I don't know the facts on your question. I do know that my hay guy stores my hay for me and brings me 40 bales at a time, and sometimes by the time I use all I've bought for the year out of storage it's about 8 months old. It has always still smelled fresh and my horses have always eaten it well.
Because of the hay shortage in my area, my horses are getting Fall 2007 cut timothy/alfalfa at their night time feeding with their pm grain, and November 2006 cut Orchard Grass/Fescue/Clover free choice during the day in their pasture. They are 50lb square bales, not the big rounds though. They get about 2 bales a day of the old hay in their pasture between the 4 of them. They were stored properly and still smell good and are mold/dust free. It's not my ideal hay feeding but I didn't have much of a choice this year. My horses seem to be doing fine with it, and it's over a year old. They have been on this schedule since November and haven't lost any weight or had any problems on the old hay. I guess maybe it depends on where it's being stored and the type hay you're dealing with. Each is probably different. I'd say the main concern with old hay is making sure it clean, dry, and free of mold.
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Last edited by horseloverinVA; 02-15-2008 at 10:52 AM.