We have studied the cholesterization of discotic and calamitic lyotropic ferronematics by addition of brucine sulphate. The techniques used are optical microscopy for the textures and X-ray diffraction for the structures. The results concerning the pitch and the rotatory power of oriented samples containing or not ferrofluids are discussed in terms of de Vries theory. We have also examined the possibility of micellar deformation by addition of brucine sulphate. Finally, we have studied the hydrodynamic instabilities created in the sample of calamitic ferrocholesteric initially untwisted in a magnetic filed.