Myth: "You should never give a horse straight alfalfa."

Never say never. In California and the southwest United States, horses are routinely fed straight alfalfa as the only forage. In that region, alfalfa is cheap, plentiful, and the horses do quite well. While some horses may not need alfalfa, others would truly benefit from receiving alfalfa. The difference lies in what nutrients alfalfa provides, and what the horse actually needs. Alfalfa contains more energy, protein and calcium than most grass hays, such as timothy, brome grass, orchard grass, etc (Table 2). This nutrient profile makes it most suitable for young, growing horses and lactating mares, because they have high protein and mineral requirements (Table 3). By comparison, alfalfa exceeds the protein requirements of idle horses and performance horses (Table 3). That does not mean these horses cannot receive straight alfalfa. It just means alfalfa provides more protein than these classes of horses need. Alfalfa also tastes good, so it's useful when you've got a finicky eater or a horse with a poor appetite. While alfalfa is more nutrient-rich than most other forages, it is not any richer than many other feeds commonly used for horses. For example, good quality pasture is often higher in calories and protein than alfalfa hay (Table 2). Leafy, rapidly growing spring pasture grass may contain 20 to 26% protein. By comparison, mid-maturity alfalfa hay will contain 16 to 18% protein.

Foals do not have the same capacity as an adult horse to house and digest lots of mature forage in an effort to obtain the nutrition they need for growth. Foals have greater nutrient needs than adult horses, but a digestive system only one-third as big. As a result, growing horses need a nutrient-dense diet-lots of nutrition in a small package. Alfalfa can help us meet their high energy, protein and calcium needs without having to add alot of extra bulk to the diet (Table 3). High protein does not cause developmental orthopaedic disease (more on that later), nor does high calcium. Furthermore, we can adjust the high calcium to phosphorus ratio in alfalfa with a suitable mineral supplement.

Very few people who circulate this myth have ever actually experienced these problems themselves. And since most people don't want to risk their horse developing colic or laminitis, this rumour stuck. I'm not saying it couldn't happen (never say never). Some horses may be predisposed to colic and founder, particularly obese horses and fat ponies. For these easy keepers, alfalfa may be too much of a good thing and is probably better avoided. However, most feed-related cases of colic or laminitis tend to result from feeding grain, alfalfa or other feeds incorrectly. Because it is richer in energy and protein, alfalfa should be limit-fed—fed in a fixed amount—rather than offered free-choice. Horses that are fed too much alfalfa or allowed to eat as much as they want often relish the forage so much they will become obese. And obesity is certainly a predisposing factor for colic and laminitis. Because alfalfa has a higher nutrient value, less alfalfa hay will be needed to meet the horse's requirements, compared to the amount of grass hay needed. For example, a mature, 1100-lb horse used for light work will only need 16 lbs of alfalfa each day, but would need 22 lbs of timothy hay to meet dietary requirements. Risk of colic or laminitis also increases when people switch from a mature grass hay to a good alfalfa hay without giving the horse time to adjust to the diet change. The microorganisms in the horse's digestive tract need time to adjust to new feeds, particularly when going from a low quality feed to a higher quality feed. So, if you are switching to a straight alfalfa hay, adjust the horse to alfalfa gradually over a period of 1 to 2 weeks (each day or two, replace more of the old hay with the alfalfa). And remember you will be feeding a fixed amount of alfalfa, probably less hay than you were feeding before. The same is true for grazing a horse on an alfalfa pasture. Horses can safely graze on an alfalfa stand if given time to adjust to the forage. Start with 2 to 4 hours of grazing and gradually build up the turnout time over 1 to 2 weeks. Keep in mind that mature horses may not need to graze 24 hours per day to obtain all the nutrients they need if the pasture is of high quality. To make better use of your pasture and to avoid obesity, consider restricting grazing time.

Although alfalfa may provide more protein than mature horses need, there is no evidence to suggest that a moderate dietary excess of protein is detrimental to healthy horses. Protein is made up of amino acids, which are composed of carbon, hydrogen, oxygen and nitrogen. When horses (or humans) consume more protein than they need, the carbon, hydrogen and oxygen from the amino acids are used for energy and the excess nitrogen is excreted in the urine. Horses consuming alfalfa (and other high protein feeds) have been noted to drink more often and urinate more than horses consuming lower protein diets. But there is no reason to believe that a horse's kidneys will be damaged when this occurs. It's only when a horse already has pre-existing kidney disease that the high calcium and protein in alfalfa can aggravate kidney dysfunction. When feeding alfalfa, it is important to provide free-choice access to water to ensure the horse can flush the excess nitrogen from its body. When alfalfa-fed horses receive only restricted access or limited amounts of water, they often produce more concentrated brown, thick urine.

Suggested Reading

Canola Council. Truths and myths about canola. http://www.canola-council.org/thetruth.htm

Evans, J.W., A. Borton, H. Hintz and L.D. VanVleck (1990) The Horse. W.H. Freeman Co., New York

Geor, R.J. (July 2001) Chilling Out After Exercise. The Horse. pp 89-94

Harris, D.M. and A.V. Rodiek. (1993) Dry matter digestibility of diets containing beet pulp fed to horses. In: Proc. 13th Equine Nutrition and Physiology Symposium. pp 100-101.

Lewis, L.D. (1995) Equine Clinical Nutrition. Williams & Wilkins, Baltimore.

Lewis, L.D. (1996) Feeding and Care of the Horse (2nd edition). Williams & Wilkins, Baltimore.