Does anyone know why it is not wise for a  bitch to have her first litter after 5 years old?

Its the same reason a woman shouldn't have her first baby at 45 ;)

I don't know if this is the case in dogs, BUT in many other animals (not all) after a certain age the pelvic bones will fuse in position if they have not given birth, so giving birth becomes virtually impossible as the bones cannot separate enough. (Would be interested if anyone know if this is the case in dogs!)

we had a litter from an older bitch as she was really immature and we waited for her to mature more and be calmer, i dont recommend it as it was her first litter, she had to have a cesar and then wouldnt look after the pups, it was a hard slog, i really wish we had done it sooner rather than later, as we may have avoided all the problems we had!  we were lucky as mum and pups all came through ok.

definatley wouldnt recommend doing it!

yes - it is all to do with the fusing of the pelvic bones in dogs too I believe

Cheers! :)

My bitch Miranda was over 5 for her first litter and had 14 puppies without any help other than an Oxytocin injection near the end just to stimulate some contractions & boy did that work, 3 born in the back of my car just in the space of 10 miles!