How does everyone store their horse's feed in the trailer when going on long trips? I'm talking like a 3 week-long trip. We haul 5 head and typically mix up baggies of grain with their supplements before we head to races (2-5 days in length) but this will obviously be a much longer trip and it's a lot of food to take not to mention takes up space. At home we store the baggies in totes but that will take up most of the room in the tack area. We have a 5 horse trailer so we can't use the stud stall as storage. 

You only have so much room, so there is no mystery solution unless you had a hay pod added to the roof of yourt trailer. On the times I'm gone for a long time I call ahead to feedstores at the locations where I will be. Things like grain etc are the same across the country BUT hay like alfalfa, you have to be careful where its grown. TX, OK, etc have blister beetles. This is where cubes come in handy. 

I haven't been on that long of a trip, but I have put bags of feed under the back seat. You can do baggies of supplements and put them in a 5 gallon bucket or a box or something. I store things in the LQ shower sometimes, not ideal but it works. When I'm stopped I cna just toss it out the door into the horse part. And usually put a sheet or whatever I have on hand in the bottom of the shower to catch debris if I store stuff in there. I've done the same with hay bales on thr LQ floor, just put them on a sheet. And throw them outside under the trailer when stopped & using the LQ. I've packed shavings bags up in the bed many times. None of these ideas are super ideal but got the job done for me. I haul alone now and usually just 1 horse so I haven't had to get creative in a few years. But many times of hauling 3 horses with friends, even just 4 day weekends, we'd throw all the feed/bedding etc in the LQ and just unload it when we got there. 

I drop bags of feed in the storage space under my mangers.  I dish supplements up in condiment cups for every day use, so I just grab the number required into a bag or bucket and throw them in the trailer.

I'm trying to get everything off the floor. Water buckets above on shelves.

Blankets and coolers can go in these.

Home Depot

Very smart thinking here!!!!! How are the baskets mounted? Can you take them down when you need to put things away? I really like this ideal of extra storage. The wire basket looks to be a fixed storage but the baskets look like they can be taken down and put back up when needed.

Do you know what brand these black bins are? 

(Google) Gladiator Garage Works 24" wide mesh basket.. 

Get one of those large hay storage bags and you can put 2-4 bags of grain in there and just put it in the back of your truck. That way if it rains, the bags will stay dry. The other way I have done it is to carry unopened bags of grain in my living quarters and just put them in the trailer after all the horses are unloaded. By the time the trip is over you are down to a manageable amount.