air potato vine safe for cattle?

Hi,
my mom is wanting to move her air potato vine to a fence that the cattle could possibly have access to & I have not had any luck finding out for her if these are hazardous to cattle. I did see a few sites that say that the raw yams can give humans a stomach ache, but nothing about cattle. If anyone has grown this & had cattle munch on it, PLEASE let me know the outcome.
Thanks

Hi PudgyMudpies,

I noticed your question was languishing, so I thought I should do a little reasearch.

This site has the most info I've found about Dioscorea Yams:

http://www.innvista.com/health/foods/vegetables/yams.htm

This page had some info about using african Dioscorea yams for cattle food:

http://www.fao.org/ag/aga/agap/frg/afris/Data/530.HTM

However, some african species of Dioscorea yams are definitely poisonous:

From this page http://www.manafoods.com/clark.htm

The tuber of Dioscorea bulbifera is also used by the natives of the British Cameroons in times of scarcity, but it is very bitter and requires repeated washings before it is eatable. The village pigs root it out and eat it if allowed to run free in the bush. The result is often fatal.