A livestock feed supplement providing high by-pass protein, being substantially free of urea and molasses, and providing good palatability. The supplement is formulated using byproducts of grain alcohol fermentation, namely distillers dried grains obtained from the stillage of fermented, dry-milled whole grain, and condensed distillers solubles from such stillage. Standard amounts of other nutritional supplements, including vitamins and minerals, are added to the composition to form the block. The supplement may be compressed and cured into a substantially hard block for free-choice feeding, or packaged in its granular, somewhat moist form for subsequent mixing in livestock feed. The byproducts of the fermentation include natural flavors that provide good palatability without the addition of sweeteners such as molasses.