if they will stop eating oxbow or other pellets there is nothing to fear of... your piggies will live as well as before just like mine who have some pieces of pellets only as a treat (and not every day).
In our shops there are the usual international brands, depending on the store. There is Oxbow (I don't like its composition; it has wheat, flour and such ingredients alter the good bacteria in the gut), there is Versele Laga, Bunny, english brands and other ones. Here many people buy online, there is a greater choice and cheaper prices.
You say that Oxbow is so good: there is a label on the side of the box made of numbers of percentages of single nutricional values (proteins, fats, ashes, etc). Make a sum of all those number and tell me what number you get. Is it 100%? NO. It is 44-48% only. What is the other 52-54% component made of? why don't they declare it?
(it is sugars from starch, polysaccarides, etc... substances which are bad for guinea pigs)
I have at home Versele Laga Complete, it looks better than Oxbow because it is grain free, but I don't trust any dried food.
if you are interested, there is an interesting experiment made in Germany
https://translate.google.com/transl.../www.diebrain.de/nh-versuchtrockenfutter.html
https://translate.google.com/transl.../www.diebrain.de/nh-versuchtrockenfutter.html
this is an abstract:
Experimental setup and implementation
The following feed samples were used for the experiment:
Sample 1: 5 g Finely structured, hot-pressed * feed pellets with additives (cereals, molasses, etc.).
Sample 2: 5 g Coarse-textured, cold-pressed * meadowgrass pellets without additives.
Sample 3: 2.5 g Dried vegetable granules (parsnip, carrot, beetroot).
Result
After 6 hours, all samples were lightly expressed in a sieve. The samples then dripped off for 10 minutes. Then they were weighed.
Sample 1: feed pellets / the mass is very fine and crumbly.
From 5 g of dry matter 25 g
Sample 2: Meadow grass pellets / the mass is elastic and clumpy.
From 5 g of dry matter 23 g
Sample 3: Vegetable granules / vegetable pieces are elastic and still firm.
From 2.5 g, 13 g (5 g = 26 g)
Each sample has absorbed a lot of water within a short time and all samples have at least tripled their volume. The overall visual impression has shown that pellets look like little food but have a massive weight. At estimated equal volume, the dry vegetables weighed only about half.
Conclusion
The experiment, like many similar experiments before it, has once again shown that pellets and dry vegetables swell strongly at the recommended extra water intake in the digestive tract. Since they are usually only chewed for a short time and eaten in large quantities in a short time due to their compact form, however, the satiety feeling in the animal only sets in after the intake of many pellets / dry vegetables and only after the onset of the swelling process. Due to the pellet components, which swell only later, the stomach walls are heavily loaded, the animal eats a lot more than it tolerates, because the satiety begins too late. The animal is then extremely fed and does not eat for a long period of time, a uniform feed intake is no longer guaranteed. Without water, these feeds drain the needed fluids from the digestive tract and make digestion difficult, leading to constipation and other intestinal problems. In addition, it leads to a reduced urine output, which in turn increases the mineral deposits in the bladder and kidney, as the minerals are flushed out only by high fluid delivery through the kidneys and not through the intestine.
These feeds should only be offered very rarely and in small quantities!
Small amounts of pellets and dried vegetables can be offered as a caregiver if the animals need a lot of energy (eg in the winter outcrop). However, it should never be full food trays in the enclosure, since then there is the risk of gastric overload and excessive feed intake (and thus weight gain).
https://translate.google.com/transl.../www.diebrain.de/nh-versuchtrockenfutter.html
Hence, if your piggies will stop eating pellets you will save money at the store and maybe with the vet 
