My Dog Is A Mixed Breed Border Collie-12 Years Old.

My dog is a mixed breed border collie-12 years old. Just recently she looks at her dry dog food, smells it and walks away. This is a dog that would eat her dog food so fast I could hardly get it in the bowl fast enough. She acts like her teeth/mouth might hurt her. Also, the gait in her hind legs looks different and she doesn't; seem to have much energy. I took her to my vet last week and blood work turned out fine. I plan on getting x rays next week.