Well dodged but not.the point at all.
You're advocating killing perfectly healthy dogs many of which are barely teenagers in human terms.
You want to talk numbers not morals or ethics, so you start: how many perfectly healthy dogs killed because they can no longer fulfil a working or sporting role to the highest level is acceptable?
Do you have the same distasteful eugenic attitudes to racehorses, battery hens, retired racing cyclists not making a positive contribution to society?
I am curious. Which post did Tinpost state that he wanted to kill "perfectly healthy dogs"?