Trees... help!!

my mare tori has decided that all the young gum trees (about 5-7mtrs) taste great... and has gone ahead and is absolutely destroying all of them... my nanny and grandad (whose property it is) are concerned about all the trees dying and also we all were wondering (and i think) it might be a mineral deficiency?
what do you all think?
it's getting quite bad, i let her out of her yard to feed her thismorning and she ran and i mean "ran" straight to a tree and started to destroy it.
shes getting tonnes of feed and has just had her teeth done... so im a bit confused... i've never had a horse so bad with trees haha

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Try contacting Richard Marsden, he's the Kohnkes Own rep for WA and is very good with feed/nutrition issues. I would ask him and see if he thinks it is nutrition issue.

His email address is: richardpmarsden@bigpond.com

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I'm no horse expert. I have only had my first horse for a bit over a year. But could your problem be a vice of some sort? I noticed that my horse/s would occasionally nibble on a tree when they where bored, is your horse getting enough exercise for how much protein she is eating? Back to the vices thing, your horse may have a physcologial reason why she nibbles on trees. Or it is her way of crib biting? I have been told that pepper spray will stop horses from crib biting, but im not sure what it will do for the tree's. But try Richard Marsden first, he will have by far better information to help you.