How to safely put weight on my underweight rescued dog without overfeeding?

Well done on making such progress! Be sure to keep him dewormed monthly for at least 3 months and feed him up gradually, I would tend to feed at the feeding guideline for his actual weight plus 15-20%, reassessed every 14days in order to encourage gradual weight gain and strength whilst allowing his system to adjust. A probiotic/fiber supplement such as fortiflora can be helpful to promote healthy digestive balance also

You should treat him for intestinal worms to start with as this condition can prevent him from gaining any weight, if this doesn't help try feeding him 3 times a day with a high quality food such as Acana for example.

Hi and thanks for posting on Petco Pet Education Center, formerly Petcoach! If he is rescue, he may not have been eating as much every day as he should which is why is a little thin. Now that he is in good hands, feeding him a good quality dog food formula (I'd go with Hill's, Science Diet, or Royal Canin) will help put weight on him. It is hard to say what Eddie's ideal weight should be without seeing Eddie in person. I would have him evaluated by his veterinarian to assess how many calories he should be receiving every day so you know how many cups to give per day. I hope this helps!

Getting her spayed would definitely be the most effective and easiest way, if this isn't something you would consider then i would recommend switching to a better quality food such as Orijen, Acana or Taste of the wild.

If you can’t increase the volume of food the pups will eat, try to increase the calorie content. Also making sure you feed a high quality food will ensure that the pups absorb the nutrients appropriately. I like Royal Canin and Purina Pro Plan. You will find information about the calories on the side of the package. They are called Kcalories in dog food. I hope this is helpful and please feel free to post any additional questions.

There is not much you can do other than to ensure good nutrition and health from this moment forward. I would recommend starting a high quality puppy food. In addition you want to make sure that they are up to date on vaccines per your veterinarian. They should be dewormed at least twice. Finally, you should endure they are on flea prevention and heartwo preventative if endemic in your area. All of these things should improve their overall condition. I also recommend neutering between 6-8 months. Good luck!

If she is underweight she may have an underlying medical condition. I suggest you have her examined by a vet. That is big weight discrepancy. Be sure you are feeding her a high quality food like Royal Canin puppy and be sure she has been properly dewormed. You can also try this supplement. ( https://jawsnpaws.in/pet-mankind-aptiquik.html ) Hope this helps. Best wishes.