Story by Eleanor Kellon, VMD
It isn't a "perfect" food, but alfalfa can be a good staple in the horse's diet. There are a few caveats, but the key here is balance.
For equine seniors, pelleted alfalfa may be easier to chew and provide more nutritional value than an equivalent amount of grass hay. Few things create more arguments and opinions when it comes to feeding horses than whether alfalfa should be a part of the equine diet. Some say there's nothing better. Others view it as a kind of poison. The truth, of course, lies somewhere in between.
Let's look at the pros and cons of alfalfa, and explore some of the myths.
Some Advantages Horses love it! No argument there. Give a horse the opportunity to choose among flakes of all-grass hay, grass-alfalfa mix, and all-alfalfa, chances are he will chow down the alfalfa flake first. Alfalfa is tasty to horses.
Alfalfa has lower indigestible fiber than grass hays. High quality ("dairy") alfalfa supplies 20% to 25% more calories per pound than grass hays, although the difference is much smaller for more mature cuts of alfalfa. Heavily pregnant or lactating mares, and young rapidly growing horses, benefit from alfalfa's high protein content. Alfalfa is also a rich source of calcium. Cubed and pelleted alfalfa tends to be very high quality. It is harvested before it becomes too mature so that the cubes and pellets hold together well. The major quality issue to be concerned with is overheating during processing, which will damage the protein. Pellets and cubes should be green, not brown or black on the outside.
Alfalfa Myths vs. Facts
Myth: The high protein in alfalfa causes osteochondritis dissecans (OCD), a joint disease of young horses.
Fact: High protein does not cause OCD. Rather, low protein is a risk factor for OCD. What's true, though, is that the very unbalanced mineral profile in alfalfa could contribute to OCD.
Myth: The high calcium in alfalfa can prevent OCD and other bone problems in developing horses.
Fact: Calcium is important to developing bone, but so is phosphorus, magnesium, protein, and the trace minerals. Adequate mineral levels, in correct proportions, is the key.
Myth: Alfalfa's high protein causes kidney problems.
Fact: High protein is not harmful to the kidneys. However, extra protein is metabolized to ammonia, which must be excreted by the kidneys. To handle this extra demand, the horse will drink more water and make more urine.
Myth: Alfalfa's high protein makes a horse "hot."
Fact: For reasons that really aren't clear, some horses are more energetic when being fed alfalfa--but it isn't the protein.
Myth: Alfalfa causes heaves or allergies.
Fact: Alfalfa is no more likely to cause an allergic reaction than any other type of hay. Molds growing in the bales can cause respiratory tract symptoms, but the same molds can--and do--grow in any type of hay.
Myth: Alfalfa cannot be fed to HYPP horses because of the high potassium.
Fact: Grass hays can be high in potassium too. In fact, depending on when they were cut, they could be even higher. The Downside Insulin-resistant horses prone to laminitis may be sensitive to alfalfa. The cause isn't entirely clear, but it may be related to alfalfa having more sugar in the form of glucose, and higher starch.
The high calcium content of alfalfa causes an imbalanced calcium/phosphorus ratio if not corrected by other feeds or supplements. Most adult horses seem to tolerate this, but it's not ideal for pregnant mares and growing horses. The high calcium also causes hormonal shifts that make it difficult for the horse to rapidly mobilize calcium from bone stores in times of need. This can cause "thumps" or muscular problems in horses working hard, or weakness and muscular problems in mares when they first start to produce milk.
Due to alfalfa's high protein content, excess protein will be burned as a fuel and the waste is eliminated in the urine as urea, which is converted to ammonia. Horses will drink more, leading to wetter and smellier stalls.
Alfalfa can be trickier to cure and bale than grass hays. It needs a low enough moisture level so that it doesn't mold, without being put up so dry that all its leaves shatter and fall off. Grazing on an alfalfa pasture requires the same precautions as feeding alfalfa hay, plus some additional considerations. For example, digestive upsets may be an even bigger problem, especially in the spring and fall when wide temperature swings can lead to rapid changes in the composition of the plant. And unlimited access to such a highly palatable food as alfalfa may lead to significant weight gain. Having an alfalfa-grass mixed pasture may not help much because there's a good chance that the horses will seek out and eat the alfalfa first, exclusively.
Alfalfa is prone to have more "fines" (broken, crumbled leaves that fall out when you open the bale). Since this is where the bulk of the nutrition is, this can be a considerable loss. Try putting your alfalfa bale on an empty feed bag before you open the bale, and feed the small pieces that fall out in the feed trough or bucket. For the horse who might have some respiratory sensitivities, fines can be mixed into a meal or wet down slightly, but, in general, the particles are much too large to actually be inhaled into the lungs.
High-alfalfa/low-grain diets have been linked to the formation of enteroliths ("stones") in the intestinal tract, which can cause colic and may need to be surgically removed. Not the Perfect Food, but …
In summary, while alfalfa isn't a complete, "whole" food for horses, it doesn't have to be avoided either-if you make it a point to balance your horse's diet so he's getting everything he needs in the right amounts. There are many horses who need extra calcium or protein in their diets, and alfalfa is an excellent natural source of those nutrients. Because of its taste appeal, higher digestibility, and the fact it is easier to chew, it is often a valuable addition to the diet of sick horses or senior horses. There are many areas of the country where alfalfa is more readily available than grass hays and very reasonably priced. If you use alfalfa as your sole hay type, just be sure to get advice from a nutrition professional on how to properly balance your feeding program.