Nutritional benefits of specialty grain hybrids in beef feedlot diets

The study of grain hybrids with faster or more extensive rates of ruminal s tarch fermentation has been a key research area. Because grain sorghum star ch is generally regarded as less accessible to enzymatic degradation than s tarch in other grains, it has received the greatest research emphasis. Howe ver, all grains have been evaluated to some extent. Grain sorghum hybrids a ppear to be more variable in digestibility, in vitro and in vivo, and in ra te of starch fermentation than are corn hybrids. The greater variation may be partially because grain sorghum hybrids are developed and evaluated unde r more stressful environmental conditions thigh temperature and limited wat er conditions) than are corn hybrids. In vitro and in vivo studies indicate that differences in grain hybrids exist, but these differences may not tot ally explain differences in cattle performance. The response to feeding hig h-lysine corn to cattle has been variable. Although high-lysine corn suppli es more lysine in the diet, lysine flow to the abomasum was not increased. Hybrids selected for increased lysine content have been shown to have faste r in vitro rates of starch digestion, suggesting that improvements in anima l performance may be related to the indirect selection for improved energy utilization. In one study in which high-oil corn was evaluated, feed conver sion was not improved compared with a control corn diet. At the present tim e additional studies in which other genetic modifications of grain hybrids are evaluated are in progress, but the results have not been published. (C) 1999 American Society of Animal Science and American Dairy Science Associa tion. All rights reserved.