Corn's A-maize-ing Story
The word 'corn' in its original sense meant 'grain'. Corn is more correctly called maize, from Zea mays, Zea being the genus derived from the Greek word for grain or cereal, and mays stems from the aboriginal "maiz", meaning that which sustains life. Maize was cultivated as the very basis of life by the Indians of North, Central, and South America. Corn, unable to disperse its own seeds, is dependent upon man to perpetuate it. And man does just that. Corn is the leading crop in the United States overall as a livestock feed. It constitutes more than 80% of the grain fed to animals in North America, and its production is continually on the rise.
Interestingly, corn is botanically a grass, of the family Graminae, which includes such plants as oats, rye, barley, rice, bamboo, and sugarcane. Wild, annual grasses that grow over much of Mexico and Guatemala, called teosintes, are corn's closest relatives.
Corn, a good-quality and nutritious grain, is an excellent feed for horses, and probably their second-most familiar grain. Many horses find it as palatable as oats, and more tasty than many other cereal grains. Because corn is essentially a hull-less grain, however, it is very high in starches and low in fiber (about 2.2% of its total composition). Corn's digestible energy value is more than twice that of oats. Because of this, it must be fed with caution and in relatively small quantities. It is best fed in conjunction with other grains to balance its starch and nutrient content.
This high energy content is the basis behind corn's not-so-accurate reputation as a 'heating feed that makes horses hot and hard to handle'. This assumption probably originated with owners unknowingly or carelessly substituting corn for an equal quantity of oats in their horses' diets, thus supplying more than twice the energy. Feeding by weight, rather than by volume, is crucial when feeding corn.
Contrary to popular belief, corn is not a 'heating' feed. The greatest amount of internal heat in the horse's body is generated through the digestion (or more specifically the microbial fermentation) of fiber, not starches. Therefore, increasing the amount of hay in your horse's diet is actually creating more heat. Feeding more hay in winter will generate more body heat than feeding more corn. Corn is a good winter feed for horses in that it provides lots of energy per pound, and energy needs increase during cold weather.
The corn kernel is not truly a seed; it is a fruit containing a seed. This seed, or embryo, is known as the germ and is normally located on the flat side of the kernel facing the tip of the ear. The kernel itself is composed of a thin outer coating or bran termed the hull, the germ, and the starch. The germ houses most of the oil in the kernel and also contains protein. The starch, composed of both a soft flour-like starch and a hard starch that is bound with protein- and carotene-rich gluten, comprises the greater part (about 60%) of the kernel. The list of nutrients in a kernel includes the minerals calcium, phosphorus, chlorine, sulfur, sodium, magnesium, iron, copper, manganese, and trace minerals; vitamins A, C, Bs (riboflavin, thiamine, niacin, and inositol), E, and essential fatty acids; and water.
Moisture content in corn raises a red flag among horse people. Moisture allows for the possible growth of molds and toxic substances produced by fungi and mold, such as aflatoxins (aflatoxicosis) and fusarium moniliform (moldy corn disease); both are potentially fatal if ingested. Horses are much less tolerant of feed with any degree of fungus or mold than other animals; any musty or moldy feed should not be fed. Also, horses may colic, develop liver damage or suffer from botulism after eating moldy feed.
Moldy corn poisoning (equine leukoencephalomalacia) can cause horses to go off feed, become depressed, lose coordination, and often die. This fungus lives in the soil and is often found on moldy corn stalks or corn that has been stored wet. Moldy corn poisoning outbreaks are most common with horses grazing corn stalks, however horses fed commercial feeds have also been affected.
Molds and fungi thrive in moist conditions. Grain can become infested with them as a result of wet weather conditions during the growing season or exposure to moisture during harvest, or if stored in damp, humid, or hot conditions. Of all the grains fed to horses, corn is the most likely to be contaminated by molds.
Horse owners can use their basic senses of sight and smell to detect moldy feeds. Grains generally develop a somewhat sour or musty odor and are usually gray and discolored. Unfortunately, however, the more fatal molds cannot be seen; thus, often the most deadly corn looks perfectly safe.
Feeds mixed with molasses make molding difficult to detect until the feed is obviously sour; the fragrance and color of the molasses may mask the problem. If using mixed feeds, feed top quality mixed feeds; generally those manufacturers have strict regulations on the amount of moisture in the corn they use for their feeds. The moisture content in corn should be less than 15%; some companies require it to be as low as 11%. Once the feed is processed and combined, however, that moisture level may change. Also, most manufacturers use preservatives that may or may not be healthy.
The processing of corn by cracking, flaking, steaming, and rolling, which is often thought to make corn more digestible, is in fact detrimental in that it exposes it to the elements, namely moisture. Whole corn is a bit more challenging to chew than cracked or flaked corn, but chewing is a natural, needed activity. Whole corn, properly chewed and mixed with saliva, can be just as easily digested, if not more easily, than processed corn. Without processing, corn will also maintain its nutrients longer and can more easily resist the effects of moisture. Unless your horse has special needs, whole corn makes more sense for the horse. Maintain a good dental program to enable your horse to chew properly.
When feeding corn, purchase the best quality whole corn available and make sure its moisture content is less than 15% to reduce the risk of spoilage and mold. Store it properly, as with all feeds. Use it as part of a complete feeding program. Only mold-free corn should be fed; it is far less costly than caring for a sick animal, or losing one. Careful and observant feeding will minimize the risk of causing permanent damage to horses.
Avoiding the problem
Controlling the moisture content of feed is the most important factor in preventing mold and spoilage in storage. As storage temperature and humidity increase, so do spoilage problems. Good grain storage facilities greatly reduce the risk. The storage facility should have good ventilation with low humidity, protection from direct sunlight and moisture, and a cool, consistent temperature.
Keep all grains in a dry, tightly covered container to keep out moisture and insects and to protect nutrients.
When in doubt, throw it out (or better yet, return it to dealer)
Feed by weight rather than volume.
Feed grains in smaller portions, in two or more feedings.
Purchase only the best you can buy. Supplementing with vitamins and minerals will not get rid of mold, does not always make up for lack of grain nutrients, and is more costly.
Buy small quantities more often to ensure freshness.
Use as part of a total nutrition program.
Keep out of reach of horses!
Given the proper assistance, owners can formulate their own grain mixes. Depending on the locality, the availability of straight grains, the number of horses to be fed grain, and the storage facilities, this may be a sensible option. For information on preparing your own feed, consult your veterinarian, equine feed specialist, or county and state agricultural extension offices.
While hay and forage make up the primary diet for horses, whole grains are a natural, palatable staple for many horses' grain formulas. Whole grains, when properly combined, can be an important supplement to the equine diet.