Do you keep male donkeys separate from pregnant donkeys?
You should, to ensure that the male (if he is intact) will not try to mate with the Jenny. Some donkeys and horses are aggressive to the females while mating.
No, not all donkeys are female. There are both male and female donkeys. Donkeys reproduce by breeding with other donkeys. Mules and hinnies are a cross breed between donkeys and horses. If you breed a female horse and a male donkey, you get a mule. If you breed a female donkey and a male horse, you get a hinny.