Are mulberry leaves poisonous?

I posted in a previous blog that mulberry leaves are poisonous, but when challenged by one of my readers I decided I needed to research this subject.  I'd always been told that dried mulberry leaves were poisonous.  Although I've never had any problems with my livestock, they refuse to eat dry mulberry leaves so I had no proof either way.
http://www.fao.org/ag/AGA/AGAP/FRG/Mulberry/Papers/HTML/Mulbwar2.htm

Mulberry: an exceptional forage available almost worldwide! states that the leaf mineral content is high and no anti-nutritional factors or toxic compounds have been identified.

Mulberry leaves as sheep feed supplement discusses a study that was done to figure out the nutritional content of mulberry leaves.  In this study, they dried the mulberry leaves and then fed them to sheep.

So it looks like mulberry leaves are perfectly safe even when dry!  On top of all this, the leaves are full of protein and rich in nitrogen, sulphur and minerals.  Mulberry leaves caused increased body weight gains in growing lambs and goats, and also included milk production in goats.  Some authors even say that mulberry leaves are as good as alfalfa and other high quality forage.  Therefore, my conclusion is mulberry leaves are not poisonous.  Instead, they make excellent feed fresh or dry!!