Nothing. Literally there is no nutrients that can be found in meat which are not in plant based foods. Here is a video from kurgesagt:Why Meat is the Best Worst Thing in the World Meat takes more than 12 hours to digest in gut compared to any other plant based foods it's pretty high, on top of that this much of consumption(literally in millions of tons) of meat is never a thing for a humans of the past, but unfortunately modern human started consuming too much of it so much so that in matter of decades our planet could turn into a brown looking planet from something that looked green due to to much of production of meat.