The metabolizable energy and standardized ileal digestibility of amino acids in dry extruded-expelled soybean meal in comparison with solvent-extracted soybean meal fed to broiler chickens

The thermal treatment during extrusion can inactivate antinutritional factors in soybeans. Expelling extraction leaves behind soybean meal with higher contents of oil than solvent extraction does. The combination of these processing techniques results in dry extruded-expelled soybean meal (DESBM). It is expected that the feeding value of DESBM is high for broiler chickens, making it important to determine the nutritive values of DESBM to be used in broiler diets in comparison with solvent-extracted soybean meal (solvent SBM). An experiment was conducted to determine the standardized ileal digestibility (SID) of amino acids (AA) and the apparent metabolizable energy (AMEn) contents of DESBM and solvent SBM. Two hundred and forty broiler chicks were divided into 40 groups of 6 birds balanced for body weight and fed 5 experimental diets in a completely randomized design (8 groups/diet) from age 14 to 21 d. Two basal diets were cornstarch-DESBM-based and cornstarch-solvent-SBM-based diet. A portion of cornstarch and SBM in each basal diet were replaced by 30% of DESBM for cornstarch-solvent-SBM basal diet and 30% of solvent-SBM for cornstarch-DESBM basal diet. A cornstarch-casein based diet was also included to estimate basal endogenous AA losses for determining the SID of the AA. From d 19 to 21, excreta samples were collected for AMEn determination. On d 21, the birds were euthanized, and the contents of the ileums were obtained for determination of AA digestibility. The AMEn contents of SBM were determined by the substitution method, whereas the SID of the AA in SBM were directly determined from each basal diet. All data were analyzed using the mixed procedure of SAS. The apparent total tract retention of energy in the DESBM fed to broilers was lower (P = 0.03) than that in the solvent SBM. However, no difference in AMEn contents was observed between the DESBM (2,390 kcal/kg) and solvent SBM (2,314 kcal/kg). The SID of the AA in the DESBM and solvent SBM ranged between 79.6%–95.6% and 87.45%–94.2%, respectively. The SID of Ile, Leu, Met Ala, Asp, Gly, Ser, and Tyr in the solvent-SBM were greater (P < 0.10) than those in the DESBM. The higher dietary fiber content in DESBM than that in solvent SBM may lead to lower SID of AA and energy digestibility in broilers. 

Key words: broiler chickens, dry extruded-expelled soybean meal, energy content, standardized ileal digestibility.

Published in the proceedings of the Animal Nutrition Conference of Canada 2020. For information on the event, past and future editions, check out https://animalnutritionconference.ca/.