Several processes in the early Universe might lead to the formation of primordial black holes with different masses. These black holes would interact with the cosmic plasma through accretion and emission processes. Such interactions might have affected the dynamics of the Universe and generated a considerable amount of entropy. In this paper, we investigate the effects of the presence of primordial black holes on the evolution of the early Universe. We adopt a two-fluid cosmological model with radiation and a primordial black hole gas. The latter is modelled with different initial mass functions taking into account the available constraints over the initial primordial black hole abundances.We find that certain populations with narrow initial mass functions are capable to produce significant changes in the scalefactor and the entropy.Instituto Argentino de RadioastronomíaFacultad de Ciencias Astronómicas y Geofísicas