The quote here is a reference to the old JRA commercials to commemorate certain horses and promote races.

Like all other quotes before this, this one is pretty self explanatory. Mejiro McQueen just won so much, for so long, and was always so healthy. She was indirectly bred with a legendary hot headed horse, in hopes of getting offspring with legendary ability, but with the calmness and health of McQueen. Instead, they got a line of big, hot headed horses with legendary abilities (Stay Gold, Gold Ship, Orfevre, Oju Chosan). Oh well, at least they're healthy.