aspiring photographer-please voice your opinions

[DomBee8]

I am an aspiring horse photographer. I really want to be a theriogenologist (a equine reproductive specialist) but I would like to use photography to help me through high school and collage and use it as a hobby after that.These are some of the pictures I have taken of my horses. They would be better if the backgrounds weren't so bad. Please tell me what you think. I have compared these to pictures I have taken in the past and I think I am doing better.

http://i5.photobucket.com/albums/y160/DomBee8/Website%20Pics/Halo%20On%20A%20Star/10115a0c.jpg
http://i5.photobucket.com/albums/y160/DomBee8/Website%20Pics/APs%20Mojo/582f02a0.jpg
http://i5.photobucket.com/albums/y160/DomBee8/Website%20Pics/Diamond%20Rio/8533d5bc.jpg