Did not know that, but years ago the envelopes the tacos come in had a very small Purina logo on them.

Side note, years before I had a JITB taco, circa 1969, I had identical ones at the snack shack at the community college pool where I took swimming lessons. Years later, when taking classes at another JC, they had the same exact tacos in the cafeteria and sold zillions of them.