Reproduction Jennets can become fertile at one year of age but if bred, make very poor mothers and usually reject their foals. Miniature Donkeys, on average, carry a foal for 12 months. Most are not bred again until their second heat cycle, some 30 odd days after foaling. Some jennets will not conceive until their foal is weaned. Taking all into consideration, the average jennet produces one offspring every 13 to 14 months.
Jacks inherit much of their overall fertility and libido from their sires.
Twinning in Miniature Donkeys is rare. Birth weights are generally between 18 and 25 pounds. Smaller jennets may need human intervention.