We have three donkeys that have all been used for halter breaking... two mammoths and one standard. All are Jennys. They all work good but the smaller standard is by far the best one. I have no idea how she does it, but she can take all the fight out of any animal after two hours of being tied up... and she hardly does anything. She usually just stands in one place and if she decides she wants to go anywhere, she simply starts walking in circles, each time around getting a little closer to the hay or water or wherever she wants to go. Two years ago I had a 1300 lb bred heifer who had never had a rope on her before. I haltered her and tied her up in the barn. She was flipping herself over and smashing her head and had blood running out of her nose. I was afraid to leave her tied up as I thought she was going to hang herself or hurt herself badly. I was wanting to go cut some hay so I knew I either had to turn her lose or tie her to Elizabeth and turn her out in a pen. I decided to try the donkey and tied her to her and went to the hay field. Two hours later I came in for lunch. They were standing exactly where I had left them. I was going to try to lead Elizabeth into the barn so that I could untie the heifer, and she refused to move, so I decided to untie the heifer and see if she was going to take off on me. I untied her and lead her into the barn... she never even stopped once and hardly tightened the rope. She was good from that time on, and after combing her a couple times, you could do anything with her.
In the late summer, the donkey is invaluable. I usually have 15 - 20 head to get halter broke for sales and shows. Elizabeth allows me to do some other jobs while she is on halter breaking detail. The other two Mammoths are also OK but they are a little rougher on the calves.