Hi Pam,
Have you done any blood testing (insulin/glucose) on your donkey friend?  If he’s an intact male and not gelded, the likelihood of his being insulin resistant is slim, or it would be if he were an intact male horse.  Is he full grown at three?  You can tell I’m not the donkey expert here but IR tends to become evident after the horse reaches maturity.  While proper nutrition is important for every horse, mule and donkey, being IR makes it even more critical but, if his insulin levels are low, your concerns might be reduced.
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