Before doing anything else you might want to contact your state Dept of Ag to find out what kind of licensing/paper work/regulations you'd need to comply with.

From what I've heard, commercial feed mills are getting all kinds of regulations thrown at them and its only a matter of time before it starts hitting the farm level feed mills.

As far as being a waste of time it all depends on how much demand there is for what you want to sell.     Here I think it'd be a hard to make it go without getting hooked up with a well know feed brand.