Beef CO2 emissions is more than cows breathing. Theres a lot of fuel burned when moving them around, making feed for them etc. I can't quite remember, but for every 100 calories of food eaten by cows, you end up with 3 calories worth of beef.
So right there off the bat, beef CO2 / calorie is 30x higher than the plants they eat (or whatever the multiplier was).
I grew up ranching and have read the research on this. They don't graze the same, they don't migrate the same, they don't eat the same plants, they don't have the same predators, etc. infact, we massacred to near extinction several keystone species to make way for cattle.
We also killed all the bison to cause famine in native American populations.
The real facts are:
1) beef is optional. Great during food scarcity, not necessary when food is abundant.
2) beef is extremely inefficient to produce. We're talking 20x+(likely much higher) than plant based proteins.
3) beef is horrendous for the environment.
4) over consumption of beef is the cause of a ton of public health issues.
5) animal cruelty
6) industrial ranching creates diseases or facilitates their spread.
Animals rights activists often hide this type of information to tie themselves to climate activism.