If you are raising Pacific white shrimp, you have probably spent more time thinking about protein sources than about vitamins. That makes sense. Protein is the big line item. But when you swap out fish meal for soybean meal, the math on everything else changes too. Including vitamins you thought you had figured out. A research team at Jeju National University recently took a hard look at one vitamin in particular: pyridoxine, better known as vitamin B6. They asked a question a lot of shrimp nutritionists have been wondering about. When you move to a soybean-based diet, does the optimal B6 level stay the same? The answer, it turns out,…