last years hay?

Does hay lose it's nutrition over a year? It was properly stored, no mold or anything. A coworker has offered it to me for the right price. One of my horses had been eating this exact hay until a month or so ago with no issues. I guess the biggest concern is how does the nutrition hold up through another winter.......... It is alfalfa.

GREAT question!! Yes, hay loses nutrition over the course of about a year after curing, but it loses no more nutrition after that. I am very jealous that you have 1 year old alfalfa hay. Alfalfa is SO RICH (and hard on a horse's kidneys) that I PREFER year old alfalfa to this year's, but when you've had a bad year for baling hay, it's very hard to find it in the Spring of the year. After one year your alfalfa hay will be lower in protein but better for your horse. Feed it and enjoy!

It's more than enough to feed my horses(20 tons for 3 horses) for the entire winter so I will start hauling it this weekend. He cuts his own hay so he just wants me to haul it off to make room for the new hay...........

This is not exactly how it works! Oxidation, water, radiation, etc. degrade hay. The more exposed to the elements hay is the faster it degrades. The more "stored under ideal conditions" it is, the slower it degrades. Hay in the center of a stack in ideal conditions will be great for many years. The top 1" of a stack will go downhill quickly. If you can find some common sense, it is very easy to understand.

Could you define "stored under ideal conditions"? Just asking because I have 40 bales reserve stored on pallets in my garage for my two horses. It is grass hay, not alfalfa. The garage is ventilated.