Substances contained in the fruit of Milk Thistle (Silybum marianum) may in most cases help eliminate these unfavourable influences. In particular the substances of flavonolignan nature that are isolated in human medicine as a high concentrate called silymarin are able to take significant part in regeneration and protective processes in liver. They increase cholepoiesis (choleretic effect), support its secretion (cholagogic effect), and mainly they are able to protect liver against toxic effects of various organic substances causing so-called oxidative stress, or even against heavy metals. As all substances from the group of flavonoids, flavonolignans act as strong antioxidants everywhere in the organism and thus participate in its protection against free radicals and other substances, long-term effects of which may lead in particular to serious and permanent damage of the organism.

In addition to flavonolignans and other substances of flavonoid nature, fruits of Milk Thistle contain also vegetable oil with high content of linolic acid. This multiply saturated fatty acid ranks among socalled essential fatty acids, which mammals get from feed. This acid belongs to the group of omega-6 fatty acids that are very important for many metabolic processes in mammals‘ body. Essential fatty acids participate in development of cell membranes, and they are basic substances for biosynthesis of important mediators, such as prostaglandins, prostacyclins and leucotrienes that control and influence inflammatory processes in the organism as well as its other functions. Deficiency of essential fatty acids in animal feed may cause development of serious metabolic disorders.

In terms of legislation, there is an important approach of the European Commission to flavolignan effects in the area of veterinary medicine that is included in the following directive: Committee for veterinary medicinal products EMEA/MRL/665/99.