How to care for underweight rescued puppies to ensure healthy growth?

Awww. It's very nice of you to take on this type of responsibility. The first thing you should do is to take him into the vet for an initial examination. They will be able to make sure there is nothing seriously wrong, versus simply malnutrition and dehydration. If this is the case, Champ will likely require something to eliminate gastrointestinal parasites. He belly looks very round in that picture, which in young dogs is usually associated with worms. This can be a very common cause of weakness and malnutrition, and the nutrients that he is consuming will not be properly absorbed until the parasites are eradicated. The veterinarian will also probably want to give some fluids, either subcutaneously or directly into the bloodstream. The method of delivery will ultimately be decided based upon the level of dehydration the vet detects. Champ will require a healthy, high quality large breed puppy food eventually. However, in the meantime, I would provide something like a Purina Critical Nutrition or HIll's A/D. These are prescription diets that are very high in fat and high calorie, and are typically not easily turned down by even the sickest of pets. Lastly, Champ probably needs your love, warmth and support. I am sure you have plenty of this.

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

Good nutrition and being free of intestinal parasites is the best you can do for their weight. Feed a good commercial puppy diet, and lots of it! You can bathe them to remove any fleas currently on the body before starting a flea preventative. Here is a good chart on aging puppies by looking at their teeth: http://www.ruralareavet.org/PDF/Physical_Exam-How_to_Determine_Age.pdf I would recommend that the puppies be checked out by a vet for their overall health and to see what (if any) intestinal parasites they may have.

Gentle feeding with a high quality, high calorie food such as royal canin gastrointestinal is very effective in regaining body weight and muscle mass. Ensure she is wormed regularly and monitor for any vomiting and diarrhea which may indicate bowel issues

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.

I'm not sure I understand you fully here, but I think you are asking what to give puppies to get their weight up if they have already been weaned from the mom. You really just have to continue giving them puppy food which is high in calories and then treat them for any worms that are present. If there are worms in the puppies system, then their presence is the likely cause for the low weight, so the focus should be on treating the worms. Your vet can test the puppies stool to be sure. Any worm can cause weight loss, including coccidia. I hope this helps and if I did not interpret your question correctly, please feel free to repost to our forum and we will be more than happy to assist you further. Otherwise, best of luck with these puppies moving forward. Take care!

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.