When you say his tail "has lost its curl," do you mean that he used to curl it and wag it, but he doesn't do that anymore? That sounds like an injury, and I would take him to the vet. Dogs can even get their tails broken.
Sometimes as our babies age they dont seem to lift there tails up on there back as much as they did when they are younger.And i have seen some that just dont lift there tails at all.Also as they had stated in other post it could very well be an injury,Is there any areas in his tail that looks like it could be broke.There is really no treatment as far as repairing a broke tail,But if that is the problem atleast you would have an answer as to what is wrong.My Peke broke her tail and i didnt even know until i was grooming her one day.My vet told me that there was nothing that he cold do to fix it.Well let us know how he is doing .
Please take your dog to the vet. My (show quality--although never shown) chihuahua walks with her tail up and prances like a Clydesdale horse--interesting for a 3 1/2 lb chihuahua. All I could tell the vet was that her tail was now down between her legs when she walked. He watched her walk and diagnoised rup. discs in her back which was confirmed by X-ray. He put her on pain medication and unlike humans--they fuse back together and heal BUT if this is the problem it Will probably happen again--if you have a great vet like mine--he will save you the money of the X-rays and just give you the pain medication when it happens again. Hope this helps.
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