  We investigate out of equilibrium transport through an orbital Kondo system
realized in a single quantum dot, described by the multiorbital impurity
Anderson model. Shot noise and current are calculated up to the third order in
bias voltage in the particle-hole symmetric case, using the renormalized
perturbation theory. The derived expressions are asymptotically exact at low
energies. The resulting Fano factor of the backscattering current $F_b$ is
expressed in terms of the Wilson ratio $R$ and the orbital degeneracy $N$ as
$F_b =\frac{1 + 9(N-1)(R-1)^2}{1 + 5(N-1)(R-1)^2}$ at zero temperature. Then,
for small Coulomb repulsions $U$, we calculate the Fano factor exactly up to
terms of order $U^5$, and also carry out the numerical renormalization group
calculation for intermediate $U$ in the case of two- and four-fold degeneracy
($N=2,\,4$). As $U$ increases, the charge fluctuation in the dot is suppressed,
and the Fano factor varies rapidly from the noninteracting value $F_b=1$ to the
value in the Kondo limit $F_b=\frac{N+8}{N+4}$, near the crossover region
$U\sim \pi \Gamma$, with the energy scale of the hybridization $\Gamma$.
