Well, there are probably a combination of problems that are causing these issues. I would check your exposure meter and make sure it is shooting in what we call a matrix mode that takes into effect all the areas in the viewfinder when calculating exposure. Some only look to the center of the photo or a spot in the middle. Put the camera on the full exposure matrix mode. Also check to see that your camera isn't set for exposure compensation and overexposing by a stop...
Second, this is a difficult backlighting situation. The camera is obviously exposing for the dark portion on the side of the sheep that is in the shadows. Consequently it is blowing out the highlights. Some cameras can handle these tough situations while others can't. If the camera shoots in raw mode you can bring back the blown out highlights with your raw editor. If it only shoots jpg then you are pretty well stuck with what the camera shoots. In this instance, you could have looked on your camera screen and saw that the camera was overexposing the shot. You then could have compensated by underexposing the shot by about 1 stop.
I hope some of that makes sense...
Shawn