Female donkeys enter into heat at 8 to 12 months of age. Receptivity occurs when the jenny backs up to the jack, or male donkey. In order for the jack to achieve a full erection, the jenny must kick the jack in the face for several minutes.
Female donkeys have a 21 to 28 day estrus cycle, and mating is often accomplished through hand and pasture breeding. Female donkeys have similar reproductive systems to horses, but donkeys are far more fertile.
Foals, baby donkeys, walk within the first hour of birth. However, foals are unable to eat adult foods, such as grass or grain, until one month. By four months, they are mature enough to completely switch from their mother's milk to an independent diet.
By 12 months, donkeys are independent and similar to human teenagers. At 2 years of age, donkeys assume adult proportions in the body and legs. Breeding is not recommended until the donkey is mature enough to withstand the birthing process.