Effects of an enzyme mixture supplementation on energy and nutrient digestibility in soybean expellers fed to growing pigs

Soybean expellers (SBE) are a product of soybean that is produced through extrusion followed by expelling and that is of great interest as a feed ingredient for swine due to its high fat and protein contents. An experiment was conducted to determine the apparent total tract digestibility (ATTD) of energy and nutrients and the standardized ileal digestibility (SID) of amino acids (AA) in SBE fed to growing pigs without or with the addition of an enzyme mixture. Eight ileal-cannulated barrows (30 ± 1.3kg initial body weight) were randomly assigned to 1 of 4 dietary treatments in a replicated 4 × 4 Latin square design to give eight replications per treatment. Samples from two batches of SBE produced under the same processing conditions were used to prepare four dietary treatments that included one of the two batches of SBE (SBE-1 and SBE-2) as the sole source of AA and fed either without or with an enzyme mixture supplementation. All diets contained titanium dioxide (3g/kg) as an indigestible marker. Pigs were given a daily feed allowance equal to 4% of their body weight for each 9-day experimental period, which included a 5-day adaptation phase and 2 days each for fecal and ileal digesta sample collection. The SID of AA was calculated using previously determined values for ileal endogenous AA losses. Data analysis was performed using the MIXED procedures of SAS. No interactions were observed between the different batches and the enzyme mixture supplementation on the ATTD of energy and nutrients and the SID of AA. There were no differences in ATTD of energy and nutrients and SID of AA between SBE-1 and SBE-2. The enzyme mixture supplementation did not impact the ATTD of energy, nutrients, or AA digestibility, except for an increase (P < 0.05) in the SID of tryptophan. The SBE-1 had a greater (P < 0.05) standardized ileal digestible phenylalanine concentration, while SBE-2 had greater (P < 0.05) standardized ileal digestible methionine, tryptophan, and cysteine concentrations. In conclusion, the addition of an enzyme mixture did not affect the digestibility of energy, nutrients, or AA except for tryptophan in SBE when fed to growing pigs. Different batches of SBE may have varying feeding values due to differences in standardized ileal digestible AA concentrations.