What is Alfalfa?
Forage for horses can be divided into two categories—grasses and legumes. Grasses you’re likely familiar with include orchard grass, timothy, and bermuda grass and are long and stemmy. Forage legumes, such as clover and alfalfa, are members of the pea family and, so, are cousins of peanuts and garbanzo beans.
It was one of the first domesticated forages, planted and harvested in what is now Iraq, Iran, and Afghanistan several thousand years ago. When alfalfa was first brought to the eastern part of the U.S. in the 1700s from Europe, it didn’t survive well—partly because of wetter soils and lower pH. However, when settlers brought alfalfa west in the 1800s during the California Gold Rush to grow livestock feed, it did quite well.
The biggest benefit of alfalfa for horses is that it tends to be more nutrient-dense than most grasses when harvested at the same stage of maturity,” says Martinson. It typically contains more digestible energy, more crude protein and calcium, and fewer nonstructural carbohydrates (sugars and starches).
How Does Alfalfa Help with Gastric Ulcers?
It's commonly thought that horses turned out on pastures are better off than those that are confined. However, if grass hay is the only hay they are fed, horses can still get gastric ulcers.
The prevailing belief on why alfalfa helps prevent and reduce gastric ulcer incidence in horses is because of its buffering capacity. Buffering capacity is the ability of a substance to neutralize the pH of a system. In our case, that would mean that the ability of alfalfa to neutralize the acidic pH of the stomach is greater than most commonly used horse feeds. The buffering capacity of alfalfa may be credited to its high magnesium and calcium content, which will often come with acid-neutralizing bicarbonates, along with the high protein of the alfalfa itself. While the proteins are made up of amino acids, these acids are considered "weak acids," and would actually help further neutralize the "strong acid" solution found in the stomach. Given that protein content seems to be the best predictor of buffering capacity across several different feeds, it is possible that these amino acids are more effective in neutralizing stomach acid than bicarbonates.
A 2007 research study conducted at Texas A&M University, found that alfalfa hay reduced the severity of ulcers in young, exercising horses.
Ulcers can reduce a horse’s appetite and feed intake and cause weight loss, poor hair coat, colic, and reduced performance. Many factors can contribute to ulcers, including stall confinement, intensive exercise, feeding infrequent large meals, and stomach outflow obstruction.
In this study, 24 Quarter Horse yearlings were kept in small dry lots and fed two different diets for 28 days each, with a 21-day pasture washout period between. The first diet included coastal Bermuda grass hay and a 15% pelleted concentrate, while the other diet included the same amount of alfalfa hay and the same concentrate. All horses were exercised three times per week using a horse exerciser.
Ulcer scores were significantly lower for the alfalfa diet than for the Bermuda hay diet, and the 11 horses in the alfalfa group with ulcers at the beginning of the study all improved their ulcer score by at least two grades. However, one horse went the other direction, developing ulcers while on the alfalfa diet. Only five of the 12 horses starting the Bermuda diet with ulcers had ulcer score improvement, and only two of those improved by the two grades or more. Ulcers tended to be worse at the end of the Bermuda diet period.
Another notable finding was that while ulcer scores didn’t change significantly from the end of the Bermuda diet to the end of the pastured washout period, they increased significantly from the end of the alfalfa diet to the end of the washout period.
So only one of 23 horses fed alfalfa worsened vs. 16 of 24 on coastal Bermuda. Eleven of 12 horses on alfalfa remained ulcer-free compared to only three of 12 on Bermuda.
Does Alfalfa Form Affect These Benefits?
Researchers from the University of Leipzig, in Germany, set out to investigate the effects of feeding two forms of alfalfa with different particle sizes versus a grass hay on weanlings’ gastric mucosa.
Prior to weaning, the team, led by Ingrid Vervuert, PhD, DVM, an assistant professor of veterinary medicine, introduced 39 male and 31 female Warmblood foals to a diet consisting of about 6 pounds of alfalfa chaff, 6 pounds alfalfa pellets, or free-choice grass hay. The team provided all the foals with a special mix of oats, soybean meal, and/or a mineral supplement to ensure each treatment group had a similar nutrient intake. The team performed gastroscopies on the foals prior to weaning and after 16 days on their treatment diet to determine gastric ulcer prevalence and where the ulcers occurred within the stomach.
Conversely, a recent New Zealand research claims that gastric ulcers can be healed by feeding a commercially available fermented alfalfa chaff. The study used 12 horses diagnosed with ulcers. During the study, all the horses were fed approximately 33 lb of modified bio-fermentation Alfalfa chaff per day for six weeks. There was no control group reported. By 14 days, 67% of the horses had no ulcers, and by 28 days all the horse in the study had no ulceration. These are amazing results, but this study is difficult to assess because no detail on how the horses were managed and fed pre-study was provided. If horses had limited or no access to forage before starting the trial, then it would be expected that stomach health would be improved upon introduction of fiber, regardless of the type. There is also no detail on how the horses were housed before or during the study. Based on published research and practical experience, had these ulcerated horses been turned out to pasture or fed alfalfa hay, the ulceration would have improved in a similar fashion. It will be interesting to see further study on the difference between various fiber forms (Alfalfa Hay, Chaff, Pellets or Cubes) using this experimental method.
Which Horses Benefit from Alfalfa?
