Thursday, December 16, 2010

What May Be Floating Around in Your Barn?

Winter brings cold temperatures and inclement weather. We want to keep our horses as comfortable as possible, which to us means keeping them warm and snug indoors when the wind is howling outside. So, we blanket them, put them in a warm stall, close all the doors and windows and feed them extra hay…they will be so warm and happy, won’t they? Well, they may be warm but they may also have trouble breathing.

Barns are often built for warmth and protection more than air flow and ventilation. Measurement of respirable organic particles or particulate matter in horse barns has shown potential danger for horses housed inside. The combination of structural design, hay and bedding stored in or near the barn, tractors and equipment running through from time to time, activities such as sweeping aisles and cleaning stalls, and possibly a connecting indoor arena can result in the level of airborne organic dust reaching damaging levels. Airborne particles in numbers greater than 2.4 mg/cubic meter (M3) of air have been shown to increase the incidence of airway disease in horses. In a study measuring air quality, most horse barns measured 40 – 60 mg/M3. The breathing zone during feeding was often 30 – 40 times higher. Measured particles included dust, endotoxins, mold spores, ammonia and silica from arena dust. Hay has been measured at 19.3 mg/M3, and bedding, especially straw bedding, can be even higher, making hay and bedding major contributors. All these airborne particles can wreak havoc on respiratory function in stabled horses.

Horses have an amazing respiratory system that is exceptionally equipped to function during exercise. Respiration rate (RR) varies dramatically from rest, 10 – 12 breaths per minute (bpm), to intense exercise, where it can increase to 150 – 180 bpm. Tidal volume (TV), the volume of air that is inhaled and exhaled with a normal breath, ranges from 4 – 7 liters per breath at rest. During strenuous exercise TV increases to 10 – 12 liters. Minute volume (MV) is the total volume of air inhaled and exhaled per minute (MV=TV X RR). Horses at rest have MV averaging 100 liters per minute, but during very hard work MV averages an astounding 1500 liters per minute. Even at rest, this is a tremendous amount of air flow into and out of the lungs. When the inhaled air contains high numbers of respirable organic particles, the potential for irritation is high. Add exercise and the increased respiration rate may cause deeper penetration of particulate matter. In addition to air quality concerns, winter also brings frigid air temperature. Research has shown that cold weather exercise can cause asthma-like airway disease in performance horses. Repeated work in cold temperatures can lead to chronic airway inflammation.

Non-infectious respiratory disease with airway inflammation in horses is a common clinical problem when horses are stabled. Some studies suggest that 25 – 80% of stabled horses suffer from Recurrent Airway Obstruction (RAO), commonly known as “heaves”, and Inflammatory Airway Disease (IAD). Horses may suffer from chronic coughing, decreased performance, difficulty breathing and abnormal lung sounds. Signs do not become apparent until a large number of airways are affected, and therefore many more horses may be affected than is realized. Once particulate matter is in the lower airways, the body sees it as foreign material and mounts an immune response. Inflammation is an important immune system weapon but can have negative effects as well. Airway walls thicken, become hypersensitive, spasm and lung function is impaired. Blood oxygenation decreases which causes increased respiratory rate and tidal volume. Most horses with RAO will develop an exaggerated expiratory “push” and a “heave line” which is a ridge of muscle along the lower abdomen that develops when the horse works harder to exhale against collapsing airways.

The most effective treatment for non-infectious respiratory disease is to prevent exposure to respirable organic matter and to limit hard work during extreme cold temperatures. If horses cannot be kept outdoors, then the focus should be on reducing airborne particles in the barn. Improving ventilation and feeding low-dust feed can make a huge difference. Feeding hay in feeders at ground level instead of hay racks above the grain is one step that may help, but hay should be thoroughly soaked in water and fed wet to effectively reduce dust and molds. Affected horses may not show improvement until hay is totally replaced by feeding a complete feed with hay built in. Purina Omolene 400 and Equine Senior are low-dust feeds containing quality fiber sources to replace hay. Many horses with RAO or IAD cannot tolerate any hay, even wet hay, and do much better eating one of these products. Keep in mind that horses eating hay in adjoining stalls can still cause problems for affected horses.

Any time you notice coughing or labored breathing in your horse, make an appointment with your veterinarian for a thorough exam to determine the cause and the appropriate course of action to provide relief.

No comments:

Post a Comment