Pre columbian livestock numbers have little bearing on
greenhouse gasses today.
Unfortunately grassfed livestock produce more methane than feedlot do.
I don't have the data in front of me but it's unfortunately true.
Methane is 20 times more potent as a
greenhouse gas than carbon is, so I'm not sure of the logic behind this one
You might want to check this one out though.
http://www.agrometeorology.org/news/whats-new/japanese-researchers-discover-method-to-stop-cattle-from-emitting-methane Personally I've been talking with Professor Takahashi at the Obihiro University of Agriculture here in Japan, and I'm currently using Yucca Shidigera extract at 0.1% of
feed until a usable Cysteine based product comes into production.