It's nice to treat your horse to special foods sometimes. However, there are a few things they probably shouldn't eat. What shouldn't you feed your horse? Here is a list of the foods that probably shouldn't be included in your horse's diet.
Fruit in Large Quantities
Many of us like to feed our horses apples for treats. But sometimes fruits can become too much of a good thing. A belly full of apples or any other fruit can easily cause colic and may lead to founder. You probably may not feed your horse more than one or two pieces of fruit. The danger is when horses have access to windfall fruit from a wild tree, or someone dumps a basket of spoiled apple over the fence thinking they’re giving the horse a ‘treat.’
Lawn and Garden Clippings
Lawn and garden clippings can contain several hazards. Clippings can contain toxic plants and there are several common garden plants, like lily of the valley and rhubarb leaves, that fall into this category. Some weeds are toxic. What gets sprayed on lawns and gardens to control pests and weeds may be toxic too, even if it was sprayed a long time ago. Just-cut or semi-wilted plant material can be a problem in itself, even if it appears to contain nothing but grass. Because horses don’t have to graze and chew the material for themselves, they may bolt the food and fill up on it much faster. This can lead to choke and colic. The sugars in freshly cut or slightly wilted clippings can cause an imbalance in the horse’s gut, leading to laminitis. Put lawn and garden waste into your composter or manure pile, not over the fence into your horse’s pasture.
Deadly Equines, The Shocking True Story of Meat-Eating & Murderous Horses by CuChullaine O'Reilly, the Founder of the Long Riders' Guild explores the fact that horses can and do eat meat (and can appear to behave in quite a violent manner to get it). However, that they can and do eat meat does not mean that they should. A horse may be trained to eat meat, or it may be driven to it by need. This doesn’t mean that a regular diet of meat in the long-term is a good thing. Your horse may like an occasional bite of your hamburger or tuna sandwich and can eat it without harm. However, since we don’t know the long-term effects on most horses, a diet high in meat would be inadvisable (along with expensive). Horses have the teeth and digestive system of a highly specialized herbivore. Few of us are going to take our horses on Antarctic expeditions and our horses will likely be healthiest eating the diet their digestive system evolved to digest.
You may already know someone who gets uncomfortable after they eat cabbage, broccoli, kale, Brussels sprouts or other vegetables in the cabbage family. Your horse may feel the same type of discomfort after eating ‘gassy’ vegetables like these. A few leaves or sprouts may not matter, but dumping the old plants over the fence probably isn’t a great idea.
Moldy or Dusty Hay
If good pasture is not available, good-quality hay is the next-best choice. However, never feed your horse dusty or moldy hay. To do so could damage its lungs. Here’s why it’s not okay to feed hay that’s only a bit dusty or has a bit of mold in it.
Many people may be surprised to learn that bran mashes are not recommended. Horses eat a lot of fiber in their normal diet, so adding bran can actually affect the gut flora. Bran has little nutrition, so there are much better things to feed a horse than bran or bran mashes.
Eating alsike clover may cause a very nasty sunburn, sores in the mouth and cause problems like colic and diarrhea and ‘big liver syndrome’. Alsike clover is common in pastures. It can grow up to 30 inches high (76 cm) and in addition to its clover-shaped leaves has a round flower head of pretty pink. You can tell it apart from red clover because it doesn’t have the distinctive white ‘V’ on the leaves that other clovers do. If your horse snaps up a few stalks of alsike clover occasionally, it’s probably okay, but prolonged consumption or a large amount at once may cause problems.
Cattle feed contains supplements that are good for cattle but are very toxic to horses. Drugs like rumencin are routinely added to cattle feed. These drugs can be deadly for horses. This is why it's a good idea to buy feed from mills that specialize exclusively in making horse feeds.
Silage and Haylage
Feeding haylage (sometimes called baleage) and silage to horses is more common in the UK and Europe than it is in North America. Feeding silage and haylage to horses can be tricky. There are some definite benefits to feeding these fodders, like higher nutritional value and low dust. But the manner in which the hay is cut and baled can lead to the risk of botulism poisoning. Horses are very sensitive to botulism and being infected can lead to paralysis and death. Because the hay is baled at a high moisture content and is wrapped in plastic it is the ideal environment for botulism to grow. Soil carrying botulism, poultry manure, small animals and birds can be baled into the hay, contributing to the growth of the bacteria.
The Ontario Ministry of Agriculture, Food and Rural Affairs recommends against feeding haylage and silage to horses. A vaccine is available, but it only protects against one of the five types of botulism. Care has to be taken that uneaten silage or haylage is cleaned up. There is a possibility that frozen silage can lead to colic, and we don’t yet understand if there are long-term effects of feeding acidic (and treated or conditioned hay) fodders to horses.