  Pade-approximant treatments of the known terms of the QCD $\beta$-function
are seen to develop possible infrared fixed point structure only if the number
of fermion flavours is sufficiently large. This flavour threshold is seen to be
between six and nine flavours, depending upon both the specific choice of
approximant as well as on the presently-unknown five-loop $\beta$-function
contribution. Below this flavour threshold, Pade approximants based upon the
QCD $\beta$-function manifest the same infrared attractor structure as that
which characterizes the exact NSVZ $\beta$-function of supersymmetric
gluodynamics. Such infrared attractor structure is also seen to characterize
Pade-approximant treatments of vector SU(N) gauge theory in the large $N$
limit, suggesting common infrared dynamics for the strong and weak phases of
this theory.
