Is there anyway you can keep the block away from the goats? Like I’ve seen in cow/goat/sheep herds that they build this type of crate feeder for the little ones so that the adults can’t get to the feed and eat it. Like you could do that and make it only accessible to the donkey.
An idea I just had would be to build a little fence around the block (and use wire with small enough squares that the goats couldn’t lick/bite it) and then the donkey can just reach in and lick it (???)
Or, if you have a run in shelter, you could put the block up at the donkeys height (with a rope of some sort or on a little shelf that is sturdy) and then the donkey could like reach his head up and lick it but the goats do not get to it? I am not sure if your goats will climb to it or not, but it might work. Hope this helped a bit
~If you come at it having only 15 minuets it will take all day... If you come at it having all day it will take you 15 minuets~