A process for obtaining high ethanol yield from the fermentation of an energy crop and for producing a nutritionally enhanced feed co-product is provided. In particular, the process includes converting non-fermentable polysaccharides in an energy crop into fermentable sugar. The fermentable sugars may be fermented into ethanol thereby enhancing the ethanol yield. In addition, separation of ethanol from the fermentation product yields a whole stillage product having enhanced protein content and reduced fiber content. The process requires little or no modification to the configuration of existing commercial ethanol facilities.