Nutritional benefits of specialty corn grain hybrids in dairy diets.

Corn grain is a primary energy supplement in dairy diets and can contribute up to 30, 60, and 98% of the diet's protein, net energy, and starch, respectively. Specialty corn hybrids are one result of efforts to select corn based on nutrient content. Many of these hybrids, which include high lysine, high oil, waxy, white, and sugary, among others, have been the subject of renewed interest because of improvements in agronomic performance, commitments by marketers to preserve the identity of specialty grain, and improvements in our understanding of digestion and nutrient requirements. Nutrients targeted in corn for dairy cattle include protein content, amino acid quality (especially lysine and methionine that escape ruminal fermentation), starch (including form, texture, and digestibility), lipid content, fatty acid composition, and mineral composition and availability. Concentrations of protein and oil are highest in the germ, and both are negatively correlated with starch concentration. Efforts to improve lysine content are hampered by its negative correlation with total protein. Lactation studies to date have shown variable production responses to specialty corns; their value may be limited to replacing more expensive ingredients in dairy diets. Increasing the protein content of corn would have the most economic value in diets for cows producing less than 9500 kg per lactation. High lysine corn is currently of limited value; increases in ruminally undegraded lysine would increase its value in diets for cows producing more than 9500 kg per lactation. At current fat ingredient prices, high oil corn has limited economic value except in diets for very high production.