Evaluation of elevated soybean meal diets with inclusion of exogenous enzymes on the effect of growth performance and digestibility

Abstract Forty-eight crossbred gilts (52.55 ± 4.12 kg) were used to evaluate the effect of high soybean meal (SBM) inclusion with dietary enzymes on growth and nutrient balance. Two sets of 24 gilts were placed in metabolism stalls and randomly assigned to one of six dietary treatments (8 pigs/trt). Experimental diets were fed in two, 12-d phases, urine and feces were collected for 72 h to assess nutrient digestibility and retention. Diets included: 1) negative control diet (NC, corn-soy (22% SBM) + synthetic AA, 2) positive control diet, (PC, 41% SBM replacing synthetic lysine), 3) PC + xylanase (WX), 4) PC + multi-enzyme (VP, hemicellulase and pectinase), 5) PC + WX + VP (WXVP), and 6) PC + 1500 FYT/kg phytase (SD). All but SD contained 600 FYT/kg phytase. Data were analyzed as repeated measures in SAS 9.4 (Statistical Analysis System, Cary, NC) with treatment, phase, and block as fixed effects and pig served as the experimental unit. Growth did not differ across treatments (P ≥ 0.13). Apparent total tract digestibility (ATTD) of DM and GE were unaffected (P ≥ 0.10), ash ATTD increased in high SBM diets (P < 0.01). Intake of nitrogen (N), phosphorus (P), calcium (Ca), and sulfur (S) increased with high SBM (HSBM) diets compared to NC (P < 0.01). Digestibility of nitrogen (N), phosphorus (P), and sulfur (S) increased in pigs fed HSBM diets (P < 0.01), while calcium (Ca) digestibility and retention were greatest in the PC and elevated phytase diets compared to the NC (P < 0.01). Absolute retention of N, P, and S was greater in higher SBM diets (P ≤ 0.02), though enzyme inclusion had minimal effects. Diet WX was intermediate with other HSBM treatments and NC for N retention (P < 0.01), WXVP was intermediate with other HSBM treatments and NC for P and S retention (P ≤ 0.02). Total N excretion was greater in WX, VP, and WXVP vs NC (P = 0.01), while enzyme supplemented diets did not differ from each other, PC and SD showed intermediate excretion levels similar to NC. Intake and digestibility of S and P increased with higher SBM, without increasing S and P excretion (P ≥ 0.12). Total Ca excretion was greater in WXVP vs VP (P = 0.03). Digestible and metabolizable energy values were similar across treatments (P ≥ 0.22). In conclusion, increasing SBM by 19% did not affect weight gain but increased intake and retention of N, P, Ca, and S, while dietary enzyme inclusion provided limited benefits in corn-soy diets, except for SD, which significantly improved Ca retention.