Getting him to gain weight/is he underweight?
 

So Harley has been handling the move ALOT better than I have, but he just seems a little underweight to me. (he's so energetic, I'm sure he burns all the fat off he actually gets). He's around 3lbs, I need to get a scale so I know for sure, maybe 3.5 now. So he is a tiny pup, so when I rub his belly, my hand pretty much covers his whole belly, and I can feel ribs. It kind of grosses me out, cause he does have a bit of fat on his chest, but absolutely nothing on the ribs... He eats a lot too.

I just switched him about a month ago to Now! adult, (not the Yorkie one, cause my store doesn't carry it). He used to eat about 1/4 cup maybe a day of the puppy, and now he's eating about 1/2 cup. I fill his bowl twice a day (if needed) and he's free fed throughout the day. He eats most of his kibble at night, or right before I refill his bowl. He also gets Trippet to supplement the kibble. He gets 1/8 of the small cans (probably about a teaspoon), twice a day (morning and night, when I fill his kibble).
He also gets treats daily, either a grain free dental chew (about half of the one designed for a 5lb dog), or canned human grade Altantic Canadian Salmon, with no added sodium or preservatives (ya ya I know he eats better than me, his sitter started that when we moved, so I've been using it as a high reward treat).

So... how do I put a bit of weight on this pup? He'd probably eat more tripe or salmon if I gave it to him, but I'm pretty sure it's the kibble that's going to up his weight properly isn't it? Also... does anyone know of an online (and cheap) dog nutrition course, or a great dog nutrition book... I took a few equine nutrition courses, years ago when I did that, and It made me feel a lot better knowing what to feed... I want to do the same with my little boy.

oh and since the move I've also started walking him outside, and playing a lot more fetch, cause I have more time, and we have a safe place to do so... so his exercise has increased more too.

I feed Now Puppy Formula to my almost 6month old. He was also too skinny, so I increased him to 1/3 cup three times a day. He looks much better now. I don't supplement with anything else. Sometimes raw carrot.

How old is he..is he neutered?
If he has a 3 frame, his weight sounds healthy...better a touch under the over for a Yorkie...many of us think trim is unhealthy.
Some males tend to be thinner...like a teenage boy..eat well and stay thin...if he is healthy and the vet thinks he is fine, I would not be worried..and the chart in the vets office said you should be able to feel the ribs...not padded like they are wearing a coat.

When Woody was llittle I gave him some boiled chicken here and there to keep his weight on. Not as a supplment for food, but as treats. I like to keep him looking 'thick' becuase I don't think he is healthy when he is too skinny. Woody has muscles but being too skinny is no good for Yorkies or People!!

He is neutered, was done at 6 months. I'd up his food, but because he always has access to it, he wouldn't eat any more kibble. So I guess the only way to remotely "fatten" him up is do some training and give him some tasty salmon treats.

I figure he's a decent weight, but I'd prefer him to have a little extra insulation before winter hits. That and I'd love for him to hit a solid 3.5 to 4 lbs when he's full grown.