Dry Cat food (8–10% moisture) is generally made by extrusion cooking under high heat and pressure.
Fat may then be sprayed on the food to increase palatability, and other minor ingredients, such as heat-sensitive vitamins, which would be destroyed in the extrusion process, may be added.
Dry food is most often packed in multi-wall paper bags, sometimes with a plastic film layer; similar bag styles with film laminates or coextrusions are also used.
Yes, if they manage to get a nibble of dry cat food they will be fine. It won’t do them any harm.
However, it shouldn’t be fed purposely to them. It holds no nutritional benefit for them at all and is not recommended to be fed to guinea pigs.
For more foods that guinea pigs can and can eat check out our GUINEA PIG FOOD LIST