On a quick search, it seems like aspen wood is considered toxic to degus. I'm not sure whether they'd eat the shavings, but we all know how they love to put their teeth on any new thing, and how they like gnawing anything made of wood...
Generally speaking, my experiences with wood shavings as bedding (not for degus, but generally with rodents) are not great. The shavings can be sharp-edged and I had some rats that developed foot irritation due to it. Additionally, shavings don't absorb well, so they become messy and smelly very quickly.
I used stuff similar to this, and it was fine, not toxic, and aspen makes nice, clean shavings.
We did find that it didn't always do so well with pee puddles, so we would put a very thin layer of coconut fiber substrate, like you use for reptiles, in the bottom, then the aspen chips across that. The reptile substrate would absorb puddles, and the aspen provided a normal type substrate for the cage.
41 liters is about 1.45 cubic feet, or about 10.8 gallons US, or 9 imperial gallons, do you guys have 5 gallon buckets over there? it's a standard size here, so an easy measure to judge things by, would be two full buckets and a bit. Or 20 liter buckets, maybe? would be two of them. And then that's packed tight in the bag, so fluffed up it would be much more.
Perhaps I should take my American butt off to bed and stop typing probably useless information, huh?
Ah, alright, good to hear first-hand information. Looks like there might be some false information about this on the internet then (which isn't all that surprising).
Looking at the video on the site, it actually does mention that it has been kiln-dried and has no phenols, which is the component that was pointed out as toxic in the info I found. So in any case there should be no health hazard there.
About the size of the bag there, 41 liters is quite a bit. When I used shavings for rats or guinea pigs back then, we got smaller bags (they were by weight, so I'm not sure how many liters, but certainly way less than 41), and even those could easily cover a full rabbit cage's floor and have a good amount of shavings left in the bag.
Yeah, that sounds totally doable. You're going through a lot of the stuff, so cutting it with cheaper bedding is a good idea.
What's the bottom of those cages like? One of the reasons I've had to stop using conventional beddings is that the cags I have all have cage bars on the bottom as well (bird cage style), so paper pellets or wood chips would go through and I'd need a lot more of the stuff. So I actually switched to using hay as a bottom material, since it won't fall through. Though I imagine that if the fitch stays in your cage, the shavings would as well.