So if I were to raise one cow in my own pasture, and fed it only grass, my meat-related carbon footprint would be very small compared to that from buying the equivalent about of feedlot beef from a supermarket. It wouldn't be as low as if I just grew tomatoes and vegetables, but looking at it from a calorie standpoint, it's a pretty good investment:
Say a standard cow contains about 500,000 calories. *More in my situation considering I would eat (or feed to my dog) the parts of the cow that most people don't eat (heart, liver, intestine etc.)* That's 1370 calories per day for a year in ONLY meat (and I would never eat red meat -and meat in general- every day). Say the cow feeds three people (not three of me, just three people). That's 440 calories from an animal per day. Totally reasonable, considering where the meat comes from, and how it's raised.
Say I raise two cows. The marginal cost of raising a second is much less than that of initially buying a first. In addition, besides vet bills, the opportunity cost of time, and the energy I would have to use to freeze the meat or turn it into jerky, this would be a money-saving operation.
So, which is more economical:
a. growing your own vegetables (that you have to freeze or preserve for the winter as well)
b. growing your own animal?
Being a vegetarian is great and all, but if you're doing it for environmental reasons, how valid is it? Extremely valid if you don't have the means to hunt animals or raise them for food, but less valid if all you say is "Oh me oh my! The cattle industry produces so much greenhouse gas!" (Solution: don't buy unsustainable meat).
Know what you eat, and where it comes from.
Eat food, not too much, mostly plants.
Know where your meat comes from, if you eat meat.
Make reasonable decisions and weigh out all of your options in regard to your diet.