The guinea pig plays an important role in the folk culture of many Indigenous South American groups, especially as a food source, but also in folk medicine and in community religious ceremonies.   See Guinea Pigs as Food in Wikipedia.

They make great compost with pellets which - like other herbivore faeces - are enjoyed by chickens, so their wastes can be further cycled in a chicken tractor setting.    Good page here about basic needs.

Eating Guinea Pigs

When Frank Fekonia is feeling a bit hungry he grabs a live Guinea Pig for lunch and turns on the Sandwich Maker. You never ate fast food this fresh!

More videos from this great permaculture designer couple here in YouTube

See some more resources about this in the spanish page of this e-book, also of larger-scale breeding programmes - not permacultural but easily adaptable to be a lot more sustainable.

See the Guinea-Pig Hotel design for one example of a permaculture version of keeping  these wonderful domesticated animals, complete with socio-political analysis article.