I was in the supermarket (as you do) .There isn't anything dried foodwise that I buy for the guineas.
They had treats (honey/seed/nut ones) which all the GP forums advice to avoid due to risk of choking, obesity and diabetes.
But they also had egg biscuits, first ingredient listed whole eggs.
They don't eat egg product do they?
. I've never given my GPs egg/egg products.
Maybe ferrets would? (Disclaimer:I know nought about ferrets
)