Evergreen leaves are they harmful?

In my pasture, there are several trees, Cedar Trees, and Douglas Fir trees. My alpacas constantly nibble on the branches or more specifically the needles. I try to discourage it but they also manage to get into them. I have looked online to see if evergreens are harmful to Alpacas and can not find any specific info about it. For sheep, it is not a problem. I have not noticed any problem with their poop nor with their general health and they have been eating these leaves for quite some time. Does anyone have any additional knowledge about this. Is it enough of a problem for me to be concerned?

 

I find references online to Llamas eating evergreens with no problems. I know goats can eat them, love them actually. I would bet that the alpacas are fine with them but if you ever breed them they 'might' cause abortions if they eat them while pregnant. I have to watch that with my goats.

 

Make sure the cedars are in fact cedar and not yew.
yew=bad.