal/digestive problems.
Vaccines and immune-stimulating injectable drugs are the most familiar ways of stimulating the immune system. However, certain herbs have clear immune stimulating effects as well. There are also supplements that concentrate the immune-beneficial proteins found in milk and egg. Even certain strains of bacteria can strengthen local immunity in the gut and body-wide immunity.
We undertook a 10-week feeding trial of immune supplement products, conducted at a busy racing/training stable with a large number of young horses in training. As always, this was a field trial with products used in real barns and under real conditions, not a scientific study. However, we were careful to avoid introducing factors that could directly affect the outcome.
All horses had been residents for at least four weeks, allowing them to acclimate to their surroundings and diet. No vaccinations were given during or for four weeks preceding the trial. No trial horses were shipped off the premises during the study (although there was movement of other horses in the barns). Supplemented and unsupplemented horses were matched by age group (under two years, two- to three-year-olds or four- to seven-year-olds).
Diets used during the trial were started four weeks in advance of any supplements. Horses not in work were fed at 1.75% to 2% of body weight. Horses in training (moderate work level) were fed at 2.25% of body weight. Unsupplemented test horses received 14% protein (all vegetable sources) commercial sweet feed, mixed hay, some on joint nutraceuticals and occasional electrolytes, but no other supplements.
All supplemented test horses also received supplemental antioxidant vitamins and minerals (Vita-Key Antioxidant Concentrate). This was done to ensure no deficiencies of key vitamins or trace minerals that could make the immune stimulating supplements less effective.
About 2.5 weeks into the supplementation period, the farm was hit by an outbreak of flu-like respiratory disease. Unfortunately, many of the products tested reported 30 days supplementation was required to reach full effect, making interpretation of results somewhat difficult. Despite this, there were measurable differences seen between supplemented and unsupplemented horses.
There were 35 unsupplemented horses. All two- and three-year-olds developed the respiratory disease with fevers (up to 104?°), depressed appetite for three to five days and took two to three weeks for symptoms to disappear, particularly coughing, despite treatment with antibiotics in several cases. Change in nasal discharge from clear to white/yellow pus was common in this group. Seven of the 35, all two-year-olds, had coughs that persisted beyond the three-week mark.
Antioxidant Supplement Only
Three horses were supplemented with antioxidants only. All developed the disease, with high fevers for two to three days but with appetites returning after 24 to 36 hours. Nasal discharge remained clear in two of the three. A third required antibiotics after the discharge changed to yellowish. All three recovered completely in 10 days.
Antioxidant Supplement plus 50 grams/day of whey protein Stack (Champion Nutrition)
This group had their protein intake supplemented with highly bioavailable whey protein in addition to the vegetable protein sources. Raw whey protein has been shown to contain a variety of immune-stimulating proteins including lactoferrin, lactalbumin and others.
We had no way of knowing if this product (marketed as a muscle-building aid for humans) contained these proteins, or in what amount, but chose it because it was low-heat processed, maintaining the natural protein forms, as a high-quality protein source. Both horses in this group developed the respiratory disease with high fevers, but temperatures returned to normal by the 36-hour mark. No significant appetite loss was noted and nasal discharges remained clear. Cough lasted eight days in one horse; 10 in the other.
Antioxidants and Actimune (ActiVet Bio Ltd)
Actimune contains IgY, immuno-proteins harvested from eggs of chickens immunized with some common equine pathogens that provide both local passive protection and also stimulate the immune system. Another key ingredient is a patented form of the bacteria Lactobacillus, which binds to harmful bacteria, neutralizes toxins, protects the gut wall and stimulates the immune response. Also included are live yeast cultures, fermentation products from beneficial bacteria, vitamins and minerals.
The two horses receiving Actimune were the only two who didn’t become ill during this outbreak of disease. However, they were also the only two not being actively worked at the time of the outbreak. One was a yearling and the other a three-year-old sidelined two weeks after the start of the study with a foot abscess. It is virtually impossible to say how much the stress of training influenced disease susceptibility in the other supplemented horses, compared to what was almost certainly a greater vulnerability in the weanling (the highest risk group for infectious disease) and stress caused by the foot abscess. Four of the 35 unsupplemented horses were not being actively trained but all developed the infection.
Actimune is currently under university study. Its effectiveness in other livestock is already well documented. Positive field trial results, including veterinarian supervised findings, are available regarding success with problems like chronic follicular pharyngitis in young horses.
Antioxidants and GlutaSyn (Vita-Flex)
GlutaSyn is an extract of “milk serum,” the protein-rich material left over after the manufacture of cheese, which is also the source of whey protein extracts. A patented manufacturing process protects the delicate protein bonds found in the native milk serum, retaining their full biological activity. Central to its activity is the presence of gamma-glutamyl-cysteine and other glutathione precursors, which maintain the integrity of the antioxidant enzyme glutathione reductase and allow white blood cells to achieve maximal activity without undergoin g damage from oxygen free radicals. This unique extract has been granted nine patents for use as an immune stimulant, including one for “mammals” which, of course, includes horses.
Apperon, Inc., the manufacturer of GlutaSyn (sold under Vita-Flex’s label in the USA), is a Nutraceutical Alliance partner (see editorial) and funded a study on GlutaSyn in horses. However, the study results were not published and details kept confidential, according to Peter Kaufman, president of Apperon. This decision was apparently based on unspecified complications with four horses being excused from the study, resulting in a small sample size.
