t say much, except that you have to make sure you replace all the nutrients that most/
many of us get from meat.
One ounce of lean ground beef has the following nutrients: Protein, Niacin, Vitamin B6, Phosphorus, Zinc and Selenium, and a very good source of Vitamin B12. It's also a good source of iron. Chicken and fish have similar nutrients, often with less fat, or at least with the "good" fats.
I'm not real clear on the vegetarian "rules".