The price of hay in the United States has increased dramatically during the last several years due to increasing fuel costs and lack of supply.  Consequently, this increases the overall costs of keeping your horse and if there is anything that can be done management wise to save money, it would be worthwhile.  Some producers prefer to feed hay to horses on the ground and others prefer to feed in feeders.  To study different methods of feeding hay, a study was performed at Sam Houston State in Huntsville to determine the least wasteful method of feeding hay to stalled horses.  In this study, twelve 2-year-old quarter horses were fed coastal Bermuda hay for 2 weeks both in feeders and then on the ground.  The study determined that horses fed hay on the ground wasted over 7% of the hay while horses who ate from the feeders wasted only a little over 1% of the hay.  Using feeders also helped to reduce fecal and urine contamination and trampling. 

Although there were no nutritional deficiencies noted as horses gained the same amount of weight regardless of feeding method, the difference in wasted hay was certainly significant.  No signs of colic were observed feeding in stalls or on the ground.  So it seems that feeding hay in feeders is the best method to prevent waste.  I am assuming from reading this study that the stalls were concrete with mats although this was not mentioned.  Consequently, if horses were fed on the ground in stalls with sand or dirt, it is likely they would lose even more hay.  Regardless, if you feed your horses hay, using feeders will save hay and money in the long run.