Written by: Shannon Pratt-Phillips, PhD.

Equine nutritionist, Shannon Pratt-Phillips, PhD, explains that not all hay is created equal and offers hints on purchasing and feeding this diet staple.

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Hay is the staple of many horses’ diets, particularly when pasture is not available due to season or housing limitations. Hay is made from plants such as grasses or legumes that have been cut and dried, and depending on what type of plant the hay is derived from and its maturity at cutting, the nutritional quality is greatly affected.

Hay can provide substantial energy (calories), as well as other nutrients such as protein, vitamins and minerals. Hay is also very high in dietary fibre, which is extremely important for the health of your horse’s digestive tract. Furthermore, the consumption of hay, because it takes a while for your horse to chew and eat it, helps him satisfy his natural foraging behavior. For these reasons, hay (or other forage sources such as pasture if available) should be considered the most important part of your horse’s diet (after water, of course!). So, let’s learn a little more about your choices.

Making Hay

Grass hay is hay derived from grasses such as timothy, orchardgrass, fescue or brome. Timothy and orchardgrass are probably the most commonly fed grass hays for horses, as they are palatable and tend to have good nutritional profiles for most classes of horse. Alfalfa is the most common legume found in hay, but clover and birdsfoot trefoil may also be used in hay-making. Mixed hay has a split of grass and legume (and perhaps even more than one type of each), which often optimizes the nutritional profile of the hay for many horse classes.

Legume plants have the ability to ‘fix’ or use nitrogen from the atmosphere and incorporate it into protein (and can do so better than grasses can). Hays derived from legumes, therefore, tend to have higher levels of protein than grass hays. Legume hays are also slightly higher in energy and calcium than grass hays.

As the plants grow, their nutrient composition changes, with nutrients such as protein being higher in younger plants, while fibre increases in older plants (thereby decreasing calorie density). Thus, a less mature plant (‘early bloom’ or ‘vegetative’) at cutting will tend to have a higher nutrient density than a more mature plant (‘late bloom,’ ‘full bloom,’ or ‘mature’).

Hay Analysis

While some general nutritional information can be inferred based on the plant type, cut and maturity level of the plant, it can be very difficult for the average horse owner to accurately classify their hay.

In fact, there is much variation even once plant type and maturity is known. The only way to truly know the nutritional profile of your hay, therefore, is to have it tested. Many agricultural laboratories will analyze hay, quite economically (often for less than $35 depending on what information you want).

In general, information about digestible energy, protein, fibre content, calcium and phosphorus should be sufficient for most horse owners, though information about starch and sugar content may be beneficial. It is also fairly common to test the selenium levels (selenium, along with vitamin E, is required for proper development of muscle tissue), as selenium content of soil is highly variable, and, therefore, influences the selenium content of the hay grown on it. Depending on the growing and cutting conditions, you may also consider having your hay tested for moulds and toxins.

What and How Much to Feed

In general, most horses do not need very high protein in their diets. In fact, most are overfed protein. Anywhere from seven to 12 per cent protein content in the hay should be sufficient for most horses. The bigger concern when it comes to hay quality is with respect to things like weeds, foreign objects (like wires, insects or dead animals!), mould, etc. Hay should be green, leafy, free of mould, dust weeds and foreign objects, and should smell good. A lower protein hay that is green and leafy is far better for most horses than a higher protein hay that is mouldy.

Square (rectangular) bales can be very convenient for feeding horses kept in stalls, and bales can be relatively small.

Round bales are another option for horses, particularly if they are kept outside and pasture is limited. In general, a round bale should be consumed within a few days to prevent mould development and wastage in the elements, and are, therefore, only suitable if you have enough horses to go through a round bale within that time (typically four horses is sufficient). If you have more than six horses in a field, you may need to place more than one round bale out at a time, to avoid competition among horses. Round bale feeders may also be useful to minimize exposure to the elements and wastage.

Hay may also be purchased as hay cubes, which have been cut and cubed (typically one inch cubes). These may be a good option for horses that are sensitive to dust or older horses with poor teeth, as cubes are easily soaked.

Health Concerns

There are relatively few health concerns that you should be aware of when choosing hay for horses. As mentioned, moulds and toxins may be present in hay, particularly if it was rained on during cutting or drying. Again, tests are available to identify if these are present in your hay. Dust can also be of concern, particularly if you have a horse with heaves. Soaking or steaming hay can not only reduce dust particles, but may also kill some moulds. Soaking hay can also reduce the sugar content of the hay, which may be beneficial if you have a horse with insulin resistance, or is sensitive to sugars for other reasons (soak hay in the water, and then discard the water). If feeding round bales, there is also a small concern for botulism, and, therefore, a vaccine may be recommended by your veterinarian. Fescue hay is often infected with a mycotoxin that can negatively impact broodmares, so it should not be fed to pregnant or lactating mares. Alfalfa hay may also be infected with blister beetles, which are highly toxic to horses.

Hay selection and feeding should not be taken lightly, as it is a vital component of the horse’s diet. Work closely with your hay dealer and an equine nutritionist, to help select the hay that is best for you and your horses.


The “cut” of the plant refers to what point in the growing season the hay was harvested; first cut would be the first cutting of the year, second cut is the second cutting, etc. Depending on what plants are growing and their growing season (timothy, for example, is a cooler season plant, which will grow more early in the season and then become dormant mid-summer when the second cutting may occur), the timing of the cutting may affect the maturity and dominance of plant species present (if it is a mixed plant field).


Hay storage is an important aspect of purchasing hay. Typically, the more you purchased at a time, the cheaper it is. Unless you have adequate facilities, however, you may consider purchasing smaller loads. Over time, hay will dry out and there can be significant losses to not only the nutrients within the hay (particularly vitamins), but also to the total amount of hay itself. Keeping hay out of the elements and off the ground is the best way to minimize losses.