I've got the same problem.
I fully intend, in the future, to grow all my own dog food, through chickens, eggs, rabbits, and vegetables. Plus roadkill, any spare bits of venison that come my way, that sort of thing.
I got an interesting bit of roadkill yesterday, something in the opposite lane had struck this magnificent beast no more than 30 seconds before we rounded the corner, it was still flapping about and feathers floating around in the breeze, but by the time I'd pulled in and ran back to it, it was properly dead. Now if we had been driving the other way, back home after a couple of days camping, I'd be taking it apart carefully and we'd have it for dinner ourselves... probably in a creamy fricassee with mushrooms and white wine... but without the time or inclination on the outward-bound leg of the journey, it was destined for the dogs' dinner instead.
Except... after being quickly peeled, ripped in half, and guts removed (we are on a campsite right now, I didn’t want the dogs throwing feathers and the gooey bits around, scaring the neighbours), the boys sniffed it for a bit, turned to look at me, then walked away.
It's more often than not the case when I give them one of the spare chickens at home, too... it's confusing, and quite frustrating.
They each get a quarter of a raw shop-bought chicken every day, which they destroy with gusto, plus an egg, and they get topped up with cereal as needed. But when I try and give them one of our home-grown birds, they turn their noses up at it until I've poached it gently with a kettle of water in one of their dinner bowls. Which doesn't really gel with my future intentions to grow all of our own dog food.
So anyway, this beautiful free-range guinea fowl, which would have been absolutely freaking delicious, is now sat there ignored by two hungry dogs. I'm going to make a little fire as soon as we get home and throw the carcass onto it, and we'll see if they prefer wood fire roasted pintade fermier instead. But I'm not happy about the situation.