Berries

Various berries as food items (similar to eggs).
"In Europe, wolves eat apples, pears, figs, melons, berries and cherries. In North America, wolves eat blueberries and raspberries. (...) They are known to eat the berries of mountain-ash, lily of the valley, bilberries, cowberries, European black nightshade, grain crops, and the shoots of reeds." © Wikipedia

Support! Fruits and berries also tend to last longer than raw meat so maybe a benefit of these items would be them lasting a few days longer than meat.

As for obtaining them, maybe some new Encounters and herbalists being able to find them while foraging?

I was just thinking of something similar, but applied to plants more generally so you could choose to use some of your herbs as food in a pinch. I thought they should only fill 5% hunger though. Some herbs that already exist are edible (bear berry, buffalo berry, dandelion) and they do keep longer than meat so it might be a good thing to have stocked up for hard times.

New plants/herbs as food would be interesting.

Edit: maybe your herbalist would have to learn which are edible and which aren't? Especially if it's something that's not immediately obvious like blackberries or apples. Garlic will kill dogs and cats, and while birds and rodents can eat the berries of burning bush it will sicken other animals.

Support!

Simply put, this would be cool and would potentially add a few more food options out there. 

As soft_descent said above, maybe instead of your hunting party finding these foods, the herbalist has a chance of bringing some additional berries back with them?

Otherwise, maybe this can be a "task" for adolescent herbalist mentees -- go out and scavenge lol.

I really like Evil's idea, it would be a really cool job for the herbalist apprentices to do! Maybe the berries could come in a 'vine' or something similar. It would function like a stack, with 4-10 berries per vine. Each berry could be used separately or the whole vine could be given to one wolf.