Would grass stay fresh for long after picking?

[Shalom]

Had a lovely day out in the glorious Berkshire countryside yesterday, my husband thought I was mad when I filled a dog poop scoop bag with lovely lush green grass!
What I want to know is how long can you keep a bag of grass for the guinea pigs? Must it be eaten on the same day or can it be saved for next day or even the day after, I think grass ferments, not sure what the ruling is on this so can somebody help, thanks.
Also I read on here the other day that outdoor guinea pigs like to eat maize as it helps to keep them warm, is it possible to obtain just Maize so I could add a bit to their nuggets ( they eat Pets at Home nuggets)

 

[AndreaJane]

I would chuck it out after a couple of hours but that's just my personal opinion.

 

[AndreaJane]

And for those couple of hours I'd keep it in the fridge or a coolbox if I'm out. Did you make sure you were in an area that wouldn't be sprayed with pesticides, fertilizers or fouled by animals?

 

[Little Pig]

Make sure the grass is clean and dry and pop it in the fridge. I think it can last for at least a day that way, but not really any longer.

 

[Dindypig]

I keep mine in the fridge loose and dryish in a carrier bag, lasts about as long as a bag of mixed lettuce leaves.