Stresses such as chronic pain, long-distance travel, or environmental changes can compromise the immunity of your horse. . Allergies, heaves, thrush, insect bite reactions, and hives all can reflect a struggling immune system, as can the more obvious signs of respiratory disease.
Healthy, well-managed pastures supply your horse with many important nutrients, including vitamins E, A (as beta carotene), and C. Grasses are also high in omega-3 fatty acids in the proper proportion to omega-6s. And if a variety of grasses and clover grow in your pasture, you can expect the protein quality to be good.
While free access to pasture often provides most of the nutrients your horse requires to remain healthy, many horses rely on hay as their main forage source. Hay loses some of its vitamins and omega-3s in storage, so horses consuming only hay for prolonged periods of time (more than three or four months without fresh pasture) might require additional feed supplementation. If your horse exhibits signs of suppressed immune function (e.g., signs of respiratory infections including a runny nose, coughing, and fever; recurrent thrush; bacterial infections; fever; allergic reactions; and general malaise), it’s time to boost his diet’s nutrient content. One of the immune products I use (going on 12 years with spectacular results) is Transfer Factor. You can read more about it on my blog.
Your horse might also need Vitamin E to fill nutritional gaps and maintain a healthy immune system:
Vitamin E is a powerful antioxidant. Antioxidants protect against disease by neutralizing the damaging free radicals (unstable molecules with an unpaired electron that pull electrons from other molecules) that mental and physical stress produce.
Vitamin A and C are also important for immune function. Vitamin C has been shown to be an effective supplement in reducing the effects of stressful travel.
Omega-3 fatty acids have been shown to reduce inflammation as well as allergic inflammatory response in other species. Researchers at the University of Guelph’s Equine Research Centre found evidence that the fatty acid source flax seed can potentially reduce the allergic inflammatory response in horses susceptible to biting midges. Omega-6 fatty acids can exacerbate inflammatory responses if fed in large amounts, but omega-3s do just the opposite–they help inflammation subside. I keep a coffee grinder in the barn to grind flax seed fresh daily.
Spirulina Blue/green algae reportedly reduces allergy signs and improves respiratory function in animals.
Massage is another way to reduce stress in the performance horse. At horse shows, sports massage can make the difference between a nervous, uptight horse and a relaxed happy performer.