Horse Illustrated Magazine

Q: Can you feed a purebred Arabian straight alfalfa? I have an 8-year-old Arabian mare who is underweight. The vet said to put her on alfalfa and grain, but the owner of my boarding stable says that straight alfalfa is bad for Arabians and they need to eat only straight grass hay or a grass/alfalfa mix. Is there any truth to that, and if so, why?

A: The most important aspect of your question is this key fact about forages: not all alfalfa is created equal. Yes, as a generality, alfalfa is higher in protein, calories, and calcium than grass hay, since alfalfa is a legume. However, between one farm’s alfalfa and another farm’s, exact percentages of these nutrients can vary drastically due to farming and harvesting techniques, growth of the plant, and what stage of growth the hay is when cut. There are in fact instances where a poor quality late season cut of alfalfa may contain less protein and calories than a leafy, lush early cut of grass hay. To truly know the exact percentages of protein and other nutrients in a particular cut of hay, you would need to submit a sample of the forage for analysis. Many agricultural extension agents associated with local universities can provide such a service at a relatively low cost.

Alfalfa has a somewhat bad reputation among horse owners, but it is often misunderstood and utilized improperly. Due to its inherent composition of high caloric content and high protein, this type of forage will cause weight gain if fed to idle or lightly worked adult horses, and it can result in growth issues and developmental orthopedic disease if fed inappropriately to young stock. It has also been implicated in the development of enteroliths (intestinal stones).

However, if a particular horse is in a metabolic state that requires relatively high levels of calories and protein, then alfalfa has a place in this animal’s diet. Examples of this type of situation would include mares in the third trimester of pregnancy, heavily lactating mares, young growing animals, heavily working horses, and those that are undernourished, sick, or otherwise in a metabolic state of catabolism (when the body is breaking down its own muscle stores for energy).

As such, it is true that most adult horses do not need straight alfalfa and most maintain an appropriate body weight on grass hay only. However, in the case of underweight animals such as your mare, adding protein-rich alfalfa can be helpful in putting on weight in some cases. I disagree with the rule that straight alfalfa is bad for Arabians, as each horse’s dietary needs, regardless of breed, are entirely dependent on that individual’s metabolism, overall health, and daily activity. Instead, in most cases, it is more accurate to say that straight alfalfa is unnecessary for healthy adult horses with a sedentary or light work lifestyle.

However, while alfalfa can be used to put weight on a thin horse, this must be carefully controlled. It is important that undernourished animals gain weight slowly and dietary changes be made gradually to prevent counter-productive health problems such as diarrhea, impaction colic, and even laminitis. While it is not clear if your mare is underweight due to environmental or metabolic reasons, I recommend you work closely with your vet to monitor your mare’s weight during this period of methodical weight gain, taking care to set clear goals as to when to gradually wean her from straight alfalfa, as she will likely not require such a robust diet as she achieves an adequate level of body condition.