I have had success with anemic patients using home made diets and semi-cooked organic food sources rich in B-Vitamins such as beef or chicken liver and heart. Natural Vitamin-Mineral Supplements are also very helpful to boost red blood cell levels. I recommend having your vet check your dogs kidney function by running a complete blood chemistry profile and urinalysis as if there is a lack of kidney function, anemia is a side effect. Herbal remedies such as Parsley, which is high in Vitamin A,B and C and Kombu Broth which is also mineral rich may be a consideration.
for homeopathic remedies I will defer to those who specialize in this area.
For food my recommendation is "the best you can afford". Sometimes the best medicine is not medicine at all - it's food.
I like Hill's Science Diets, IAMS Pro Active Health, Nutro and NutroMax. All my giant breeds have done very very well on these brands.
If your dog needed any special nutritional supplementation, then your veterinarian will prescribe that for you. Today you are seeing may of the top brands add many of these supplements into the commercial brands. Such as Chondrotin, Omega-3 FA's etc.
Learn to read the labels and see how your dogs do on a particular brand. It will not hurt them to try various ones to see which is most tasty and does not cause gas and a normal stool.
This from the FDA: http://www.fda.gov/AnimalVeterinary/ResourcesforYou/ucm047113.htm
A Homeopathic Remedy for anemia is Dang Qui also called Angelina sinensis. This is a traditional chinese blood-tonic herb. Use this at a dosage of 1/4 tsp per 10-15 pounds of body weight divided into 2 daily doses.
Dr Carol Osborne, DVM