Why is my Labrador scratching?

Question
I have a 20mth old Lab male and he has been constantly scratching around his tail and groin area.I have found no signs of fleas but he has been bleeding at times.He is on a strict chicken necks,dry biscuits and vegetable diet.We live on a large block and near bush but he mainly stays on the back deck in the cool.What could be causing this?

Answer
It could be a number of things.  It could be a simple matter of the anal glands.  have a vet or groomer empty them.  

It could be a dietary problem.  Homemade and raw diets are very difficult to get right.  See http://www.avma.org/onlnews/javma/jan05/050115ww.asp  He could also have serious problems whose symptoms you may not see until too late.  I would put him on almost any of the commercial diets.  If you would feel better about it go with one of the premium ones such as Eagle Pack Holistic or California Natural.  If the problem still doesn't go away, back to the vet.