Horse Texture Glitch

If you go in front of a horse, an then go straight toward it, you can see inside the texture and see its mouth, even if its actually closed. If you pull a horse in a corner and then go straight toward it, the horse couldnt escape and you can watch it full inside.

What I expected to happen was...:
The horse goes bach, or I couldn´t go any much more forward

What actually happened was...:
I looked into its mouth (texture)

Steps to Reproduce:
1. Fetch a horse
2. Place yourself in front
3. go straight toward the horse
4. You can see the inside of the head and the mouth, untill the horse escapes.