Here is the second page from my sketchbook. Here you can left any critics you want. Dear Maz Bourne and Bogusred, you are very skilled artists and I would be glad if you find the time to look at my drawings and leave a feedback, what you think of my skills.
The first thing I noticed when looking at your horse sketches is that it sort of looks like you are trying to put human anatomy on a horse. Especially with the horse on the lower left of this piece. It looks more like a human shoulder than a horse's shoulder. I think what you need to do is get some reference and learn the anatomy of a horse. Whenever any artist attempts to draw an animal they are unfamiliar with should get anatomical reference. Especially for a horse because horses are probably the hardest animal to draw.
I've uploaded a sample for you to show the basic rhythm of a horse. The one on the left is just a profile showing the rhythms of the bone structure. The one on the bottom right is a redrawing of yours. and the top right is my redrawing of your pose with the knowledge of anatomy.
I just uploaded it for a sample. Don't use my work as reference as I don't have a lot of experience drawing horses. The description of it mentions a couple good anatomy books that you may want to check out.