When Pasture is Too Much of a Good Thing - The horse has evolved as a grazing animal, hence, pasture plays a pivotal role in equine nutrition. Reported intakes of fresh pasture by horses can range from 1.5 to 5.2 percent of body weight per day. With such a large intake of pasture possible, can horses overconsume? What components of pasture grass can cause problems if taken in at excessive levels?

Equine Cushing’s Disease, more correctly called Pars Pituitary Intermedia Dysfunction (PPID), is a non-cancerous but progressive enlargement of the pituitary gland in the horse. It is estimated that 20 percent of horses over the age of 15 will develop PPID. Note that Cushing’s Syndrome in humans and dogs (when not due to giving too much steroidal medication) involves an actual tumour of either the pituitary or the adrenal glands, (either benign or malignant), whereas Cushing’s Disease in horses has a different cause.

Horses can develop equine asthma when they’re exposed to airborne organic dust that can found anywhere — in a dirt paddock, on a gravel road, or in an indoor arena. But the most common culprit is dusty, moldy hay. Round bales can be particularly problematic as horses tend to tunnel their muzzles into the bales and inhale dust and mold.

“The stable environment invariably presents challenges of dust, mould and proper ventilation,” says Susan Raymond, instructor of Equine Guelph’s Management of the Equine Environment online course. “Most horses are well equipped for living outdoors and thrive, provided certain provisions are met.” Dr. Raymond completed her PhD in investigating the effects of exposure of horses to mycotoxins. She has also been involved in air quality research, which provided practical recommendations to the horse industry on stable design and management.