My Sport is also very picky and is not super food-motivated. Right now we are on the Royal Canin YT puppy (forget the number) which he used to like but about a month ago he just stopped eating it so I have to think about my next move in terms of kibble.
Right now he is on a mix of Stella & Chewy's Super Beef Dinner and Puppy Plate (canned) turkey & sweet potatoes. I give him half a patty of the S&C and I run a little warm water into it to make it moist. I also place a few drops of Grizzly Oil (fish oil supplement for dogs) on top which he seems to love. He normally gobbles at least some of this up right away. On rare occasions he even polishes off the whole bowl!
In addition he gets 1/4 can of Puppy Plate per day.
I feed everything in the morning and leave it for him with fresh ice water thoughout the day. He usually eats a little when it first goes down, then picks at it throughout the day. Normally I do throw some leftovers away the following morning.
If your guy needs to gain weight, have you tried Tomlyn Nutri-Cal Puppy? When Sport was young, I gave him about 2 tsp of this a day (once in the morning and once at night) and he LOVED it. He still loves it actually. I mainly use it as a training treat now or to get him to take pills. He GOBBLES it up and I like knowing he is getting the calories. And I guess it has worked pretty well since he is the correct weight for his age/length.
