Equine Nutrition

Angelica Veitch
Susan C. Eades, DVM, PhD, DACVIM

Do you know what is the best feeding program for your horse? What about supplements? Here are some guidelines to help you avoid feed-related illnesses in your horse and to feed him to maximize his performance and well-being.

There are no strict rules to feeding horses, but one principle is good to follow: keep it simple. The horse's digestive system is designed to live on one of the world's simplest diets: grass forages. The horse evolved on grass plains, roaming wide and far at will, and grazing for 18 to 20 hours a day. Today's domesticated horse doesn't usually live this lifestyle, but is stabled and asked to be a companion and an athlete. By keeping in mind the natural diet of horses and the new demands placed upon them, you can achieve a balanced diet that will keep your horse happy and healthy.

Adapted to long hours of eating small amounts of fibrous forages, the horse has a surprisingly small stomach for the size of the animal. The stomach only holds 2-4 gallons, and does little of the actual digestion. Horses can neither vomit nor burp. Food passes from the stomach into the small intestine in about 30 minutes. The small intestine holds 10-12 gallons, and is approximately 70 feet long. From there feed travels to the cecum, a large, 7-9 gallon, blind-ended compartment, where fermentation of the ingesta begins. From the cecum it passes to the largest part of the digestive system, the large colon, holding about 20-25 gallons. Here fermentation continues, and microbes (bacteria and protozoa) do the bulk of the digestive work. These microbes convert fibrous feeds into nutrients your horse can use, and are essential to his health. The microbes can be killed by some kinds of antibiotics or rapid changes in diet, leading to colic and other digestive problems, so always consult your veterinarian before making changes in your horse's diet or giving medication. Feeding a diet with a high grain content leads to fewer of these "good" microbes, and promotes growth of microbes that cause intestinal disease. From the large colon digesta goes to the small colon where water is absorbed and fecal balls are formed. From there it goes into the stall for you to clean up. This entire process takes 36 to 72 hours.

The important parts of your horse's diet are fat, protein, energy (carbohydrates), vitamins and minerals, fiber, and of course, plenty of fresh water. Depending on your horse's level of activity, and stage of life, the amount of these nutrients necessary may vary. In general, the requirements are: fat 8-12%, protein 8-14%, carbohydrate 30%, and fiber 50%. Horses should also drink 6 to 8 gallons of water per day for a 1000 pound horse. For idle horses or pleasure horses under light work, all of these requirements can be met by good quality pasture and hay. Horses under moderate to had work, young growing horses, and brood mares in the last trimester or lactating may need supplementation with grain or pellets. Here are some good rules of thumb for feeding horses:

