It is next to impossible to find a rigid, straight line in the outline of any animal. Nature seldom uses a straight line. And so hen drawing animals, neither should you.
Here are some tips for drawing realistic animals:
The Horse - The body and legs of the horse fit into a square, with the head and neck extending out of one corner. The legs start downward from the midpoint of the square. Divide the main square again into four equal smaller squares. The length of the head will be about three fourths of one these smaller squares. Get these proportions right and you’re halfway done.