Looks good, we also use the water off the barn roof to fill our water troughs. I would be careful using pressure treated wood around horses. If they crib it can kill them.
PT wood hasn't killed my horses. They chew on it sometimes. A 1,300 pound animal would have to ingest plenty of PT wood to feel any effect. Most agriculrual fences have PT posts too. I have plenty of splinters from those posts. /forums/images/graemlins/smile.gif
I really like the gutter and downspout with the drain. I don't have any livestock yet, but I will keep that in mind. I may try it out for my dog. I was going to build him a new kennel with a roof. That would work out great.