Hay either consists of grass or legums (alfalfa, clover), or a mix. Generally, legumes are higher in protein, carbohydrates, calcium and vitamin A compared to grass hay.

When evaluating hay for purchase open a bale or two, shake out a flake and examine it for maturity, uniformity, and condition (color and odor).

MATURITY. Hay that is cut early (in late-bud to early bloom) when the plant has a high ratio of leaves to stems is preferable. Leaves contain the highest amount of protein, and thus provide greater feed value. Hay cut later in its growth stage has larger woody stems, fewer leaves and a lower feed value.

UNIFORMITY. All hay has some variation to it. That said, look for gross variations in the type of grasses present and the presence of weeds and undesirable plant matter (burs, needle grasses, rough bearded grasses with sharp awns) or other objectionable materials (insect carcasses such as blister beetles, wire, nails, other debris). Likewise, hay should be comparatively dust free. Put your own face into the hay and breathe in. Do you notice dusts or a moldy odor?

CONDITION. Properly cut and cured hay should have a bright green color. Sun-bleached bales are light yellow or gold on the outside. Often these bales are still palatable as this condition is only found on the outside of a few bales that were exposed to the sun during storage. Hay that is yellow throughout may have been cut at a more mature stage and contains comparatively more stems or lay on the field before baling.

Hay that is dark brown or black has often been exposed to the weather, heat or stored at too high of a moisture content. This hay often has a musty odor and may contain clumps that are caked together. Hay in this condition is usually not suitable for feeding to horses.

Keep in mind that hay quality can vary widely. If you purchase hay from a new source it is best to integrate it into your horses' diet slowly, mixing it with their familiar hay.

Some horses experience mild intestinal upset with any change and it self-resolves, other horses may experience more severe abdominal pain (colic), when a new hay is introduced, especially if the change is drastic. When feeding new hay, pay particular attention to your horse's general attitude and appetite.

Talk to your supplier about the origin and quality of their hay openly and frankly. Many suppliers will take back rejected bales and give you a credit towards your next purchase.

Do not skimp on hay. Do not buy poor quality hay - "cow hay" - for your horses. Try to establish a long term relationship with a supplier you trust so that you can reduce the number of times you must transition your horses to a new hay. On the other hand, if you buy very high quality hay you probably will need to feed less of it and less grain, or you may inadvertently cause unwanted weight gain. When in doubt, talk to your vet about the type of hay you feed and your concerns about purchasing hay from a new or different supplier.

Regarding sampling of hay for forage laboratory analysis, see the particular lab's guidelines. A good online resource is equi-analytical.com.