  Existing analyzes of baryon semileptonic decays indicate the presence of a
small SU(3) symmetry breaking in hyperon semileptonic decays, but to provide
evidence for SU(3) symmetry breaking, one would need a relation similar to the
Gell-Mann--Okubo (GMO) baryon mass formula which is satisfied to a few
percents, showing evidence for a small SU(3) symmetry breaking effect in the
GMO mass formula. In this talk, I would like to present a similar GMO relation
obtained in a recent work for hyperon semileptonic decay axial vector current
matrix elements. Using these generalized GMO relations for the measured axial
vector current to vector current form factor ratios, it is shown that SU(3)
symmetry breaking in hyperon semileptonic decays is of $5-11%$ and confirms the
validity of the Cabibbo model for hyperon semi-leptonic decays.
