Certainly I am sure as a vet he would put them to sleep before they were in pain. But it does state that he had very small dogs and 10 just isn't that old for a small dog
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I do understand waiting til they are more mature too spay, one of the reasons we waited(my vet and I) was in hopes Mignon would gain a little bulk. We did wait, she never did. My hopes now are that she will pick up a little more weight now that she has been spayed. Time will tell.
I would like to add that at 2 and a half lbs her spay and dental went perfectly. The only problems we had was a reaction to her internal stitches and keeping her from jumping up on everything. That might be easier with a small pup.