The early signs of danger when feeding the uncured hay can be noticed in bloating of the gut between the hip and the ribs, as well as in the redness of the eyes.
The high quality, well stored and cured meadow hay from forage harvested from non-swampy soil is a foundation of correct nutrition for all farm animals, especially during their growth, because it contains all (complete) nutrients needed for their development and maintenance. If we feed hay in the first weeks of harvesting, we cannot take full advantage of this high quality forage, because when not properly cured it could not only seriously endanger the health of the animal and his use, but sometimes also his life.
In some cases we need to feed new and uncured hay before the four or six weeks after harvesting, when the biological process is unfinished, because we have nothing else to feed, or the supply of the old hay will not last till the new hay is ready to feed. In such case is recommended to mix the new hay with the old or with some good quality cured straw. The bales should be opened and aired out for at least 24 hours.
Feeding the fresh not “sweated out” (uncured) hay can cause serious colic , sometimes resulting in twisted intestines. The early signs of this danger can be noticed in bloating of the animal, in progressed stage redness in the eyes and later with high fever and irregular heartbeat. Horses often die in extreme pain. Therefore, in principle we feed the new hay after it is finished, that is adequately ripe, sweated out and ready to feed. For the above reasons we do not feed hay to horses and other young farm animals until after 5 or 6 weeks after it was put away in the hay barns. The sweating of the hay, or the curing process very much depends on the storage facilities as well as on the weather. If the storage facilities are not well vented out, or if the humid or rainy weather persist for a longer time, the curing process takes even longer, or the hay will often spoil, hence six weeks may not be enough in some cases nor it will guarantee a good quality of the hay.
If we do not know the curing process or the time when the hay was harvested when we buy it, we are taking chances with the health of the animal. Many people involved in the provision of the hay to the stables tend to misinform the unsuspecting clients. It is therefore recommended not to feed the new hay after purchase for the same length of the time (5 to 6 weeks). In other words, do not trust anyone and make sure that you have always enough old hay to take you well past the new harvest. If and when you buy new and uncured hay, make sure that you are storing it in a well-ventilated barn and well above the moisture from the ground.
In some cases the farmers or dealers add chemicals to the hay, to prevent it from spoiling, which is another issue. Preferably avoid such hay, since this can also contribute to colic in some more sensitive horses. This danger usually shows in tighter (dryer) than normal feces when such hay is fed. Next time you get really “beautiful GREEN” hay, especially alfalfa, it does not mean it is good for the horse, just because it looks good to you. One needs to have some experience in the hay department in order to evaluate good quality horse hay.