I don't feed fodder at the moment but I'm really looking forward to it. Rule of thumb is to feed 1%-3% of body weight (1-3 pounds per 100 pounds of bodyweight). How much depends on the situation of course - a young growing kid, pregnant or lactating doe, or just a buck or wether. If you are on facebook you might want to join the "Fodder" group - super helpful, friendly people who can answer almost any Fodder related questions.