This is the comment made some days ago in the news about meat and CO2 emissions.
This idea that animals just eat the produce of intensive farming (or that grazing pastures are planted by men specifically for that purpose) is wrong in many parts of the world.
We have the obvious example of Argentina, where free grazing cattle uses the naturally available grass to get fed.
In the case of Southern Europe, there are also goats that have been used to clean the forests for a long time in order to prevent fires, and that provides for most or even all of their feeding requirements (besides fulfilling the important role of fire prevention).
The idea going around how animals are so inefficient per Kg of food/Kg CO2, fails to take into account (basically all the time) that part of those animals, only consume naturally occurring flora that is in no way planted by men.
P.S.: As an interesting related side note, there are a lot of cooking recipes for old goat in Portugal (the meat needs to be cooked differently).