Thiocyanate-ions are ubiquitous in living nature. They are important for the cell-function and the ongoing of vital functions. Therefore they are an essential factor in both, animal and human being. The Thiocyanate-ions are brought in alimentary but also built by the organism itself. Beneath the guarantee for many different body-functions Thiocyanate-ions are an important part of the immune response. To that belongs their involvement in H2O2-Thiocyanate Peroxidase-Systems. Furthermore Thiocyanate-ions are agents for cell-protection and for the repair-mechanism of the host in the struggle with toxic substances of germs. Therefore they also have a tumour-prophylactic effect. Thiocyanate-ions participate at physiochemical reactions which due the protein-conformation. There are hypothesis that a deficiency of Thiocyanate-ions may be a co-factor for causative agents of diseases such as Cystic Fibrosis and Transmissible Spongiform Encephalopathia. References for calculations of the alimentary balance are given, if deficiency of Thiocyanate-ions occurs. From the view of an optimal animal-feeding the sufficient alimentary supply of Thiocyanate-ions and their precursors is mentioned.