According to https://www.mdpi.com/2076-2615/2/2/127/htm conventional feedlot beef produces 501,593 kg of methane per 1 million kg of beef, mostly from both burps and composting manure. So that’s about .5 kg of methane per kg of beef.

1 lb of methane is 84 kg CO2e; that is to say over 100 years 1 kg of methane warms the planet the same as releasing 84kg of CO2. So every kg of beef produces 42kg of CO2e, regardless of any quibbling about the CO2e of agricultural waste fed to cows.

By contrast, googling quickly the quoted CO2e emissions per kg of chicken is 18.2. Which is, of course, subject to the same quibbling.