So I feed Malone either Victor High Pro Plus or Diamond Extreme Athlete along with canned food and calorie supplements... And he still stays fairly thin. He has no parasites and is healthy as far as vet can tell... He is just very high energy and high metabolism. When I was feeding him just regular dry food - he turned into a BONE! Very underweight... Trying to work out a possibly less EXPENSIVE way to keep him at a healthy weight. I think he looks pretty good right now... But boy keeping the weight on isn't easy.
My Moose-dog was like that. For the first 4 years, he was eating 5-1/2 cups of food per day just to maintain his weight. Standard quantity for his size was 3 cups per day. Anything less and his ribs would protude halfway til his next mealtime. He was just very high metabolism. At about 4, his metabolism leveled out and he went down to 3-1/2 cups of food per day. He was always thin but a healthy thin. He ate that amount til he died at 15 and never got heavy. I would adjust his food amount to maintain a weight rather than use supplements - as long as he isn't getting fat, more food won't hurt him. But supplements can be questionable. You may want to feed him several meals throughout the day rather than one or two meals. You could try a puppy food. From the photos, he looks good. You don't mention his age or breed(s). Those can have a lot to do with his figure.
He is about 2 years old now. He is a mixed breed of a thousand different breeds 20% pit bull 15% labrador 15% cocker spaniel and a bunch of other MUTT. He doesn't eat well tho... He will PICK at food oftentimes. Dry food is often just left there usually. No way can I get 5 cups of food down him. Never. The Dyne liquid in particular really helps him eat better. He currently looks okay - slim but not THIN/BONY.
Moose-dog picked. Have you tried just adding a bit of wet food and water to the dry? And again, try smaller and more frequent meals.
I work 12 hour shifts 5 days per week with a 1 hour commute each way. I am not home to feed him multiple smaller meals. A family member will let them (Malone and my other dog) out a few times when I am gone, but they are not going to feed him etc. So I have to do what works. He does not like water added to his food. He will eat a LITTLE better with canned added. But he eats a LOT better with the calorie syrups added. If his weight will hold, I will just keep doing what I am doing. It is a bit pricey. I don't even like to feed my dogs canned food, but he is so picky that I feel I have to or he turns into a malnourished looking rat. Edited to add that he is about 50 lbs and does not eat a lot. Doesn't matter how good the food is... He will not eat more than a a cup and a half or so of food plus a can at a time. The bowl is just left unfinished. He can't eat a lot.
My first Akita was really picky. I’d mix in canned food and he still wouldn’t eat it all. Eventually he became less picky and I didn’t need to add canned food. I don’t remember what age he was when that changed. I’m sure you’ve tried all sorts off different brands of kibble.
The other dog is fat and he eats what I find on sale so I always let Malone try it... He picks over all kibble and flat out won't touch some of it. But he will eat better with an entire can mixed in. He eats all of it with calorie syrup added.