They look good, the next step is to start adding some detail. You have the basic shapes right, but if you start giving it more of the "sketching" look and start with shading and such like the person above said, you could really make some good improvements!
The legs look good, I think you need to maybe make the hooves a little bigger? Or look at the shape more carefully. Much better than I can draw though. (I only draw stick people and stick horses) haha
Off to a good start. The horses look generally proportional, so that's a plus...Love the expression on the head shot. Even for a basic drawing, you managed to catpure the horse's personality well. As with what everyone said above, start experimenting with shading look for the darker aspects of the photo and try to play with shading and altering the firmness of your pencil strokes.
As for hooves, you picked a very challenging angle to draw hooves from. I'd practice drawing from photographs of the side of the horse, not angled towards the camera. You may also want to find pictures of just the horse's legs and draw them at a larger scale for practice to get the shapes down.
Hope this helps. Can't wait to see more of your work.