Effects of Feed Intake and Physical Form on Energy Value of Corn in Timothy Hay Diets for Lactating Cows

Six lactating cows in two 3 3 Latin squares were fed diets containing 45% corn grain, 40% US #1 timothy hay, and 15% of a concentrate mixture composed of 86% soybean meal, 5% cane molasses, and 9% dicalcium phosphate. Three diets differed only in physical form of the corn grain that was whole, cracked, or ground through .64 cm screen. A third Latin square of three nonlactating cows at maintenance intake were given 55.5% corn, 40% timothy hay, and 5.5% concentrate mixture. For the diets of whole, cracked, and ground corn, the digestible energy (Mcal/kg dry matter) was 2.32, 2.46, and 2.66 for lactating cows and 2.55, 2.64, and 2.80 for nonlactating cows. The metabolizable energy (Mcal/kg dry matter) was 1.93, 2.11, and 2.29 for lactating cows and 2.13, 2.24, and 2.40 for nonlactating cows. Digestible energy and metabolizable energy concentrations differed among diets for the lactating cows and also differed between lactating and nonlactating cows.