Digestibility of energy and nutrients in soybean expellers produced from conventional or high-oil varieties of soybeans and fed to growing pigs

The objective was to test the hypothesis that standardized ileal digestibility (SID) of amino acids (AA), metabolizable energy (ME), and standardized total tract digestibility (STTD) of P in soybean expellers produced from a new variety of high-oil soybeans (SBE-HO) are not different when compared with expellers produced from conventional soybeans (SBE-CV). In experiment 1, 9 barrows (30.0 ± 1.5 kg) that had a T-cannula installed in the distal ileum were allotted to a triplicated 3 × 3 Latin Square design with 3 diets and 3 periods in each square. An N-free diet and 2 diets containing SBE-CV or SBE-HO were used. Pigs were housed individually in fully slatted pens and ileal digesta were collected on days 6 and 7 of each period. Ileal digesta and diets were analyzed for AA, and SID of AA was calculated. Results indicated that the SID of Arg, Ile, and Lys was not different between the 2 sources of soybean expellers, but the SID of other indispensable AA was greater (P < 0.05) in SBE-CV compared with SBE-HO. However, because of greater AA concentration, SBE-HO had greater concentrations of digestible Arg, Lys, Met, and Trp compared with SBE-CV. In experiment 2, 30 pigs (18.3 ± 1.3 kg) were randomly allotted to 3 diets containing corn, corn and SBE-CV, or corn and SBE-HO as energy sources. Pigs were housed in metabolism crates and feces and urine were separately collected for 4 d after 5 d of adaptation. Feces, urine, and diets were analyzed for gross energy and ME was calculated. Results indicated that ME in SBE-HO was not different from ME in SBE-CV. In experiment 3, 48 barrows (12.0 ± 1.6 kg) were allotted to 6 diets. The SBE-CV and SBE-HO were included in diets with 3 levels of microbial phytase (i.e., 0, 500, or 1,000 units/kg). Pigs were housed in metabolism crates and feces were collected quantitatively for 4 d after 5 d of adaptation. Feces and diets were analyzed for P and the STTD of P was calculated. Results indicated that the inclusion of phytase in the diets linearly (P < 0.001) increased the STTD of P regardless of the source of soybean expellers, but STTD of P was not different between SBE-HO and SBE-CV. It is concluded that if SBE-HO is included in diets for pigs instead of SBE-CV, slightly less soybean expellers are needed to meet AA requirements due to greater concentration of limiting AA, but ME and STTD of P will not be changed.