Evaluation of heat-processed sorghum, high-oleic and low-trypsin inhibitor soybean cultivars as alternatives for corn and conventional soybeans for broilers
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Four 21-d experiments were conducted to compare soybean meal (SBM) from high oleic to parent soybean cultivars on growth performance, energy and ileal AA (IAA). Soybean meal was prepared by laboratory-scale mechanical extraction. Two replicate chick assays (Exp. 1 and 2) with similar treatments were conducted to evaluate the growth efficiency. In Exp. 1 and 2, 50 d-old male broilers (Ross 308) were randomly placed in battery cages and allocated to 2 dietary treatments with 5 replicates and 5 birds per replicate. The SBM sources consisted of cold-pressed conventional SBM (CON) and cold-pressed high oleic SBM (HO). All SBM sources were heated in a forced-air oven at 120 degrees C for 20 min. Diets were formulated to meet or exceed NRC (1994) and Aviagen nutrient requirements for Ross 308 in Exp. 1 and 2, respectively. Broilers were weighed and feed disappearance measured on d 7, 14, and 21 in Exp. 1, and on d 10 and 21 on Exp. 2. Two assays (Exp. 3 and 4) were conducted to determine IAA digestibility and apparent metabolizable energy (AME) in Exp. 3 or ileal digestible 24 energy (IDE) in Exp. 4. In Exp. 3 and 4, 100 d-old broilers randomly allotted to 2 dietary treatments with 10 replicates and 5 birds per replicate. Chicks were fed a corn-SBM based diet for 17 d, and a diet was developed by substituting the soybean cultivars in a corn starch-dextrose basal diet and fed from d 18 to 21. A nitrogen-free diet was fed to determine ileal endogenous AA losses. Titanium dioxide (0.5 percent) was included in all diets as a digesta flow marker. Excreta and ileal samples were collected on d 21. Statistical analyses were performed as a completely randomized design using PROC GLM of SAS with significance level set at P less than or equal to 0.05. In Exp. 1, chicks fed diets containing HO had decreased ADG (P less than 0.05; 25.3 vs. 29.4 g) and increased feed:gain ratio (P less than 0.05) from d 0 to 14 (1.71 vs. 1.56) and d 0 to 21 (1.54 vs. 1.47), compared with chicks fed CON diet. In Exp. 2, chicks fed HO had lower BW at d 10 (P = 0.028; 143 vs. 153 g), lower ADG from d 0 to 10 (P = 0.030; 10.90 vs. 11.90 g), and greater feed:gain ratio from d 0 to 10 (P = 0.043; 1.55 vs. 1.45) compared with chicks fed CON diet. In Exp. 3, AA digestibility did not differ among all essential AA. There were no differences in AME (kcal per kg) from SBM between CON and HO, with values of 2,921 and 2,901 (P = 0.73), respectively. In Exp. 4, the digestibility of glutamic acid (P = 0.026; 94.4 vs. 95.2 percent) and arginine (P = 0.008; 94.4 vs 95.4 percent) from HO were lower than CON; however, the IDE of CON and HO were similar (3,419 and 3,343 kcal/kg; P = 0.08), respectively. In conclusion, although there were no differences in nutrient digestibility, in conditions of this study, broilers fed HO had impaired growth performance, mainly from 1 to 14 d of age.