Guide dogs work daily and need quality nutrients to remain alert, bright and healthy. Standard department store brands of food just don't cut the mustard. Quality foods such as Iams, Science Diet, Purina Pro are examples of quality dog foods. These foods are easily digested and have a very rare chance of causing gastric distress. Animal foods should be chosen with the health consciousness as we ourselves pick our own foods.
Some guide dogs are on vitamin supplements.
Iams, for example has been proven to be so completely balanced that vitamins are not necessary. Another big essential is clean drinking water. Dogs like people need fluid. And while they can not drink Pepsi and Mt. Dew's they can drink plenty of water. This is especially true in hotter climates such as the south and the mid west.