Concentrations of the forage nutrients protein, carbohydrates, minerals, vitamins, and antiquality components such as tannin are genetically controlled and can be altered by selection. Digestibility, palatability, intake, and plant structure, which determine the percentage of nutrients in a forage that are available to the animal consuming it, are also genetically controlled. Generally, inheritance seems to be polygenic. Index terms: forage plants, livestock nutrition, plant genetics, plant nutrients.