Abstract
The apparent metabolizable energy (AME), AME corrected to zero-nitrogen retention (AMEn), and net energy (NE) values of 2 corn samples both stored for 3 yr were determined in laying hens with reference diet substitution method. Reference diet was formulated according to standard layer requirement, and test diets contained 50% of corn samples and 50% of the reference diet. Fifty-four Hy-Line Brown hens at the age of 36 wk were used. The heat production and energy metabolism of birds were measured in open-circuit respiratory chambers with 6 replicates (3 birds per replicate) per diet in a randomized design. Birds were fed experimental diets for 7 D in the chamber as adaptation. During the following 3 D, feed intake, metabolizable energy value, nitrogen balance, energy balance, egg production, O(2) consumption, CO(2) production, and energy efficiency were determined. The AME values of corn 1 and corn 2 were 3,485 and 3,675 kcal/kg DM, respectively. The corresponding AMEn values were 3,452 and 3,596 kcal/kg DM, and the NE values were 2,575 and 2,693 kcal/kg DM, respectively. The NE:AME ratios of corn 1 and corn 2 were 74.4 and 73.3%, respectively. The NE:AMEn ratios of corn 1 and corn 2 were 75.0 and 74.9%, respectively. The AME, AMEn, and NE values of the 2 corn samples both stored for 3 yr were lower than the literature values for fresh corn.