Vegans and vegetarians can move along and enjoy their day. You're cool already, and off the hook.

Cows are ruminants. That's a group of animals that are specially adapted to eat nutritionally-useless grasses. That's their whole deal. If you're living in a pastoral or premodern farming society then that's great because you can't eat grass and you can eat cows, so it's free food. But instead you live in a society (insert meme) where we grow food specifically for cows then ship it to cows. Again, the animal that's specialized in eating things that have no nutritional value, so we're going out of our way to grow plants with no nutritional value, and then ship enough of it around to feed an animal anyway.

What does that mean? It means by whatever metric you choose, cow meat is worse than half as efficient as other common sources of animal protein.

Feed conversion ratios. Enough feed to make a pound of beef is enough to make 2.5 pounds of pork or 5 pounds of chicken.

CO2 per calorie. 1000 calories of beef costs 13.8 kg of CO2. 1000 calories of pork costs 4.45kg CO2. 1000 calories of chicken costs 3.37kg CO2. Also note lamb topping the charts, which will be a running theme. (Also an extra reason not to use broccoli as your primary calorie source, if eating 13 pounds of broccoli a day wasn't a good enough reason on its own.)

Land use per year per calorie. How much land did that 1000 calories take? You'll need 119 square meters for beef, 7.26 square meters for pork, or 6.61 square meters for chicken. Note lamb topping the chart again. (Also apparently prawns can be farmed super dense, that's something interesting that I didn't know.)

Why do sheep show up so high on some of these charts? Because they're also ruminants. Don't eat sheep either.