Corn Genetics and Animal Feeding Value

Grain and forage from corn plants vary in composition and digestibility due to genetics and numerous environmental factors. For decades, corn hybrids have been selected based on agronomics (yield, disease and insect resistance). In addition, hybrids have been developed or selected for specific traits desired in specialty markets (food manufacturing properties: popcorn, white color, waxy, high amylose). More recently, hybrids have been screened for novel traits of either the grain (starch extractability, ethanol yield, digestibility by non-ruminants) or the forage (NDF content, NDF digestibility, lignin content). In the future, yield of biogas (methane) from different corn hybrids may become a selection criterion. Thanks to transgenics, hybrids with specific agronomic advantages (resistance to corn borers and corn rootworm; tolerance to herbicides) have been commercialized or are being developed (efficiency of nitrogen use; drought tolerance). Based on a comprehensive literature summary, no consistent differences in nutrient composition or in productivity of lactating or feedlot cattle or swine were detected between commercialized transgenic and near isogenic hybrids. With selection of hybrids for greater energy density (more lipid) or altered lipid composition, feeding value as well as certain attributes desired in animal products (altered fatty acid content; increased antioxidant concentrations; shelf life; taste) can be improved. Through altering grain density and metabolic pathways, genetic strains have been developed with increased concentrations or availability of specific nutrients or components (phosphorus; starch; protein or specific amino acids). Ideal traits for a hybrid differ among segments of the livestock or agricultural industry. Corn producers generally select hybrids based on grain yield and production cost; for livestock producers, the primary concern is feed efficiency or production per bushel or ton; for farmerfeeders, both grain yield and animal productivity must be combined in order to maximize beef or milk production per acre. To reap economic benefits from grain or silage with superior nutritional characteristics, linkage of producers directly or indirectly with livestock producers is necessary. Rapid and accurate analytical tools being developed are giving grain users the capacity to determine value more precisely. Empowering grain and silage traders and users with discriminatory power, such tools will permit livestock feeders to impose price premiums or discounts that reflect the true nutritive of the grain or silage.