Questions regarding my dogs health condition.

Question
QUESTION: My dog is a Doberman aged 4.He weighs 31.8kg. He is having some skin problem and is feeling itchy most of the time. thus, he is also finding it difficult to support himself using his back legs and this causes me to know whether he is lacking calcium or is it just as a matter that he is already old. I have been feeding him lamb(adult breed food), home cooked chicken or eggs with rice. basically I feed him at least twice daily. is it possible for you to explain on the proper diet he needs and also about his skin problem. thanks a lot.

ANSWER: It is possible the other things besides the dog food are leading to an unbalanced diet.  I would cut everything out but the dog food. Brush hiom daily with a soft bristled brush, and seldom if ever bathe him.

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QUESTION: what about his difficulty of having to support himself????

Answer
Joint problems are too common.  It could be genetic or poor feeding as a puppy.  You could have a vet examine him, but you may not be able to do much except give him pain killers.  You can give him common aspriin, buffered is best.  Give 11 mg per kg of body mass every 12 hours.  A regular 325 mg tablet would be close enough.  Don't give him any of the newer pain killers unless prescribed by a vet.    

Being overweight adds to any joint problems and may even be part of the skin problems.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx