Hi,
Sorry I've come to this topic late but I don't often look at the forums...
I live in France and I am a committee member for the Normandy Donkey Association which concerns itself solely with 'Anes Normands', a breed recognised in France ( probably the world! ) since 1983. Recently we have come to accept that the major problem genetically for our 'breed' of donkey is that there are not enough animals within the 'breed' constraints to ensure sufficient diversity for the continuation of our 'breed'.
In Normandie there are two 'breeds' of donkey:
the Ane Normand; overall brown in colour with a spinal and transversal cross [St Andrew's Cross], nose, belly and insides of the legs white and russet at the interchange between the colours - and
the Ane Cotentin; overall light grey with the St Andrew's Cross, nose, belly and inside legs lighter.
and both of these 'breeds' in an area of only 11,500 sq miles !!!
Before we humans decided that there are 'breeds' of donkeys, every farm in Normandie had one or two donkeys as a supplement to their draft horses, to do general 'light' work around the farm, similarly throughout the western world before mechanisation. In Normandie some were grey, some were brown BUT THEY ALL worked. Now we try to define 'breeds' ( generally, in my opinion, regional differences ) and to confine breeding within very closely confined limits. As a result, we have consanguinity problems and genetic problems because there are simply not enough donkeys within each 'breed'.
To come back to the original question "Why so many donkey breeds in China while so few in the U.S.?", perhaps because the Chinese have followed our Western example ( in the US more in horses rather than donkeys but the principal stays the same ) and are creating 'breeds' to accentuate regional differences rather than because there are/were different 'breeds of donkey' within a given geographical area.
So the question is really "How to define a separate 'breed' of an animal" and how have the Chinese discovered so many more within their country...
Perhaps it is simply that in the US, four 'breeds' is enough. In France, 7 'breeds' and in Britain,
As a breeder of donkeys ( mainly ane normands!! ) I try to put the emphasis on training and using the animals rather than on their appearance and I respectfully suggest this is the better approach rather than trying to define 'breeds' according to our, human preferences.