About half of the emissions from cattle are from methane; methane has about 80x the warming impact over 20 years that CO2 has.
Beyond that, cattle are slaughtered at 1 to 2 years old, while meat chickens are slaughtered at around 2 months. Cattle have worse feed conversion rates because they live longer.
as I said above, it’s almost impossible to actually quantify the effects of any agricultural activity due to the interdependencies and variances in the industry. show me the source for you “half of the emissions” claim, and I’ll show you a flawed methodology and a counterexample to the claim.
The half of emissions that are methane are the cow burps themselves, because their stomachs ferment grass and produce methane as a waste product.
Even if you want to quibble about the accounting of the other half, without cows grazing there would be way, way less methane produced.