Are nutritional supplements useful for dogs?

A healthy dog's nutritional needs are largely covered by a complete, high-quality complete feed. However, vitamins and minerals in conventional feed are usually contained in synthetic form, which puts a strain on the metabolism. In some cases, such as illness, pregnancy or old age, the nutritional needs are changed or increased. In these cases, nutritional supplements can be a useful addition to daily feeding. When BARFing, supplementary feed can be added specifically to make the food more complete.