• Horses should consume 1.5 to 3.0% of their body weight per day. At least 50%, probably more, of caloric requirements (80% of feed by weight of feed) of this should come from forages (grass and hay).
• Ample turn-out and grazing time is important and will help keep your horse from getting bored, and his digestive system working as nature intended, however, if pasture is limited or unavailable, you can minimize the effects by feeding several small meals per day. Stabled horses should never be fed only one meal, but two works well for most horses. Three meals a day is better for horses under strenuous work such as endurance riding and three-day eventing.
• Don't ride your horse right after he finishes eating. Give him at least an hour after a big meal. Also don't feed him right after riding. Give him at least half an hour, longer if he is still hot. It is okay to ride a horse that has been eating hay or out on pasture.
• Observe your horse's eating habits. Does he always finish everything? Does he take a long time chewing? This way you can notice problems early. Here are some signs of problems to watch out for--a normally good eater eating slowly, or picking at his food can be an early sign of colic. A horse that dribbles grain or drops balls of chewed hay (called "quidding") can be a sign of dental problems. A horse that coughs and looks anxious after eating may be choked. A horse on lush green pasture standing with front feet outstretched and looking uncomfortable may be foundering. Good quality pasture should be of a forage grass such as ryegrass or bermuda grass, and relatively free of weeds. You can keep weed growth down by periodically mowing.
• Good hay should be green, not yellow or brown, and it should smell sweet and fresh, not musty or moldy. Different kinds of hay include the legumes, such as alfalfa and clover, and the grass hays, such as bermuda grass or timothy. In general the legumes are higher in vitamins and protein, and are more expensive than the grass hays. Horses should eat at least 1 pound of hay per 100 pounds of body weight (1% of body weight) for good digestive health. Intake will vary with quality of hay, so a horse eating poor hay will not eat enough of it to fulfill his requirements.
• Feed hay before grain to take the edge of your horse's appetite, so that he won't bolt his feed. Feed bolting can lead to choke and gas colic. Greedy eaters can also be slowed down by placing large stones (not pebbles) in the feed bucket.
• Making your own grain mixtures is unnecessary. There are excellent premixes available that have been balanced for all the important nutrients. Making your own grain mixes or supplementing balanced diets may take the "balance" out of the ration. You also may consider feeding a pelleted diet. Although not as tempting as sweetfeed, pellets are convenient and digestible, and picky eaters can't sort out their favorite parts. Be careful though: there are very few pelletted feeds that are high enough in fiber to be complete feeds. Some horses become chronically colicky or get diarrhea when on a purely pelletted ration with no hay.
• Most commercially formulated grain mixtures and pelleted feeds are well balanced for nutrients, vitamins and minerals, so supplementing is unnecessary, but always feed a high-quality, well-known brand. You get what you pay for. Vitamin supplements may be necessary if your horse has decreased feed intake due to illness or old age.
• Even high quality feedstuffs do not supply the necessary amount of salt in your horse's diet. Horses need at least 0.25% of their diet in salt and most feeds only provide 0.1%. Supplement this by giving your horse a free choice salt block. High heat and exercise will increase his need for salt, too.
• For horses expected to be athletes, old horses, or horses that have been ill, you may want to add fat to the diet. Fat is a good way to add extra energy without extra bulk, and can be done by top dressing feed with 1/4 to 1/2 cup of corn oil per meal.
• Keep grain feeding to a minimum. Horses that do not work much do not need grain at all if fed good quality forages. Ponies need very little grain even if they are working, as they have a tendency to obesity and founder. Even working horses should only be fed enough grain to keep them sleek and energetic. 1 to 2 quarts per meal should be enough for most moderate working horses. Brood mares and high performance horses may need more, ideally divided into 3 or more meals a day. If your horse loses condition or energy, you may need to increase his feed, but consult your veterinarian to rule out other health problems. Weight loss can be a sign of systemic illness or parasites.
• Good quality forages, hay and commercially formulated grain mixtures or pellets are balanced in vitamins and minerals, so these do not need to be supplemented unless horses are on high grain diets or poor pasture, despite what the supplement ads tell you. Moderate amounts of healthy treats such as apples and carrots are a good source of vitamins, too.
• There are a few things you might consider supplementing: biotin supplements can help promote healthy hoof growth in horses with slow growth or cracks. Glucosamine and chondroitin can help horses with early signs of arthritis.
• You may have heard about the importance of selenium in horses' diets. Louisiana soils have sufficient selenium to keep your horse healthy. Even in areas deficient in selenium, such as the Northwest or Northeast, be careful! Never supplement selenium without consulting your veterinarian, because it can be toxic.
• Another thing you may have heard of is the importance of calcium and phosphorus. The ratio of these two minerals to each other is important as well as the amount. In general, horses consuming mixed pasture and hay, or pasture, hay and grain have diets balanced for calcium and phosphorus. Horses should be given hay when not out on pasture if they have less than 12 hours a day of pasture access. Hay is higher in calcium than phosphorus, and grain is higher in phosphorus than calcium. Horses on high grain diets may need calcium supplementation. Alfalfa is a good source of calcium.
• If your horses spend a lot of time outdoors in hot humid weather, or are asked to exert themselves heavily, especially in hot weather, consider adding an electrolyte mixture to meals to replace minerals lost in sweat.
• Fiber is an extremely important, often overlooked part of the diet. Besides being essential for holding water in the digestive tract and aiding digestion, fibrous feed such as hay that require chewing keep your horse from becoming bored and chewing wood or acquiring other vices. The added salivation from chewing also aids digestion.
• Speaking of chewing--have you had your horse's teeth checked lately? Uneven wear can cause sharp points that interfere with chewing, causing weight loss due to insufficient intake or poor digestion. Old horses may also have cracked or loose teeth. Get your veterinarian to check your horse's teeth at least once a year. Horses younger than five or older than twenty may need teeth checked more frequently.
• Horses need access to fresh clean water at all times. Lack of water can cause dehydration or impactions. Water consumption can be a problem when horses are stressed or traveling to shows. They may be reluctant to drink strange water that tastes different or is in a different bucket. Adding a few teaspoons of kool-aid to the water at home for a few weeks before shows and then adding it to the water at shows may help disguise the taste of unfamiliar water if you have a horse that is picky about drinking.

It is impossible to cover every aspect of equine nutrition here, but these are some of the important points to get you started. Your veterinarian can help you design a feeding program that is right for your horses, and provide important information about dietary-related illnesses such as obesity, founder, ulcers, colic, and orthopedic disease. There are also good books available on equine nutrition--ask your veterinarian to recommend one.


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