  We investigate the effect of the presence of non-pure fermionic neutrinos on
the relativistic effective degrees of freedom in the early universe. The
statistics of neutrinos is transformed continuously from Fermi-Dirac to
Maxwell-Boltzmann statistics. We find that the relativistic degrees of freedom
decreases with the deviation from pure Fermi-Dirac statistics of neutrinos if
there are constant and large lepton asymmetries. Additionally, we confirm that
the change of the statistics of neutrinos from Fermi-Dirac to Maxwell-Boltzmann
is not sufficient to cover the excess of the effective number of neutrinos.
