A horse can get a hoof and leg throught the 4 ". I had one horse that did this and it looked like someone skinned his leg, He was kicking. I cleaned it , pulled the skin down , put some salve on it and betadine, wrapped the heck out of it. He healed. Only had to cut one small peice of dead skin off. Another horse got her shoes caught, and the goats would push out the bottom and crawl under it. Pygmy goats tend to jump more in my experience with them, and my Nubian does would go under. The sheep stay in the 4" . I have hot wire around the top of the fence, I did have 3 strands of hot wire up, but it was always shorting .