Ask ten different breeders about what to feed your Dane and you will get ten different answers! Feeding Danes, especially puppies, seems to be a highly individual matter. What works for one breeder may not work for another. However, you will find that breeders and vets familiar with the breed will agree on certain items.
Great Danes should be fed with a good quality food, that is no more than 23% protein and no less than 12% fat to Danes of ALL ages. The amount your Dane will eat will vary greatly, depending on age, life style, activity level and health. A Dane should never be rib-skinny. The back, ribs, and hip bones should be covered. They should be fed 3-4 times daily as pups, decreasing to 2-3 times a day at around age 6 months. Dogs (males) will often eat more than bitches. Also, be sure that the dog has not exercised for at least 30 minutes before eating and do not exercise it for one and one-half to two hours after eating. This will make sure it's stomach is settled during the critical time around the meal during which it is very susceptible to bloat.
Danes should be fed in stainless steel dishes raised off of the floor, adjusted at their chin or chest level.
Supplementation of Danes' food is discouraged, although there are exceptions. The two exceptions I know about are vitamins C and E.
Calcium supplementation is to be avoided, along with most other minerals. Some vets tend to believe that just because these dogs get so big, their body needs extra calcium to build bones. But modern foods are balanced to provide the necessary level of calcium, and additional calcium could contribute to bone problems and bloat. Other minerals, such as phosperous may contribute to growing disorders such as Wobblers, if supplemented.
Some breeders believe that high doses of Vitamin C may prevent the incidence of growing disorders, such as hip displaysia. The dosage is 1000 mg - 2000 mg per day of a Vitamin C salt. As excess Vitamin C is excreted in the urine, it is unlikely that this supplementation can do any harm.
Vitamin E is often used as a preservative now, and is considered safer than other chemical preservatives, such as Ethoxyquin. Vitamin E is though to lead to a healthier coat. Foods that do not include Vitamin E may be supplemented.
The addition of wheat germ oil or a vegetable oil to the food will also help to maintain a nice hair coat. Dry dog food does not contain enough fat for the coat and usually supplementation is needed.