It is funny. I did place all 3 pups on the pad and one went and then the other 2 went. They are not trained. This is called conditioning. Do it enough times and it becomes a habit. It means I have to be consistent and you can't be 100% of the time as you are not sitting waiting for wake up time and then running to put them on the pad.
Pups as young as they are never had an issue with the extra space nor looking through the bars. I am proud of them.
I do this to help them and to help you and these are less than 3 weeks old.
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