  An exact numerical calculation of neutrino emissivity of two and three
flavour quark matter have been carried out. We find that the neutrino
emissivity obtained from the Iwamoto formula is in qualitative agreement with
our calculation for two flavour quark matter. For three flavour case, on the
other hand we find that the Iwamoto formula overestimates the numerical values
by $\sim$2 orders of magnitude or more for d decay and agrees with the s decay
results within a factor of 3-4. The dependence of the emissivity on
temperature, strong coupling constant and baryon density is also quite
different from the Iwamoto formula.
