The invention relates to a bulk multi-metallic catalyst for hydrotreating heavy oil feeds and to a method for preparing the catalyst. The bulk multi-metallic catalyst is prepared by sulfiding a catalyst precursor having a poorly crystalline structure with disordered stacking layers, with a type IV adsorption-desorption isotherms of nitrogen with a hysteresis starting point value of about 0.35, for a sulfided catalyst that will facilitate the reactant's and product's diffusion in catalytic applications. In another embodiment, the precursor is characterized as having a type H3 hysteresis loop. In a third embodiment, the hysteresis loop is characterized as having a well developed plateau above P/Po of about 0.55. The mesapores of the precursor can be adjustable or tunable.