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Determining amino acid digestibility of soybean meal from different Midwest soybean varieties and growth performance when fed to broilers

Dunmire, K., M. Braun, C. Evans, C. Stark and C. Paulk

Abstract Body: Two studies were conducted to determine apparent ileal digestibility (AID) of amino acids (AA) and growth performance of broilers fed soybean meal (SBM) from different soybean varieties. Both studies used 1 of 4 soybean sources varying in quality defined by analyzed crude protein (CP) content. Two sources consisted of soybeans from similar regions processed conventionally or experimentally. Other sources included a low quality and high-quality soybean, experimentally solvent extracted at Texas A&M University. Therefore, dietary treatments consisted of a conventionally processed SBM (CSBM; 47% CP) or experimentally processed SBM 42SBM (42% CP), 49SBM (49% CP), or 52SBM (52% CP). In Exp. 1, 240 one-day old Cobb500 male broilers were placed in battery cages with 6 broilers per cage and 10 replicates per treatment. A common corn-SBM crumble starter diet was fed from d 0 to 10 with experimental diets fed from d 10 to 18 with SBM as the only source of AA. Dietary treatments were dextrose and SBM-based and consisted of 1 of 4 SBM sources included in diets formulated to 20% CP. On d 18, broilers were euthanized by CO2 inhalation and ileal samples were collected to determine AID of AA. In Exp. 2, 360 one-day old Cobb500 male broilers were placed in battery cages with 6 broilers per cage and 15 replicates per treatment. Dietary treatments consisted of the same SBM used in Exp. 1 and were formulated to 90% digestible Lys, balanced using digestible AA values determined in Exp. 1. All data were analyzed using the GLIMMIX procedure in SAS 9.4, with cage as the experimental unit, cage location as the blocking factor and adjusted using Tukey-Kramer multiple comparisons. In Exp. 1, increasing the CP content of experimentally processed SBM from 42SBM, 49SBM, to 52SBM increased (P < 0.05) AID of total AA (80.3, 84.9, 87.3%, respectively; CSBM 87.6%), Arg, His, Lys, and Thr with no evidence for differences between AID of CSBM and 52SBM. Broilers fed CSBM, 49SBM, and 52SBM had increased (P < 0.001) Ile, Met, Phe, and Trp compared to 42SBM. The AID of Leu and Val increased (P < 0.001) with increasing CP with CSBM intermediate to 49SBM and 52SBM. In Exp 2., from d 0 to 18, ADG and d 18 BW increased (P < 0.001) in broilers fed CSBM (37.7; 688 g) compared to 42SBM (31.9; 635.7 g), 49SBM (32.6; 640.0 g), and 52SBM (31.1; 635.0 g). Broilers fed the CSBM (45.6 g) had increased (P < 0.001) ADFI compared to 42SBM (40.8 g) and 52SBM (40.0 g) with 49SBM (42.2 g) intermediate.

In conclusion, SBM from high CP soybeans (52SBM) had increased amino acid digestibility compared to SBM from 42SBM and 49SBM with no differences between 52SBM and CSBM. However, broilers fed CSBM had improved d18 BW, ADG, and ADFI.