Dog food you find in the grocery store contains mostly cereals, so this won't do. Some mushers feed their dogs a mixture of meats to keep them stocked up on protein. Mink rations are often used. These consists of chicken, turkey, chicken fat, eggs, and liver. Beaver carcasses are a favorite because of their high fat content.
Some folks use lamb chops, venison and even salmon.
Just like us, dogs love snacks and some lip smackers include honey or fish. Dog food companies have been developing special food for these sled dogs Much of it is high protein mixtures which include pork, chicken, and fish. This heavy dose of protein is rounded out with essential amino acids, digestive enzymes, yogurt with acidolphiles, kelp which is high in minerals, vitamins, and even yucca extract which cuts down on the odor after all this great food has left the other end of the dog. Mushers are required at the start of the race to carry 1 lb. of food per dog. From then on they will depend on the other 12 checkpoints where their handlers are busy thawing, stirring, but probably not sampling the grub.