First, I am glad to hear that Simba hasn't any of those signs I asked about, as that makes a blockage from something he ate less likely here. Though I would note that the lapse of appetite after vomiting for a bit is a very common signs of a dog still being nauseous (where they avoid eating to avoid the risk of vomiting). Therefore, we need to tread with care. As well, the limping doesn't fit but if he hasn't had a proper meal for a good few days, its possible he has managed to strain/sprain something. So, we'd want to rest that leg just now as we tackle his anorexia.
Now based on the signs we are seeing, we do have a few concerns. The sock sounds to be a red herring and instead we'd need to consider include bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections or another GI irritating ingestion.
With this all in mind, as long as he can keep water down, we can try some home supportive care to try to settle his stomach. To start, if he hasn’t just vomited (since otherwise we’d need to rest his stomach for a few hours first), then you can consider treating him with an antacid. Common OTC pet safe options would be Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet). Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned. Though I'd note that if you give this and he cannot keep it down due to nausea that is usually a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.
Once that has had time to absorb and he is steadier on his stomach, you can consider starting him on a light/easily digestible diet. Examples you can use are cooked white rice with boiled chicken, boiled white fish, cottage cheese, or scrambled eggs (made with water and not milk). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. Though if he cannot be tempted and since Simba isn't vomiting, we'd want to consider syringe feeding at this point. To do so, we can use watered down calorie rich diet like Hill's A/D, Royal Canin Recovery or even canned puppy food. As well, there are also liquid diets like Clinicare Canine/Feline Liquid Diet or Dogsure. And there are paste formulations (ie Nutrical) that can also be of benefit. All of these are nutrient dense, so a little goes a long way nutrition-wise. And these could just help get some more calories in even if we can’t get a huge volume of food in.
Overall, there are a wide range of agents could trigger this anorexia. In this case, a foreign body is less likely but we do have other concerns for these signs. So, we’d want to start supportive care to settle his stomach. If he cannot keep that or water down at any point, appears dehydrated already, or doesn’t respond to the above within 12-24 hours (since this has been going on longer then ideal for a young dog); then we'd want to get his vet involved. They can assess his hydration, rule out fever, make sure there is nothing in his stomach that shouldn't be there or any sinister viruses present. Depending on their findings, his vet can treat him with injectable anti-vomiting medication, appetite simulants, +/- antibiotics to settle his stomach, and get him back feeling like himself.
Please take care,
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