I have a 4 year old Morgan who I am starting in harness this summer. I am a novice and will welcome any help.
Something, really fun, that I did this last winter to get him used to pulling weight was ski-joring. I towed my 11 year old daughter around on skis. I also made up a quick release belt for myself and long lined him while he pulled me......we had a blast and so did he. He accepted the task very well.
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