The Coronavirus pandemic brought to the forefront awareness of epidemiological facts about how a virus is spread and tactical methods to curtail transmission. With this degree of knowledge, horse owners have a better understanding about respiratory disease protection today than in any time in history. In collaboration with your veterinarian, you can implement strategies to optimize your horse’s respiratory health.
Insults on Airway Tissue
A starting point to protect a horse’s respiratory tract is to improve environmental issues that assault equine airways. Main causes of airway dysfunction result from exposure to particles of solid or liquid droplets suspended in air. There are many such substances: a) Inorganic materials like silica, metals, and diesel discharge from tractors and vehicles; b) Organic debris from bacterial products, animal waste, molds, spores, pollens, insect parts, and wildfires; and c) Endotoxin (the cell wall of Gram-negative bacteria) present in manure and particle dust.
Horses obviously can’t wear face masks so strategies for airway protection rely on human intervention to minimize circulating particulates in the air. Particulates range from coarse (10 microns) to fine (2.5 microns) in size. To give you a reference point, a human hair is 60 – 70 microns thick. Particles of 5 – 10 microns that make it past nasal hairs and sneezing get through to irritate nasal and throat tissues. Coughing and the mucociliary escalator in the lining of the respiratory tract eliminate particles up to 30 microns but those that aren’t cleared can settle in lower airways, with particles less than 4 microns ending up in alveoli (air-filled sacs in the bottom reaches of the lungs).
An indoor and stall environment have a huge impact on health of the respiratory tract. One study identified that 55 % of previously healthy Thoroughbred horses 16 – 24 months of age developed inflammatory airway disease within three days of arrival at a training barn; by 28 days, only two of 20 horses remained free of airway inflammation. Dusty environments tend to increase airway mucus, which impairs performance.
Mitigating the Impact of Feed Materials
Particulate levels are high indoors especially during feeding and stall cleaning. This is exacerbated when a barn is closed up in winter. Consumption of dry hay is known to increase dust by 30 to 40 times in the breathing zone air around a horse’s nose. Clean hay creates 19.3 µg/m3 (cubic meters of air) respirable dust in the breathing zone while dusty hay puts out 81 µg/m3 of respirable particles.
Square or round bales increase airway inflammation compared to pasture. Hay nets and hay racks at head height increase particulate intake compared to feeding on the ground. Horses living outdoors are exposed to relatively small amounts of particulates even when fed the same hay as stabled horses. Although a high-forage diet contributes to equine gastrointestinal health, hay as a source of dust, mold, and particulates contributes to airway inflammation. Lower-dust feed, like pellets, quality hay cubes, baked or chopped hay, or fermented haylage greatly reduce dust levels throughout a stall environment.
Mitigating the Impact of Feces and Urine
One critical substance that generates respiratory inflammation is endotoxin, a component of the bacterial cell wall of Gram-negative bacteria found in large quantities in fecal matter, hay, straw, and even in horse dander. Endotoxin adheres well to airborne particles. Frequent stall cleaning helps to mitigate levels of endotoxin. Soaking or steaming hay further minimizes dust and respiratory irritants. Offer only as…
