Soybean meal (SBM) is one of the most important protein sources in swine diets. However, most P in SBM is bound to phytate, which increases inclusion of inorganic P in diets for pigs. Use of microbial phytase may hydrolyze phytate and subsequently improve P absorption. Fermex 200 (Purina Animal Nutrition, Shoreview, MN, USA) is a new source of fermented SBM that may serve as an alternative to other protein sources in diets fed to pigs. However, there are at this point no data for effects of adding phytase to diets containing Fermex 200 and no data for digestible energy (DE) and metabolizable energy (ME) concentrations of Fermex 200.

Therefore, 2 experiments were conducted to test the hypothesis that inclusion of 1,000 phytase units (FTU)/kg of microbial phytase improves the standardized total tract digestibility (STTD) of P in conventional SBM and Fermex 200. The second hypothesis was that the STTD of P, as well as concentrations of DE and ME in Fermex 200 are greater than in conventional SBM.

Experimental design

Conventional SBM was sourced from the same batch of SBM used to produce Fermex 200. The conventional SBM and Fermex 200 used in the 2 experiments originated from the same batches. (Table 1).

Experiment 1: Phosphorus Digestibility

Forty barrows (initial BW: 11.0 ± 1.4 kg) were housed individually in metabolism crates and randomly allotted to 2 diets and 2 levels of microbial phytase (0 or 1,000 FTU/kg) in a randomized complete block design. There were 10 replicate pigs per diet. Diets were based on Fermex 200 or conventional SBM as the sole source of P and these diets either contained no microbial phytase or 1,000 FTU/kg of phytase. Feces were collected using the marker to marker approach with 5-d adaptation and 4-d collection periods. Basal endogenous loss and STTD of P in experimental diets were calculated based on intake and fecal and urine output of P.

Experiment 2: Energy Measurements

Twenty four barrows (initial BW: 14.2 ± 1.2 kg) were housed individually in metabolism crates and allotted to a corn-based diet or 2 diets that contained corn and conventional SBM or corn and Fermex 200. Each diet was fed to 8 pigs. Feces and urine samples were collected using the marker to marker approach with 5-d adaptation and 4-d collection periods. Samples were analyzed for gross energy (GE) to calculate for the apparent total tract digestibility (ATTD) of GE, as well as concentrations of DE and ME in each diet. The DE and ME values in conventional SBM and Fermex 200 were calculated using the difference procedure.

Results

Experiment 1: Phosphorus Digestibility

Pigs fed the conventional SBM diets had reduced excretion of P in feces when phytase was added, but that was not the case for pigs fed the Fermex 200 diets (Table 2; interaction, P < 0.01). When phytase was not included in diets, the STTD of P was greater in Fermex 200 than in conventional SBM. However, addition of microbial phytase to the diets increased the ATTD and STTD of P in diets containing conventional SBM, but not in Fermex 200 diets (interaction, P < 0.01).

Experiment 2: Energy Measurements

The ATTD of GE was not different among ingredients (Table 3). However, the concentration of DE on an as-fed basis was greater (P < 0.05) in conventional SBM than in corn, but not different from Fermex 200. On a DM basis, concentration of DE in conventional SBM tended to be greater (P < 0.10) than in corn, but ME values were not different among ingredients. 

Key points

• The STTD of P was greater in Fermex 200 than in conventional SBM if microbial phytase was not added to diets.
• Addition of microbial phytase improved the STTD of P in conventional SBM, but not in Fermex 200.
• The concentrations of DE and ME in Fermex 200 were not different from conventional SBM.

Table 1. Analyzed nutrient composition of ingredients (as-fed basis)

¹Fermex 200 = fermented soybean meal (Purina Animal Nutrition, Shoreview, MN, USA).

²AEE = acid hydrolyzed ether extract.

³IDF = insoluble dietary fiber; SDF = soluble dietary fiber; TDF = total dietary fiber.

⁴Calculated as 28.2% of phytic acid

⁵Calculated as total P – phytate P.

Table 2. Effects of microbial phytase on standardized total tract digestibility (STTD) of P in Fermex 200 and conventional soybean meal, Exp. 1¹

¹Data are means of 10 observations per treatment.

²Fermex 200 = fermented soybean meal (Purina Animal Nutrition, Shoreview, MN, USA).

³The microbial phytase used was Ronozyme HiPhos (10,000 phytase units per gram; DSM, Kaiseraugst, Switzerland); FTU = phytase units.

⁴EPL = basal endogenous P loss. This value was assumed to be 190 mg/kg DMI (dry matter intake). The daily basal EPL (mg/d) for each diet was calculated by multiplying the EPL (mg/kg DMI) by the daily DMI of each diet.

⁵Values for STTD were calculated by correcting values for ATTD for the basal endogenous loss of P.

Table 3. Apparent total tract digestibility (ATTD) of gross energy (GE), and concentrations of digestible energy (DE) and metabolizable energy (ME) in corn, Fermex 200, or conventional soybean meal, Exp. 2¹ 

¹Data are least squares means of 8 observations per treatment.

²Fermex 200 = fermented soybean meal (Purina Animal Nutrition, Shoreview, MN, USA).

^a-b Means within a row lacking a common letter are different (P < 0.05).

^x-y Means within a row lacking a common letter are tended to differ (P < 0.10).