A Nobel Prize-winning chemist fed cows no protein at all for years, and they gave milk, and the milk was full of protein. Artturi Virtanen won his Nobel for chemistry in 1945. In the 1960s he took dairy cows off every protein in their diet and fed them urea and ammonium salts, which are nitrogen and nothing else, with cellulose and starch for energy. The cows made milk. Full milk, with every essential amino acid in it, for years, through several lactations. The microbes in the rumen took the nitrogen and built the protein from scratch, and the cow digested the microbes. They built every B vitamin as well, including B12, which no plant and no animal can make and which comes, in the end, from a microbe or nowhere. A cow is the only farm animal that manufactures protein. A pig and a chicken can only move protein from one place to another, and the place is usually a soy field. Feed a pig a kilo of soy protein and you get less than a kilo of pork. Feed a cow grass with no protein worth the name and you get a kilo of beef and milk anyway. Grazing cattle produce more protein a human can eat than they consume. A cow is a protein factory with a grass intake and a chemist-proof design, and she can run it on nitrogen and sunlight. Every plant-based plan to replace her begins with growing the protein first.