The biggest benefit of alfalfa for horses is that it tends to be more nutrient-dense than most grasses when harvested at the same stage of maturity. It typically contains more digestible energy, more crude protein and calcium, and fewer nonstructural carbohydrates (sugars and starches).
Because it’s so nutrient-dense, it is a good feed for underweight horses.
It can also be beneficial to horses with muscle problems that are prone to tying-up (due to their increased protein needs) or horses with equine metabolic syndrome (EMS) due to the lower amount of nonstructural carbohydrates.
Alfalfa is ideal for horses on high planes of nutrition, such as lactating broodmares, growing horses, thin horses, racehorses, performance horses, or young foals that aren’t getting enough milk.
With growing horses, however, use caution in amount fed, simply so they don’t grow too quickly or get too big too fast and become at risk for DOD (developmental orthopedic disease).
We know that for horses sensitive to sugar or carbohydrates (e.g., horses with insulin resistance, pituitary pars intermedia dysfunction, etc.), building a diet on a good foundation of forage is especially important—the oats, corn, and barley that make up many feeds are 55-75% carbohydrate.
Some grass hays are also too high in sugar for these horses, and this is where a legume diet or mixed legume/grass diet can help lower total sugar intake.
Choosing the right hay for proper balance can be challenging, however.
For instance, a horse that’s overweight and insulin resistant needs a lower-sugar hay (alfalfa) but not the additional calories. Often what is suggested is to do a mix where those horses receive some alfalfa added with a low-sugar grass hay.
You can add alfalfa pellets or cubes to a grass hay diet for the same effect.
Alfalfa is also suitable for horses prone to gastric ulcers, because the extra calcium acts as a buffer against stomach acid. You might offer performance horses alfalfa an hour or two before work or competition, during which acid can splash up into the non-glandular part of the stomach (where the cells of the lining do not produce protective mucus). The simple act of chewing creates more saliva, which also helps buffer stomach acid.
Owners might also offer alfalfa to horses needing to develop more muscle, particularly along the topline. This is because alfalfa provides amino acids needed for muscle regeneration.
Which Horses Should Not Eat Alfalfa?
Some owners believe alfalfa makes horses “hot,” but there’s no scientific basis for this. Alfalfa does have more energy compared to grass hay of similar maturity, so perhaps a horse eating a lot of alfalfa in the absence of exercise may have more energy. The biggest issue with alfalfa is weight gain in horses that don’t have adequate exercise.
Additionally, it supplies more nutrients than most non-working horses need, leading to obesity and its associated issues. So feed overweight horses or easy keepers just as you would the sugar- or carb-sensitive ones—offer them a mature grass hay with lower caloric content over a rich legume like alfalfa.
Alfalfa is a good source of nutrients for sport horses, but owners might want to avoid offering it when horses are working hard in hot weather. Protein metabolism creates more heat than fat or carbohydrate metabolism. This added heat can impair the horse’s ability to dissipate heat. They might even suffer from dehydration (due to extra sweating and increased urination from the alfalfa breakdown/flushing from the kidneys) and be more likely to experience heat stress. Extra protein cannot be stored in the body like extra fat or carbohydrates and must be excreted.
A horse eating more protein than the body can use will also drink more water (to help flush out the additional waste products). This creates more urine and, thus, more ammonia odor.
Ammonia in stalls can irritate airways and make horses susceptible to respiratory problems. This is especially true with foals, since they are smaller and spend more time lying down. Ammonia is heavier than air and thus is concentrated near ground level.
While feeding extra protein is wasteful, a high-protein diet in itself does not hurt a healthy horse. It can be detrimental, however, to horses with impaired kidneys or liver. These individuals have problems processing and excreting protein and should be kept on a very low-protein diet.
It also isn't recommend feeding straight alfalfa to endurance horses due to its protein and calcium content. The last thing you want on an endurance ride where the horse is sweating for long periods is the increased body heat, water needs, and urine production described. High levels of calcium, on the other hand, can interfere with the horse’s ability to mobilize bones’ calcium stores during exercise. Endurance athletes can benefit from small amounts of alfalfa, just like any other performance horse, but make sure it’s not their sole forage source.
Many performance horses are not worked to the point of dehydration, so they can handle a higher percentage of alfalfa. In California there are many cutting, reining, and other performance horses that eat a lot of alfalfa hay (due to its wide availability) and balancer pellets, and that’s their entire diet and they do fine.
Other horses that do best with limited alfalfa are horses with the genetic muscle disease hyperkalemic periodic paralysis (HYPP). These horses are affected by hyperkalemia, or an excessive amount of potassium in the blood, which causes their muscles to contract more readily than normal and makes them susceptible to sporadic episodes of muscle tremors or paralysis. These horses are particularly sensitive to alfalfa’s high potassium content.
Potassium levels in forage are dependent on what the plants are pulling out of the soil, however. It can make a difference how and where the alfalfa was grown and whether it was fertilized with manure—which really drives the potassium levels higher. If you have a sensitive horse, it is always best to get your hay tested to be sure of what you are feeding your horse.
Some horses with un-pigmented skin should probably not eat alfalfa because they could be prone to photosensitization caused by black blotch disease. This is a mold that causes black blotches on the undersides of the leaves of legumes, including alfalfa. Horses ingesting this mold may experience excessive sunburn—which seriously affects they un-pigmented areas of their body. The more serious issue with these horses, however, is the liver damage from the toxins in the mold.
This article is inspired and comprised of information gathered from the following sources: