The Respiratory Challenges Of Equine Performance

Improving the horse's ability to breathe ensures more efficient production of ATP, the fundamental energy molecule of the body. Aerobic metabolism (when the horse is absorbing sufficient oxygen) produces approximately 10 times more ATP than anaerobic metabolism (when oxygen supplies are inadequate to meet demand). By selecting focused nutritional support and an effective training program, you can make a substantial improvement in your horses' respiratory efficiency. There are also important steps to take in daily management that can have a major impact on respiratory health. Here are the ones we have found to be most important. Although some of these risk factors can be reduced with nutritional support, all of them should be addressed in the management program.

1. Airborne particles - dust, soot, mold spores, grain and hay dust. All create inflammatory response, which decreases airway function. Particles lead to: a) excessive mucus secretion, b) susceptibility to infection of inflamed tissues, c) bronchial constriction, d) formation of cyst-like structures to isolate and reduce irritation, thus reducing respiratory efficiency of the local tissue.

• Keep shedrows, stable and paddock areas as dust-free as possible; wet down frequently, consider alternative surfaces.
• Maintain optimum ventilation in all enclosed areas.
• Eliminate all feedstuffs of questionable quality; allow no feed that appears dusty or that may contain molds.
• Consider alternative sources of roughage in the diet, to reduce or replace hay. For example, some feed manufacturers offer formulas that supply high roughage levels (usually with beet pulp) so you can reduce the amount of hay you feed.
• Substitute dust-free wood shavings for straw as bedding material.

2. Ammonia - highly irritating fumes from horse's urine. High ammonia levels in stalls lead to inflammatory response and damage the respiratory epithelium.

• Muck-out stalls as frequently as possible.
• Make sure bedding is deep enough to efficiently absorb urine.
• Insure that ventilation system is efficiently exchanging air at a level at least as low as that of the horse=s head.
• Consider crude protein levels versus protein quality (amino acid balance). Excessive crude protein will create significantly higher ammonia levels in urine. Improve protein quality.

3. Ozone and other gas pollutants - ozone (O₃) is a highly unstable, reactive oxygen form that is an increasing pollution problem in metropolitan areas. It is highly irritating to mucus membranes and a very potent generator of free radicals. Leads to inflammatory response and cell wall damage. Other gas pollutants causing similar problems include aromatic hydrocarbons, sulfur dioxide, etc.

• The location of the stables is the main factor in the severity of this problem. Make sure ventilation system does not make this problem worse.

4. Feed contaminants - mycotoxins (aflatoxin, zearalenone, trichothecene, etc.) endophyte and other fungi infestations of grain and hay. All are known to be destructive to cell membranes, reduce growth, and can be insidious (result in subclinical problems) in low contamination levels. Mycotoxins are most commonly found in grains. Endophyte infests fescue (grass hay/forage).

• Request that your feed dealer verify that all feeds are free of these contaminants. A fluorescence assay is used to identify mycotoxins, which typically are not visible to the naked eye.
• Identify forage and hay grasses and have any fescue checked for endophyte contamination. Although reports of problems from endophyte contamination have focused on gestational disorders, endophyte reduces performance in all horses.

5. History of respiratory infections - Many veterinarians have noted a propensity for bleeding problems and other respiratory disorders in horses who suffered significant respiratory infections as juveniles. Pulmonary or bronchial lesions may be formed which may be "weak spots" in the future. Such horses should be considered to be at higher risk of respiratory disorders during their performance careers.

• Maintain extra vigilance in following these guidelines for horses with this type of history.
• If respiratory infection is suspected, suspend high- intensity exercise immediately until the horse receives a clean bill of health.

6. Anemia - low red blood cell (erythrocyte) count and/or low hemoglobin level. Although there are several possible causes of anemia, the two most common causes are diet and EIPH (exercise induced pulmonary hemorrhage, or bleeding). Anemia lowers the capacity of blood to carry oxygen and carbon dioxide. This in turn makes higher demands on the cardio-pulmonary system; higher blood pressure and heart and breathing rates, leading to greater mechanical challenge to the pulmonary capillary beds. Anemia is also likely to be accompanied by decreased deformability of the red blood cells. Red blood cell deformability is essential for efficient flow through the capillaries and minimum abrasion of capillary walls.

• Insure adequate nutrition for red blood cell and hemoglobin production.
• Make sure that non-nutritional anemia is not present. Consult your veterinarian.