Different cattle feeding production systems have separate advantages and disadvantages. Most cows have a diet that is composed of at least some forage (grass, legumes, or silage). In fact most beef cattle are raised on pasture from birth in the spring until fall (7 to 9 months). Then for pasture-fed animals, grass is the forage that composes all or at least the great majority of their diet. Cattle fattened in feedlots are fed small amounts of hay or straw supplemented with grain, soy and other ingredients in order to increase the energy density of the diet. The debate is whether cattle should be raised on diets primarily composed of pasture (grass) or a concentrated diet of grain, soy and other supplements. The issue is often complicated by the political interests and confusion between labels such as "free range", "organic", or "natural". Cattle raised on a primarily forage diet are termed grass-fed or pasture-raised; for example meat or milk may be called grass-fed beef or pasture-raised dairy. However, the term "pasture-raised" can lead to confusion with the term "free range", which does not describe exactly what the animals eat.In the United States, cattle in concentrated animal feeding operations (CAFOs) are typically fed corn, soy and other types of feed that can include "by-product feedstuff" such as stale pastry, candy, and recycled municipal garbage. As a high-starch, high-energy food, corn decreases the time to fatten cattle and increases yield from dairy cattle. These cattle are called corn-fed or grain-fed. In the United States, most grass fed cattle are raised for beef production. Dairy cattle are usually supplemented with grain to increase the efficiency of production and reduce the area needed to support the energy requirements of the herd. A growing number of health and environmental proponents in the United States such as the Union of Concerned Scientists advocate raising cattle on pasture and other forage. Some claim that the adoption of a grass-fed beef production system would dramatically increase the amount of land needed to raise beef. While grass-fed beef would take more initial land for foraging, when corn fed beef’s total is squared with the land needed for corn production to feed grain-fed beef, the total would likely be more equitable.