It’s best to keep the jenny and jack separated until the foal is weaned. After the foal is weaned, don’t run it loose with the jack. If it’s a jenny, he will try to breed her. If it’s another jack, they’ll fight. It’s best to let your jack live separately unless you want to breed him, and overall, it’s best not to keep a male donkey intact unless he is a valuable, pedigreed animal and you are able to handle and house him just as you would a horse stallion.