Nitrogen-Corrected Apparent Metabolizable Energy Value of Crude Glycerol for Laying Hens
Dozier, W. A.
Weber, T. E.
Kidd, M. T.
An experiment was conducted with laying hens to determine the AMEn value of crude glycerol, a coproduct of biodiesel production. Crude glycerol (87% glycerol, 9% water, 0.03% methanol, 1.26% Na, and 3,625 kcal/kg of gross energy) was obtained from a commercial biodiesel production facility (Ag Processing Inc., Sergeant Bluff, IA). A total of forty-eight 40-wk-old laying hens (Hy-Line W-36) were placed in metabolic cages (2 hens/ cage) and given free access to the experimental diets. A corn and soybean meal-based basal diet (18% CP, 2,875 kcal/kg of AMEn, 4.51% Ca, 0.51% nonphytate P) was formulated with 15% glucose·H2O and 1% Celite. Four dietary treatments were created by substituting 0, 5, 10, or 15% crude glycerol for glucose·H2O (3,640 kcal/kg of AMEn). After 7 d of dietary adaptation, excreta were collected twice daily for 3 d, freeze-dried, and analyzed for contents of DM, Kjeldahl N, acid-insoluble ash, and gross energy. Egg production was recorded daily, and eggs were collected on d 7 and 8 of the experiment for calculation of egg mass (egg production × egg weight). Feed consumption was measured over the 10-d experimental period. Egg-production data were analyzed by ANOVA with 4 treatments and 6 replications in a completely randomized experimental design. The AMEn value of crude glycerol was estimated as the slope of the linear relationship between the inclusion rate of dietary crude glycerol and the glucose-corrected AMEn value of the experimental diets. No significant treatment effects (P > 0.1) were apparent for egg-production rate (93.0%), egg weight (56.1 g), egg mass (52.2 g/d), or feed consumption (104 g/d). Linear regression analysis (P < 0.001, r2 = 0.92, n = 24) revealed that the AMEn value of the crude glycerol used in this study was 3,805 ± 238 kcal/kg (mean ± SEM; as-is basis) for laying hens.