For horse owners who don’t have their own hay fields, the process of planting, cutting, drying, and baling hay can be a bit of a mystery. It can go wrong in a number of ways.

If the hay is harvested at the wrong time, loss of nutrients and mold becomes more likely. Toxic plants and pests can also end up in the hay, increasing the chance of a sick horse on your hands.

Given how sensitive horses are, it is wise to obtain hay from a responsible and reliable seller. Additionally, you need to check every bale you give to your horse. Quick quality check at feeding time can save you big headache in the future.

Mold is one of the most common hay hazards, but fortunately, you can protect your horse from both mold spores and toxins (mycotoxins) that some types of mold produce.

Why is moldy straw dangerous?

Moldy hay often causes respiratory problems in horses. Recurrent airway obstruction, known as heaves, is a lung disease that compromises a horse’s ability to breathe. It is similar to asthma in humans and is a chronic condition that can only be controlled and not cured.

Possible signs of elevation include:

• Coughing
• rhinorrhea
• Increased respiratory rate
• breathing difficulties
• The presence of a “bump line” caused by the enlargement of the abdominal muscles to aid breathing

Mycotoxins can also cause digestive issues such as colic, diarrhea, and weight loss. A weakened immune system and a lack of nutrient absorption make the horse more susceptible to a host of health problems. Organ damage can occur, including kidney and liver failure. Depending on the severity of the reaction, toxins can lead to death. Reproductive problems are another consequence of eating moldy hay. Mares may undergo unexpected miscarriages, stillbirth, or produce a foal with birth defects.

How does straw become moldy?

Mold develops when moisture does not evaporate in an appropriate amount of time. Sometimes this happens around the time of harvest, in which case your best defense is a knowledgeable hay farmer.

Cutting and drying hay is delicate work. If the hay is cut too early, the moisture content will be too high and lead to a risk of mold growth, but if it is cut too late, some desirable nutrients will be lost. Luck plays a role, too. All hay farmers can tell stories of how an unexpected rainstorm flooded their crop after it was cut and it was meant to dry out in the field.

Hay can also grow mold due to improper storage. Hay should be stored in dry conditions, preferably off the ground. If it is impossible to store hay in a barn or storage shed, keeping it under a tarp or other protective material will help, but this is not ideal. You will also need to put pallets or a waterproof barrier between the hay and the ground, or moisture will seep in and negatively affect the bales at the bottom of the mound.

Proper ventilation reduces the moisture content of thatch and is especially valuable in areas with high humidity. Even hay that is carefully produced and stored can end up with some mold indoors, so checking the hay before feeding is still always a must.

How to protect your horse from rotting hay

To better protect your horse from rotting hay, inspect it before feeding it. Even if most bales are healthy, mold can be found in only one or two flakes.

Before giving your horse any hay, take a minute to check the following:

• Smell. Is there a scent you don’t know? The smell of mold may be an obvious red flag, but any unusual smell should catch your eye.
• the color. If the straw changes color, set it aside. Discoloration can indicate heat or moisture damage, or problems during the curing/baling process.
• soil. All the hay is a little dusty, but the excessive dust indicates that the hay may have been wet and dried out by now.
• Monotheism. Make sure the hay is free of foreign plants, insects, and other foreign objects.

If you have to travel and are concerned about conditions in transit or at your destination, consider using a bale bag. Be sure to choose a bag with built-in ventilation, such as Derby’s Originals Extra Large Straw Cover. Straw bags are useful for maintaining freshness as well as reducing waste to a minimum.

Instead of throwing your horse’s hay all day on the ground, you can put it in a net or feeder. Any hay feeder for horses should be installed at a height that allows the horses to eat with their heads down. Placing it too high increases the chance of inhaling dust and mold spores.

If you are concerned about the quality of your local hay sources, cubes or pressed bales can be good solutions. Options like Standlee Grab & Go’s premium pressed alfalfa bale are popular because they are shrink-wrapped after being chopped, dried and packeted at the optimum time.

If you have already purchased hay for horses and think there may be a problem with mold, you can also test the hay. Some of the tests can be completed in your barn while others take a little longer, but either way, the results will give you peace of mind.