Two horses in our field test — both two-year-olds — were supplemented with GlutaSyn. One of these was a filly who had been suffering from a chronic cough for several months, but she had no evidence of active infection by white blood cell counts and no fever. The cough disappeared within a week of starting supplementation.
Both horses also developed the respiratory disease, with temperatures of 103?° and 104.5?°, but showed minimal appetite suppression and appeared bright despite the fevers. Fevers resolved quickly (24 to 36 hours) and all symptoms, including cough, resolved in seven to 10 days without need for additional therapy.
However, the “chronic-cough” filly began coughing when her dosage was cut from the “loading dose” of two scoops/day back to one scoop/day. This was done at five weeks, somewhat later than the usually recommended time of four weeks into supplementation, because of the recent respiratory infection (supplementation cut back seven days after all signs of infection had resolved). Increasing the dose again to two scoops per day again resolved the cough within a week. Vita-Flex concurred that horses under multiple stresses or with other medical problems may need higher than the recommended dose.
Dosage recommendations were reportedly based on equine studies conducted by the developer. However, they declined to release any details of those studies, claiming they were proprietary.
Antioxidants and Immune One (Source One Naturals)
This pelleted supplement is substituted for part of the grain ration (1 lb. per day per 400 lbs. of body weight). It combines a base of high-quality feed ingredients (barley, barley malt sprouts, alfalfa meal, brewer’s dried grains) with vitamins, minerals and the immune-activating component, larch arabinogalactan (LA).
LA is a complex sugar, too complex to be used by the body as an energy source. Instead, it nourishes the growth of beneficial bacterial forms in the intestine and serves as an immune stimulant. The immune-stimulating properties are probably related to the close structural similarity between this substance and portions of the cell wall of bacteria.
The barley malt sprouts are also high in anti-inflammatory enzymes and the larch itself possesses anti-inflammatory actions. The immune system effects of larch have been well documented in laboratory studies. This product was developed and studied using extensive field trials in horses in California, conducted under direct veterinary supervision. One horse on this supplement had to be dropped from the study. The other did develop the respiratory disease but also showed rapid resolution of fever (two days), preserved appetite despite high fever (104?°), and symptoms resolved in eight days.
The major ingredients in herbal immune-boosting products have been proven in scientific studies to have clear cut activity on various parts of the immune response. There is no reason to think they would work differently in horses, although details of safety and dosage need to be worked out.
We field-tested the rapidly acting herbal immune-stimulant products in a group of horses showing early symptoms of respiratory infection. A virus was making its way from barn to barn, causing dry coughs, low grade fevers in about 70% of affected horses and frothy white nasal discharge. Six horses, between the ages of two and five years, were involved.
We used Equinacea, Herbal-Mune Plus, Immuboost and ImmunoBoost on four and left two untreated. Herbal Plex was not tested, as the formula is identical to Herbal-Mune Plus. Higher recommended dosages were used. Both groups contained one two-year-old. All four treated horses had a white/frothy nasal discharge, one had a temperature of 101.5?° and one had a spontaneous dry cough.
Both untreated horses had the same nasal discharge, neither coughing or running fevers at the start of the test. Symptoms had been present for 24 to 36 hours. All horses were continued in light work.
By 48 hours after starting treatment, all symptoms in the herbal supplement group had disappeared. Of the untreated horses, one still had the nasal discharge and seemed to tire more easily with exercise and the other (the two-year-old) had developed a fever (101.8?°) and cough.
All treated horses continued in their training schedules without problem. The unsupplemented two-year-old had to be stall rested as exercise greatly aggravated the cough.
This was a fairly mild respiratory virus, and responses might not have been as good if the horses were being challenged by a virulent flu, but nonetheless we were impressed, especially since supplementation was not started until after early symptoms had begun to appear.
The horses in our trial receiving only enhanced nutritional support (antioxidants alone or antioxidants plus high-quality protein), showed milder symptoms, fewer complications and more rapid recovery. These results reinforce our continual recommendation that antioxidants and a high-quality diet are of particular importance to horses under stress.
Echinacea-based products also showed a clear benefit, although the virus challenging this group was not as severe.
Those receiving specific immune-stimulating products showed a tendency toward an even greater reduction in the severity of disease. Only Actimune provided full protection compared to the untreated horses matched for age and level of stress. However, the stressors those horses were under were different from those receiving the other products, and the other products might have needed more time to reach their full effect.
It appears from our findings, and available solid research, that commercial immune-stimulating products do affect the immune system and may be worth the money for horses in stressful situations, heavy training or areas with high incidence of diseases such as Lyme, EPM, Potomac horse fever and so on.
Also With This Article
Click here to view "New Infections: Why'"
Click here to view "The Internal War: Barbarians And Sharp Shooters."
Click here to view "Suggested Intake Of Vitamins And Minerals For Peak Immunity."
Click here to view "Herbal Immune-Enhancing Products Ingredients."
Click here to view "Immune-Enhancing Product Ingredients."
Click here to view "Immune Stimulants And Safety."
Click here to view "MSM To The Rescue."