It’s true that your horse cannot get a “cold”/respiratory infection without a virus but all horses carry around a generous supply of both viruses and bacteria. While winter weather can’t cause a respiratory illness, the stress of severe weather coupled with the effect of cold, dry air on the lining of the respiratory tract sets the stage for any waiting viruses or bacteria to take hold by weakening normal immune defenses. Seniors and young horses have an additional risk factor since their immune systems are often not fully competent.
There are a variety of natural and man-made substances which can stimulate various aspects of the immune response but I don’t want to talk about those today. Before they can even be effective the immune system needs to have all the key nutrients it needs to function.
Keeping a horse fleshed out is usually the easiest part of feeding. All it takes is empty calories. An inadequate supply of protein in general or specific amino acids can greatly reduce the strength of immune system reactions. Everything from the multiplication of immune system cells to antibody, cytokine, even mucus production requires adequate protein and B vitamins. Pregnant, nursing, growing and debilitated animals have highest needs. If there is any question of adequate protein, switch from plain vitamin and mineral supplementation to one that includes 20+% protein from vegetable sources and whey for the best amino acid array.
Bio-active whey protein is also potent support for glutathione, the major antioxidant system in the body. Glutathione provides homeostasis for both immune cells and all body cells against free radicals generated during immune reactions. Colostrum does more than supply antibodies to newborns. It is a specific source of proteins like lactoferrin, complement and proline-rich polypeptides (PEP) as well as cytokines, all of which have immune activity for any age horse.
Essential fatty acids also have profound effects on the immune system. Omega-3s are essential to function of the sophisticated immune system which targets and remembers specific organisms. Omega-6 fatty acids are utilized in reactions involving the primitive immune system which is the first line of defense against invaders. The barrier tissues of skin and mucus membranes are particularly dependent on omega-6.
Fat soluble vitamins A and E require attention. Vitamin A is needed for good immune function in the skin and mucus membranes. E is a well known antioxidant that is particularly critical for the survival of both B and T-cell lymphocytes. These cells have high levels of polyunsaturated fats in their membranes so are especially vulnerable to oxidative damage. All hay based diets are vitamin E deficient. Vitamin A is present in hay as carotene and also loses activity with time.
The immune system can be its own worst enemy because many of the reactions used to defend against invaders involve the generation of high levels of oxidative stress. When this happens, horses can benefit from the addition of plant based antioxidants such as berry powders, Turmeric, bioflavanoids/quercetin, malic acid, N-acetyl cysteine, glutamine, pancrelipase and vitamin C. Also supportive are arabinogalactans, mannanoligosaccharides and fructooligosaccharides which are naturally occurring complex polysaccharides from plants which provide gentle stimulation to the rich supply of immune tissue in the intestinal tract – the GALT (Gut Associated Lymphoid Tissue).
The immune system is complex because it has to be but understanding all the nutritional elements it needs to function well is the cornerstone of immune support.
Eleanor Kellon, VMD