
I'd hold off bottling them because mum 'should' be producing milk depending on the demand.... in other words if the puppies don't feed from her as much as they might if they are being bottle fed too, this may be counter-productive. Of course IF there is a big litter, it's often necessary to supplement, half on, half off. Are the puppies gaining well when you daily weigh them - and are they quiet after feeding because this should usually be your guide re the need to bottle feed.
The only real benefit with tube feeding vs bottling is it's less time-consuming. Obviously puppies can be bottle fed from birth, and would be if something dire happens to hum.