Overly frequent deworming also promotes resistance. Due to the increasing resistance to deworming medications, alternative methods of parasite control are being sought. In recent years, greater attention has been paid to secondary plant compounds. Condensed tannins are said to have a direct effect on parasites. Traditional knowledge attributes immune-stimulating and anthelmintic properties to certain plants. Research in recent years has increasingly focused on secondary plant compounds. Comparing the plant life of an unfertilized meadow with that of a conventionally managed meadow, one finds significantly more and more diverse species of wild grasses and perennials on the latter. Many of these are well-known medicinal plants. Consequently, ruminants today lack the plants and secondary compounds essential for their digestion. One commercially available supplementary feed consists of herbs and spices. This mixture is intended to boost the animals' overall immune system and enable them to better cope with parasites.