Maize is a Critically Important Source of Food, Feed, Energy and Forage in the USA

Maize production in the U.S. was about 316 million metric tons in 2010. That amount is expected to increase in the future due to greater yields/hectare and more hectares planted. From 1950 until 2006 the supply of maize grain was much greater than demand. Government programs supplemented farmers, enabling them to produce abundant amounts of maize grain at low prices. The low prices of maize grain encouraged feeding large amounts to livestock and poultry. As late as 2000,60% of maize grain produced was fed to livestock and poultry. The development of the fuel ethanol industry has changed both the price of maize grain and the usage by livestock and poultry. In 2010 only 42.9% of U.S. maize grain was fed to livestock and poultry while 41.8% was used for fuel ethanol production, and 11.2% for food. There are two byproducts from fuel ethanol production that replace some of the maize grain, especially in cattle production-distillers grains and maize gluten feed. Both of these byproducts are very well utilized by cattle. Depending upon plant production logistics, distillers grains has 110-140% the feeding value of the maize grain replaced and maize gluten feed has 100-110% the feeding value of maize grain. Values are less for lactating dairy cows but both byproducts serve as excellent protein sources. Byproducts replace 35-45% of the maize grain used to produce fuel ethanol. Essentially all of the cattle in the U.S. are "finished" on diets containing 80-85% concentrates. In the past the concentrates were comprised primarily of maize grain but now are a mixture of maize and byproducts. In the US the forage part of the corn plant is utilized in three ways. Some is harvested as whole plant maize silage. The silage is used as both an energy source and a roughage source in feedlot diets. Maize silage is also used to "background" cattle. This term is used to describe a growing phase based on forages prior to cattle being placed on "finishing" diets. The second use of maize forage (referred to as residue) is residue harvest after grain harvest and fed as a roughage source in finishing diets or mixed with wet byproducts and fed as an energy source to "background" cattle or beef cows. The other use of the maize "residue" is through grazing after grain harvest. Beef cows or backgrounding calves are placed on the maize fields after grain harvest where they select the higher quality forage components and any residual grain left in the field after harvest. Residual grain in residue is of high quality and selected first by the cattle. The husk is palatable and highly digested while the leaf is palatable but not as digestible. Quality of the diet declines with time of grazing because the higher quality parts are selected first. Generally, about 15% of the residue is consumed leaving 85% for erosion control and soil organic matter. Under this system beef cows need little supplementation while growing calves need supplementation of both protein and energy to yield economical growth. (C) 2012 Elsevier B.V. All rights reserved.