We've had a total of 3 mini Donks over the years.... 2 Geldings (brothers) and currently 1 Jenny. All have been gentle. Our Jenny has been the noisiest of the 3 and also the friendliest. We incorporated all of them in with our horses without a problem. Ella, the Jenny, came to us when a miniature horse owner we were acquainted with here in Oregon was making a job related move to the East Coast and was limited with how many "livestock" she could have. No one wanted to buy her! So, we agreed to take her.
Ella has been a gem. Very easy going, an easy keeper, and very willing to be lead lined with a youngster on her back. We've had her I think 10(?) yrs, so that makes her about 15.
Diamond C is correct about needing less protein. Our two geldings lived on our big upper pasture without needing extra except in winter when things got snowed over......... Ella has been moved around from the upper pasture to our barn field to babysit foals - which means she got grain than and got FAT. So, we'd have to move her back onto the upper field. And OMG, would she COMPLAIN!

They were put on the same worming and hoof trim schedule as everyone.