OK, this is def. my area of expertece...

If the rats have any definciencies they dont normally eat thier young. And, they dont usually eat their young for over crowding..your most likey reason they ate some of thier young and not all is cause something was wrong with them. Rats (rodents) in general think in terms of "the fittest servive".. they may have looked healthy to you, but, there may have been something wrong with them so the mothers dipatched them knowing that they were prob. gonna die anyhow. Also, I have seen rats do this when they are having too big of litters. So the mother may have felt she could not have cared for them being there were so many. I would not worry about it too much, it does happen sometimes. If your rats were over crowded, they would have eaten the whole lot of them, not just a few. Hmm, also on the note of "chinese rats", I have bred rats for many years... I have never heard of such a creature. However there are only a couple of other "rat" species, and chinese is not one of them. I had run my rattery and bred rats for show/pet/feeders for a long time, and was very successful business wise and well known to those who bought rats for show purpose and for pets esp. , so I do have alot of experience with rats and many other rodents since rats are not all I bred. I know alot of the genetics/disorders that are common..etc. Hope this helps.