Thank you for your patience. There are a number of possible causes for your girls apparent lethargy and inappetance this evening, and in a young dog we have to consider everything from an early gastroenteritis, to a GI foreign body, musculoskeletal pain, or even a toxicity (hopefully there isn't anything she could have gotten in to in your home or around your yard). You are certainly going to need to continue to keep a close eye on her, and if she continues to seem quite lethargic and won't eat anything, then you will need to get her along to your local ER vet this evening. Make sure she has plenty of fresh water available and try to encourage her to have a good drink now if you can.
For now, please keep an eye on her mucus membranes, capillary refill time and respiratory rate tonight as follows (do be careful that your girl doesn't try to bite you):
Mucus membranes - flip her lip and look at the color of her gums. They should maintain a nice salmon pink color. Get her to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on her gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.
Respiratory Rate - if she seems to be panting or breathing rapidly throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
Best of luck with your girl and hopefully she perks up soon. If you think this could be due to abdominal pain, you may also want to try her with a little pepcid. The typical dose for this type of situation is 0.25mg per pound of body weight up to twice daily. You can read more about the use of Pepcid in dogs online here: http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid
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