Livestock produces as much green house gas emission than aviation. It sounds like a good argument for vegetarians, why one should reduce the consumption of animal products.
The situation in a developing country, in which population crucially lacks in proteins, is different. Reducing livestock, that is the major source of protein, does not seem a smart option despite of the fact that it produce most of livestock related greenhouse emission.
In fact, livestock is generally not well managed, free grazing leads to overgrazing and examples like area exclosure (see post http://catherinepfeifer.blogspot.com/2011/11/bahir-dar-reporting-series-do-you-think.html ) can significantly improve productivity of livestock without increasing green grass emissions. For developing countries the solution lies in improving livestock and its benefit rather than reducing it. This implies improving breeds, improving fodder availability and quality (more proteins) in order to increase livestock productivity.
A very good overview over livestock and green gas emission both in developed and developing countries can be found in the Wageningen World magazine :