Should I hang water in the trailer or offer it at stops? Should I unload the horses for at anytime during the journey (say at the half-way mark), or leave the horses on the trailer the entire time?

Thanks in advance for all your help and advice!!

Don't unload anyone until you get there. Hang hay bags, they act as a pacifier, keeps them ocupied, bring extra hay for refills. We don't offer grain, just oat hay. Offer water at fuel/bathroom stops. AND KEEP ROLLING!!! No sit down dinners until the horses are stalled at their new residence.

400 miles is not too far.... Maybe 8 hours or less. We haul 600-800 miles on a regular basis and have never had any trouble

Since you will most likely be hauling in heat a good idea is to get them hydrated a few days before you leave. Many of the distance riders I know will add a little salt or some electrolyes to the feed a few days out to be sure the horses have been drinking plenty. Hay will actually help the gut to hold some moisture and keep working. If the horse is very comfortable in the trailer, they will finish it but often they will just eat a little at a time and sometimes not at all. Offer them water at each stop. Take water from home as they will be more likely to drink it. I don't like to haul over 8 hours myself but that's just because I don't like to sit in the truck much over 8-10 hours..LOL. You can feed a wet meal of beet pulp before you go if your horses are used to it. It's great to get them hydrated and it's good bulk to keep them pooping. Not necessarily a huge meal but something nice and wet. I think it's dangerous to unload the horses en-route for the most part and what happens if they decide they don't want to get back in!? Many recommend to stop about every 3 hours to give the horses a break. This works for me somewhat as I usually have to use the bathroom by that time anyhow. We make quick stops, especially if it's hot. The first time we hauled 7 hours we actually stayed overnight after 3 hours. Seems kind of silly now.

Have a nice trip =)

I'd suggest longer days (much longer if you can find a tag team driver) making it a shorter overall trip. 

We bought a Holsteiner mare and foal in New Mexico and had them shipped to PA. The shippers had an impressive rig, sport truck with sleeper; an open floor plan, fully insulated, air ride trailer with camera hooks ups, A/C and heat. The two horses were not tethered, and allowed to move about in an area equivalent to a smaller stall.

The drivers' only stops were for some meals, fuel, and a specific hands on look at the horses on a five to six hour basis. The horses had a constant supply of water and hay; straw bedding was up to their knees. They were stiff and sore after their long straight through trip, and with a couple days' rest, quickly settled into their new environment.

Those drivers said this was easier on the horses than multiple days of traveling with long breaks. That is, assuming they are healthy and not in distress. Spending more time in recovery before any activity is most beneficial.

Gard

I agree with headhunter about making longer days and an overall shorter trip if possible. 

With Gard's post, however, you need to take into consideration the difference in the rig. A large rig with a nice ride and open stalls isn't exactly equivalent to a smaller stock trailer in the ride the horses receive.  Overall, I would imagine the horses would have less problem with a straight through trip in one of the big rigs where they can move around. We had one shipped here from Texas and we paid for a box stall for him since he was young and hadn't been hauled. He obviously seemed pretty comfortable as he ate a whole bunch of hay according to the hauler. He still eats a whole bunch of hay  =)

Have a safe trip. One of the places I would like to go to ride is Alaska. I'm jealous...

Have you ever tried shredded paper for bedding? It has many advantages over sawdust and shavings; high rate of absorption and no dust, and many places can't give it away. It works great afterward in the garden and completely breaks down. Just a thought.

Have a safe trip and enjoyable stay. It sounds like quite an adventure. Take lots of bug spray.

Gard

AQHA 123, I always tie my horses too but I tie them long enough so that they can lower their heads enough to clear their sinuses. I wouldn't have a problem with not tying them but they always manage to get into some sort of mischief if I don't. We hauled all 4 on one trip and they were back there just rocking around. Not enough to worry me, but I could feel them. When we stopped at the ag station I found that one had come untied and had managed to turn enough to irritate his neighbor. Tied him back up and the moving around ceased. I'm not sure how he came untied as it was a trailer tie with a panic snap on it. Go figure.

Wood pellets are great...

http://www.shavings-direct.com/wood_pellet_bedding.php