Fermentation of fiber in the horse’s hind gut is the major heat source that keeps horses comfortable through colder months. Therefore, a steady hay supply is crucial. While many horses continue to graze some pasture, hay usually provides the majority of winter forage. Type and amount of hay varies depending on a horse’s size, metabolism, and workload. At a minimum, start with the basic guideline of feeding enough hay to equal about 1.5-2% of the horse’s body weight (around 15-20 pounds a day for a horse weighing 1,000 pounds) and increase as needed when the temperature drops.
Easy keepers and horses doing minimal work do well on medium-quality grass hay (can contain a few weeds, might have been cut when a little more mature than optimum).
Horses with average metabolisms will do better on good-quality grass hay (mostly free of weeds, made from grass that was not over mature at cutting).
Heavily exercised horses or those with special needs (older horses, thin horses, horses recovering from illness) might need a grass-legume mix or even a straight alfalfa hay.
As a general rule, horses that shiver and regularly clean up every scrap of hay probably need to have their hay rations increased. Horses that simply enjoy eating might also consume every flake in sight, but their rations do not need to be increased. Use a weight tape every few weeks through the winter to track body condition changes, which will reveal if a heavy-coated horse that appears fat is actually losing weight. Likewise, horses that leave some hay untouched might seem to have been overfed, but it is also possible they are leaving weeds, rough plants, or moldy flakes. Inspect the rejected material and purchase better-quality hay if necessary.
Stalled horses have plenty of time to pick through their hay, munching a few mouthfuls now and then as the hours pass. Pastured horses that eat hay in a group setting need to be monitored to be sure that low-status animals have adequate access to hay. Very timid horses might need to be fed hay separately or in smaller groups. Space hay piles widely in the field and offer several extra piles to minimize this problem.
Mike D. Maxson