08/27/2025
Have you ever been told that alfalfa makes horses "hot"?
Well, when we take a closer look at this statement, the truth is much more nuanced, and it depends on several factors.
First, it's important to discuss which definition of "hot" you are referring to. The horse's core body temperature? Or, "hot" as in the horse's behavior?
Taking a look at the nutrient content of alfalfa hay vs. grass hay, alfalfa hay has higher digestible energy; meaning it will have more energy per pound, but less fiber. In addition, it also has lower hydrolysable carbohydrates than grass hay, thus lessening its effects on insulin levels.
Alfalfa hay is also higher in protein. This is where an increase in core body temperature comes into play, because protein increases metabolic heat generation when used for energy compared to fats and carbohydrates.
However, protein conversion to energy is less efficient, therefore horses typically aren't utilizing protein in large amounts as their energy source. Excess protein will be excreted through the urine instead of being stored in the body.
In terms of making a horse "hot" in behavior, as mentioned earlier, alfalfa does have more energy per pound than grass hays. So, if alfalfa is introduced to a horse's diet WITHOUT properly balancing for energy (calories), there is a potential for increased reactivity.
In addition, feeding alfalfa alters the gut microbiome compared to grass hay. Alterations in the gut microbiome can be linked to changes in behavior. Therefore, owners may observe behavioral changes that are reactions to the change in the gut microbiome and not the alfalfa itself.
All this considered, IF the diet is balanced properly for energy and protein, there is no evidence that supports that there will be alterations in terms of horses becoming super reactive and "hot" behaviorally when they are on alfalfa hay. However, it can slightly increase their core body temperature due to its high protein content.
If you have questions regarding your horse's diet and feeding alfalfa, contact your veterinarian.
Thank you to the Horse Owner Education Committee for providing this information.