Feeds and Feeding the Horse
Roughages are important in your horse’s diet to help prevent colic and other health issues. In addition, roughage is high in calcium which helps maintain your horse’s calcium to phosphorus ratio and leads to healthy bones. Two types of roughages are legumes and grasses. Legumes contain more protein and minerals and are more palatable to the horse, meaning she is more likely to want to eat. However, you must be especially vigilant with legumes to ensure they are not dusty or moldy. Examples of legumes include alfalfa and clover. Grasses hold fewer of the essential nutrients found in legumes, but are less likely to be moldy. Examples include timothy, prairie grass, and orchard grass. To maintain your horse’s health, you want to be sure to feed your horse high quality roughages that are free of dust and mold.
Mold + Mycotoxins
You can determine if your hay has mold by checking it thoroughly: look for visible signs of discoloration and spores, feel for dampness, and smell for freshness.[i] During the hay harvesting process it is important for the crop to dry thoroughly. Wet seasons or high humidity will prevent the hay from drying properly. When moisture levels are above 14-15% mold and bacteria will grow on hay[ii] which leads to the production of mycotoxins.
Mycotoxins are the toxic chemicals produced by the bacteria, mold, or fungus growing in high moisture hay. These toxins have been linked to health conditions such as colic, neurological disorders, paralysis, hypersensitivity, and brain lesions.[iii]
In order to prevent bacteria growth some hay growers apply preservatives. The most common preservatives are composed of organic acids that are similar to those found in a horse’s digestive system.[iv] A one-month study at the University of Illinois compared yearlings fed exclusively on treated hay to those fed on untreated hay and found they consumed the same quantity of hay and gained the same amount of weight. A study at Cornell University tested the palatability of treated hay by offering both treated and untreated hay. This study found that horses do prefer untreated hay when given the option but were not unwilling to eat treated hay when it was the only option.
Dr. Claire Thunes of Summit Equine Nutrition explains that while the thought of feeding an acid generally raises concerns about gastric ulcers, the propionic acid used as hay preservative is buffered to neutralize its acidity making it a similar pH to tap water.[v] Thunes goes on to say, “if the hay is clean, smells good, has good color, and is palatable, there’s no reason to avoid it just because it’s been treated with propionic acid.”