The growing area within the United States has only minor impact on digestible and metabolizable energy, and standardized total tract digestibility of phosphorus in full-fat soybeans fed to growing pigs

Two experiments were conducted to test the hypothesis that there is no difference in the digestible energy (DE), the metabolizable energy (ME), or the standardized total tract digestibility (STTD) of P among five sources of full-fat soybeans (FFSB) fed to growing pigs. The five sources of FFSB (source 01, 02, 03, 04, and 05) were collected from five different states in the United States and fed to growing pigs. In experiment 1, forty-eight pigs (initial body weight: 30.86 ± 1.64 kg) were placed in metabolism crates and allotted to six diets using a randomized complete block design with eight replicate pigs per diet. A basal diet based on corn as the only source of energy and five diets containing corn and each source of FFSB were formulated. Pigs were fed experimental diets for 13 days and feces and urine were collected for four days after seven days of adaptation. Results demonstrated that ME in corn was 15.73 MJ per kg dry matter (DM), and ME in the five sources of FFSB was 20.74, 19.85, 20.59, 20.19, and 21.22 MJ ME per kg DM, respectively. In experiment 2, eighty pigs (initial body weight: 16.73 ± 3.16 kg) were housed individually in metabolism crates and allotted to a randomized complete block design with 10 diets and 8 replicate pigs per diet. Five diets contained each source of FFSB as the only source of P and five additional diets were formulated by adding 1000 phytase units (FTU)/kg of microbial phytase to the original five diets. Thus, the experiment was a 5 × 2 factorial with the five sources of FFSB and two levels of microbial phytase (i.e., 0 or 1000 FTU per kg diet). Feces were collected from pigs for four days following five days of adaptation. Results demonstrated that there were no interactions between phytase and source of FFSB, and no effects of phytase or source of FFSB were observed for feed intake, weight of feces excreted, or daily basal endogenous P loss. The STTD of P in the diet with FFSB source 05 was greater (P < 0.05) than the STTD of P in the other sources of FFSB if no phytase was used, but when phytase was added to the diets, no differences among the five sources of FFSB were observed (interaction, P < 0.05). However, the STTD of P was greater (P < 0.05) if phytase was used than if no phytase was used. In conclusion, results demonstrated that there were only minor differences among sources of FFSB in ME and STTD of P in FFSB was not different among the five sources if microbial phytase was used.