is it the dog or bitch that detemines the amount of puppies

it's the number of eggs that the bitch produces that determines the number of puppies, but the dog can have an impact if the sperm isn't very good.

many more eggs are likely to be fertilised than pups born as the fertilised eggs have to implant in a good place in the uterus and develop an efficient placenta.

So primarily it is the bitch that determines numbers unless as said the Male is sub fertile.

I have always believed (not set in stone) that numbers are decided by the bitch, and sex of pups decided by the sire.

Jean, I believed that too.  Same as humans.

funny you should say thet as my boy used twice has sired 3 bitches 1 dog on 2 seperate bitches

it's often swayed by the timing of matings - and how long the sperm has to 'hang around' for the eggs.. sperm for girls has more staying power :-) didn't work with one of my litters where we had early matings but only 1 girl... but it apparently has some impact