I don't have a horse, nor do I board, however, I thought I
would share what I use for feed storage. They are made by rubbermaid. They are
pricey but they stay closed and they keep feed fresh, and they last a life
time. They are 30 gallon gray round trash cans. The lids lock to keep out
rodents. They are very heavy duty. Lowes and Home Depot sells them. They
also sell the tray with the wheels for underneath them. I think I paid around
$32 for each. They are much heavier then normal trash cans..
How much feed are you wanted to store? I can put about 120 lbs in one of
these. 3 bags of Ultium fills it. You can bungie one to the inside of your
trailer very easily by weaving through the handles. Good luck!