Supplementing nutrients to offset deficiencies or to meet production demands is more often practiced during periods of summer dormancy or during the fall and winter months. Substitution can be practiced when forage resources are in short supply (Caton and Dhuyvetter, 1996). When forage intake is greater than 1.75% of bodyweight, supplements may decrease forage intake. When forage intake is less than 1.75% of bodyweight, supplements almost always increase forage intake.
Forage intake response is affected by the forage ratio of digestible organic matter to crude protein (DOM:CP). When DOM:CP ratio is less than 7, supplements decrease forage intake; when DOM:CP falls between 7 and 12, intake may both increase and decrease with supplements. When DOM:CP is greater than 12, all type of supplements increase forage intake.