To be honest, I think this part is somewhat self-defeating:
But how to best utilize a forest for animal husbandry, in the way that hopefully interferes with wild nature as little as possible?
From a permaculture perspective the goal isn't to avoid interfering with nature, but to try to ensure that interference is constructive. In other words, ecosystems are steered towards productive uses by our standards rather subtly instead of using force of effort to the detriment of everything. Ecosystems are co-evolved so let's try to be part of that coevolution. So having reframed the question that way, here are some thoughts about utilizing what is there:
Many kinds of trees can be utilized as fodder. If you watch your animals you can see what they like to eat and a pruning saw (and a pair of loppers) can be used to retrieve some extra food from a bit higher than your animals can reach.
The animal manure can help recycle nutrients in the natural ecosystem.
The edges of the forests are likely to be the most productive in this way.
Here are some thoughts about hazards:
Many kinds of grazing animals will prevent new edible trees from becoming established. It is probably a good idea to plan to protect some areas for new trees from time to time.
Overgrazing may also damage undergrowth in undesirable ways. Again the problem here is overgrazing.
Now some thoughts specifically about boreal forests:
These are mostly conifer forests. This means that to the extent animals can graze on trees, they will be pines, firs, and the like. This is not out of the question but it may mean something for animal selection.