Sometimes their feathers can grow in goofy,but as long as the wing is laying flat against the body there is not a problem. Sebastopol geese are prone to wing defects due to mutated feathers. I have some 4 and 5 year olds with perfect wings and others can have 1 wing effected by twisted wing tip and some with both. It is a very hard thing to get away from.Smooth breasted bird rarely have wing troubles. Young ones can also have stiff flights until they molt out. My geese are on a Turkey starter, mix with black oil sunflower seeds, whole oats , milo . Sounds like they are eating well and grazing on fresh grass is always the best and with your guardian livestock dog it sounds like they are well protected. I am sure they love being able to share the dog food with your dog as mine love it to.