Complementary pet food is legally defined as food for pets that is high in certain substances but is only adequate for a daily diet when used in combination with other pet foods. (
FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs p.32 // FEDIAF Nutritional Guidelines for Complete and Complementary Feeds for Domestic Cats and Dogs p.32)
Complementary pet food covers a wide range of products, including:
a. Foods that significantly add energy to the daily diet
b. Products designed to be mixed with other foods, adding individual ingredients to complete nutrition for the dog
c. Treats and snacks usually given to strengthen the human-animal bond and as a reward during training. While they are not intended to be a complete feed, they can be fed in amounts that affect overall energy expenditure.
(Article 3, 2j, Regulation (EC)
No 767/2009 of the European Parliament and of the Council of 13 July 2009 on the placing on the market and use of feed // Article 3, 2j EC Regulation
No 767/2009 of the European Parliament and the Council of 13 July 2009 on the placing on the market and use of feed)