Just my opinion, but I think I would have like to have seen a side angle view to this horse and carriage. We could see more of his harness get-up and part of the carriage that he is hitched to. From what I can see, he may be fairly thin and a side view would be disturbing if that were true, but would definately hit home the slave part. I do like the fact that we only see the feet of the owner. Technically, I find nothing wrong...it is well focused and lighting is appropriate.
I agree with your title completely. I have been marking "animals in captivity" down a couple of marks, but since you have acknowledged the fact, you aren't losing the points!! I like the head-on angle you have used here. Could be interesting if you were a little lower and looking up at the horse as well.
wow.. the composition on this shot is gorgeous... the color and exposure are very strong as well... the red really sets things off... great work :) - setzler