Amino acid digestibility and net energy concentration in soybean meal for broiler chickens

Abstract

The objective of this study was to determine coefficient of standardized ileal digestibility (CSID) of amino acids and net energy (NE) concentration of soybean meal (SBM) in broiler chickens. Six SBM originating from different regions in the United States were used in the current study. In experiment (Exp.) 1, a total of 576 birds on d 16 post hatching were allotted to 7 diets consisting of 6 diets containing 440 g/kg of each SBM as the sole source of nitrogen and a nitrogen-free diet. Birds were fed from d 16 to 21 and euthanized for the ileal digesta collection on d 21 post hatching. In Exp. 2, birds were fasted for 12 h on d 17 post hatching. On d 18, birds were divided into an initial (8 birds) and final group (64 birds), and the initial group was euthanized and immediately frozen. The remaining 64 birds were assigned to a basal diet or test diet replacing the basal diet with 200 g/kg of SBM. Experiment 2 lasted 7 d and excreta collection was conducted during the last 3 d. On d 25, birds were euthanized after a 12-h fast, individually weighed, and immediately frozen. The whole frozen intact bird carcass was ground and analyzed for gross energy. Energy retention was estimated as a difference in total body energy between the initial and final groups. In both experiments, the experimental design was a randomized complete block design with body weight as a blocking factor. In Exp. 1, the CSID of several indispensable amino acids in SBM1 was greater (P < 0.05) compared with SBM2, SBM3, and SBM6. In Exp. 2, energy retention was greater (P < 0.05) in the basal diet group, whereas NE for maintenance was lower compared with the test diet group (P < 0.05) resulting in a tendency for greater NE intake in the basal diet group (P = 0.084). Values for metabolizable energy (ME), nitrogen-corrected ME, and apparent total tract utilization of gross energy and nitrogen were greater (P < 0.05) in the basal diet group, however, a statistical difference in NE and dietary NE to ME ratio between the basal and test diets was not observed. In conclusion, different values for CSID of amino acids should be applied when formulating broiler diets containing SBM; furthermore, ME, NE, and NE to ME ratio in SBM were 12.61 MJ/kg dry matter, 8.58 MJ/kg dry matter, and 0.682, respectively.