I have a smooth-haired dachshund. I've had it since it was 6 weeks old. It was nice and small (like any other puppy). But then when it got older, it didn't grow tall, it just kept on growing longer and longer. Right now he measures 7 inches tall by 22 inches long. What should I do? Should I take it to have length-reduction surgery? Back surgery? Should I feed it more? It walks/runs funny, too.

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I would say that it probably is a little abnormal but not to worry too much.
I would however take precautions. Dachschunds are known for jumping off of couches and injuring their backs due to their proportions. I would say it's even more likely to happen with your dog. Get either step up or stack some clocks on any furniture your pup might jump off of.