A broad term that can have a number of different applications: 1) A specific ration designed to be fed to grazing animals or animals on hay. This will include the protein, energy (grain), supplemented vitamins, minerals, amino acids to balance with forage portion of the diet. 2) A specific ration as above to be added to the grain and forage on farm to make up a complete feed. 3) Any nutrient fed in addition to the basic ration is also a supplement to the overall rations and will contribute to the overall total daily nutrient intake.