40 Phosphorus digestibility in short-season corn and roasted full-fat soybean fed to growing pigs without or with exogenous enzymes.

Abstract The aim was to determine the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of phosphorus (P) in short-season corn (SSC) and roasted full-fat soybean (RFFS) fed to growing pigs with or without phytase and a multi-carbohydrase complex (MC). In Experiment 1, 18 male pigs (16.3 ± 1.25 kg) were assigned to one of three dietary treatments, with six replicates per diet. The diets included a control SSC diet, SSC + 1,000 phytase units/kg (SSC+Phy), and SSC + 1,000 phytase units/kg + 600 units/kg of MC (SSC+Phy+MC). Corn was the solo source of P in mixed diets. In Experiment 2, 24 male pigs (16.0 ± 1.29 kg) were assigned to one of four diets: a basal diet (BD) based on corn and soybean meal, BD + 40% RFFS (RFFS), BD + 40% RFFS + 1,000 phytase units/kg (RFFS+Phy), and BD + 40% RFFS + 1,000 phytase units/kg + 1,200 units/kg of MC (RFFS+Phy+MC). Pigs were housed individually in metabolism crates for 12 d (7-day adaptation, 5-day fecal collection) and fed at 2.8 times their maintenance energy requirement. Ingredients, diets, and fecal samples were analyzed for dry matter and P content. Data were analyzed using the GLIMMIX procedure in SAS, considering the random effect of blocks (weight and repetition over time) and the fixed effect of treatments, with the individual pig as the experimental unit. SSC and RFFS ingredient contained 0.25 and 0.56% total P, 0.19 and 0.22% phytate, giving 21.1 and 11.0% phytate-bound P of total P, respectively. For SSC-based diets, phytase reduced fecal P excretion (P < 0.05) and increased ATTD and STTD of P (P < 0.01), regardless of MC inclusion. The ATTD of P was 18, 55, and 54%, and STTD was 24, 61, and 60% for the SSC, SSC+Phy, and SSC+Phy+MC diets, respectively. For RFFS-based diets, P intake was higher (P < 0.01) for RFFS and RFFS+Phy diets compared to BD. The inclusion of RFFS increased (P < 0.01) ATTD (38 vs. 51%) and STTD (42 vs. 55%) of P compared to BD. The ATTD of P was 51, 67 and 67%, and STTD was 55, 71 and 71% for RFFS, RFFS+Phy, and RFFS+Phy+MC diets, respectively. The ATTD and STTD of P in RFFS ingredient were 70 and 73%, respectively. Phytase increased (P < 0.01) both ATTD and STTD of P in RFFS-containing diets, with no effect of MC supplementation. In conclusion, 1,000 FTU of phytase improved P digestibility in SSC- and RFFS-based diets, but no synergistic effect was observed with MC supplementation. The ingredients ATTD and STTD of P 18 and 24% for SSC, and 70 and 73% for RFFS ingredient, respectively.