> You need heme iron.
You don't have to eat the cow, but it would be a waste to give it to the dogs when it dies. And you would thrive more if you did eat it.
I have always hated the taste of meat. My pet theory is that some bodies simply can't handle it.
If you live on only animal products you are likely to get diseases like scurvy, or like the Inuit have a rampant rate of atherosclerosis.
B12 is produced by bacteria in the dust, meat in modern factory farms only has it because it gets injected in the animals.
Living in nature drinking from spring water and not washing everything so throughly we would get all the B12 we need. Instead of injecting the supplement in the cow and eating it, just take it straight.
> There are plenty of nutrients found in meat and not found in plants
Literally all nutrients in meat come from plants, or can be made by our body based on plants, there are no magical nutrients in meat it's myth.
> They are also in a less bioavailable form,
Certain nutrients like iron are excessively concentrated in meat, and eating it every day 3 times a day is toxic, so having less of it per volume is a good thing not a bad thing.
All the vitamins that you need are available in plants, A, K2, you name it. There is no magical nutrient missing they all come from plants.
As you mentioned, your body also produces vitamin D, you can go outside which is healthy anyway and that's it. Your body produces Vitamin D just like the animals.
Our body can either consume directly or produce based on plants anything that it needs in sufficient amount.
There is nothing magical about meat, its completely optional for a healthy human diet in all stages of life - https://www.ncbi.nlm.nih.gov/pubmed/19562864
B12 only comes with veggies if you don't clean them, i.e., if you risk food borne diseases. Otherwise you need supplements.
Meat is optional if you eat enough unwashed veggies. Veggies are optional if you eat enough meat. Societies have survived for centuries with both diets, but the thriving societies were all omnivorous.
One can live on pure animal product alone and not need any supplements, yet one can't do the reverse. If you eat only plant food you must consume supplements.
There are plenty of nutrients found in meat and not found in plants.
B12 is the big supplement not found in plant foods, and the supplement was invented in 60s. So no true vegans could exist until then. Vegetarians existed, but they ate some animal products.
Plants also have no Vitamin A, only carotenoids which is difficult for our bodies to convert to Vitamin A.
The vitamin D found in plants is inferior to the vitamin D in meat. Most of us don't get enough sun for adequate vitamin D.
Vitamin K2 is also severely lacking in plants.
Heme iron is also only found in animal products. You need heme iron. For most people iron overload is not a worry, you need some genetic disposition to absorb extra iron.
We can't eat grass like a cow, but we can eat that cow.
You've made some claims without an examples. Can you give me an example of nutrients that are found in plants and not in animals?
Also the definition of an "essential nutrient" is a nutrient that we can't synthesise ourselves in our bodies. So no we can't make any essential nutrient because that's the very definition of the phrase.
https://www.sciencedaily.com/terms/essential_nutrient.htm