The invention relates to the production of proteins, peptides and other substances of interest in the saliva of transgenic animals, particularly in mammals that produce large quantities of saliva, particularly monogastric ruminants, and ovine, caprine and bovine mammals. Preferred embodiments of the invention relate in particular to the production of foreign and modified proteins in the saliva of these transgenic animals, including particularly human serum albumin, human Protein C, human Factor IX, human factor VII, human Factor VIII and human von Willebrand factor, among others. Also provided are methods of expressing and producing proteins using such nucleic acid constructs. The invention relates as well to methods, devices, genetic constructs and to transgenic constructs for making the proteins and other substances of interest, to novel saliva and saliva-derived compositions, novel products produced from the saliva, and to uses of the saliva, saliva-derived compositions and novel products.