I did a little research on the ingredients and compared to a bottle of ferretone and this is what I found.....

I did an analysis of the ferretone recipe in an effort to come up with the proper of vitamins to add to the recipe, but I discovered something else too.  I looked up the nutrient contents of all the oils to see what vitamins are already in them.  I discovered that soybean oil & wheat germ oil only have a small amount of Vitamin E (nothing else) and cod liver oil has great amounts of Vitamin E and D3.  Flax seed has so many other nutrients and vitamins (Calcium, Iron, Magnesium, Phosphorus, Zinc, Copper, Manganese, Selenium, Vitamin C, Thiamin, Roboflavin, Niacin & Folic Acid), that I would substitute that for the soybean & wheat germ.  To get proportions close to the commercial Ferretone, the ratio would be 9 ounces flax seed to 1 ounce cod liver.  This will give you 60 teaspoons per batch, which considering the spoilage rate, is probably how much you would want on hand.  Most cod liver oil comes with Vitamin A already added to it, which means you would only have to add 24 mg of Vitamin B6 to the mix.  One tablespoon of lecithin should also get you close to the Linoleic Acid, Linolenic Acid, Choline and Inositol.