Evaluation of fermented soybean meal sources in diets for Evaluation of fermented soybean meal sources in diets for nursery pigs nursery pigs

Summary A total of 296 mixed-sex pigs (PIC 327 × 1050; 14.5 ± 3.0 lb BW and 21 d of age) were used in a 31-d experiment evaluating the effect of further processing methods for soybean meal on weanling pig growth performance. There were 11 replicate pens per treatment with 6 or 7 pigs per pen. At weaning, pigs were allotted to pens by initial weight to 1 of 4 treatments in a completely randomized design. Experimental treatments were: (1) negative control (NC: no specialty protein sources), (2) fermented soybean meal processing method 1 (FSBM 1), (3) fermented soybean meal processing method 2 (FSBM 2), and (4) enzymatically treated soybean meal (ETS). The specialty soybean meal protein sources were included in Phase 1 (d 0 to 7) and Phase 2 (d 7 to 20) diets at 5%, and diets were formulated to the same standardized ileal digestible (SID) amino acid level. All pigs were subsequently fed a common diet during Phase 3 (d 20 to 31). Phase 1 and 2 diets were fed in pellet form, whereas the Phase 3 common diet was fed in meal form. Nutrient analyses of specialty soybean meal ingredients were conducted and generally matched those used for diet formulation. From d 0 to 7, pigs fed FSBM 2 had increased ( P < 0.05) ADG and BW compared with pigs fed ETS, whereas those fed NC and FSBM 1 were intermediate. No other differences were observed between treatments for growth or BW during the experimental period, common period, or overall. In summary, further processed soybean meal sources did not improve nursery pig growth compared with traditional soybean meal.


Introduction
Newly weaned pigs have limited ability to utilize plant protein sources because of their relatively immature digestive systems.This is why specialty animal protein sources are frequently used in diets as a source of readily available protein and amino acids; however, the high cost associated with the animal by-products creates a need for an economical plant-derived specialty protein source.
Traditional soybean meal contains high levels of intact proteins, which are not readily available to pigs' immature digestive system.Research has indicated that pigs fed fermented rather than solvent-extracted soybean meal have improved nutrient digestibility.Soybean meal fermented in the presence of Aspergillus oryzae and Bacillus subtilis (FSBM) may be used in diets fed to weanling pigs in place of specialty animal proteins without negatively affecting ME or NE of the diet or the standardized ileal digestibility

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(SID) of amino acids (Rojas and Stein, 2013 3 ; Cervantes-Pahm 2010 4 ).The fermentation process is thought to reduce trypsin inhibitors and some oligosaccharides that have been shown to decrease pig performance, but most research has indicated that soy proteins cannot fully replace animal protein sources postweaning and maintain equal pig growth performance (Jones et al., 2008 5 ).Consequently, the objective of this study was to determine the impact of partially replacing conventional soybean meal with fermented or enzymatically treated soybean meal on nursery pig growth performance.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment.The trial was conducted at the K-State Swine Teaching and Research Center in Manhattan, KS.
A total of 296 mixed-sex pigs (PIC 327 × 1050; 14.5 ± 3.0 lb BW and 21 d of age) were used in a 31-d experiment.There were 11 replicate pens per treatment with 6 or 7 pigs per pen.At weaning, pigs were allotted to pens by initial weight to 1 of 4 dietary treatments in a completely randomized design.Each pen (4 ft × 5 ft) contained a 4-hole, dry self-feeder and a nipple waterer to provide ad libitum access to feed and water.
The four dietary treatments were: (1) negative control (NC: no specialty protein sources), (2) fermented soybean meal processing method 1 (FSBM 1), (3) fermented soybean meal processing method 2 (FSBM 2), and (4) enzymatically treated soybean meal (ETS).Both FSBM products were manufactured using solid-state fermentation.FSBM processing methods differed from a previous experiment (see "Effects of PepSoy-Gen Processing Method on Nursery Pig Growth Performance," p. 27) because separate patented bacteria strains were utilized in the fermentation process.FSBM 1, FSBM 2, and ETS were included at 5% in the treatment diets.Nutrient profiles and SID amino acid digestibility coefficients for FSBM 1 and FSBM 2 were provided by the manufacturer.The SID amino acid coefficients for ETS were from NRC (2012 6 ).
A three-phase diet (Table 1) series was used with treatment diets fed during Phase 1 (d 0 to 7) and Phase 2 (d 7 to 20), and a common diet was fed during Phase 3 (d 20 to 31).All diets were manufactured at the K-State O.H. Kruse Feed Technology Innovation Center.Phases 1 and 2 were fed in pelleted form, whereas the common diet was provided in meal form.Experimental protein sources were provided by Nutraferma (North Sioux City, SD) and shipped to Kansas State University prior to diet manufacturing.All specialty proteins were analyzed for amino acid profile and proximate analysis (Table 2) at the University of Missouri Agricultural Experiment Station Chemical Laboratories (Columbia, MO).Diet samples were collected from the feeders for each dietary phase and sent for proximate analysis (Table 3) at Ward Laboratories, Inc.
Results were analyzed as a completely randomized design.One replicate pen from the NC treatment was determined to be an outlier (F/G > 2 SD from the mean) on d 7, and this data point was therefore removed from the dataset.Treatment means were analyzed using the LSMEANS statement with pen as the experimental unit.Least squares means were calculated for each independent variable, and means were considered significant at P < 0.05 and tendencies at 0.05 < P < 0.10.

Results and Discussion
Nutrient analyses (Table 3) of experimental diets generally matched formulated levels for CP and amino acids.Given the similar nutrient content between FSBM 1 and FSBM 2, it is unlikely that any growth performance differences observed between processing methods are due to differences in essential amino acid concentrations.
For Phase 1 (d 0 to 7), pigs fed FSBM 2 had improved (P < 0.05; Table 4) ADG compared with ETS, whereas pigs fed the NC and FSBM 1 diets were intermediate.No differences in ADFI or feed efficiency were detected across treatments.Accordingly, pigs fed FSBM 2 were heavier (P < 0.05) than those fed ETS at d 7.During Phase 2 (d 7 to 20) and the common diet period (d 20 to 31), no growth performance differences were observed between treatment, and pig weights were similar on d 14, 20, and 31.Overall (d 0 to 31), there were no significant differences between treatments for ADG, ADFI, or feed efficiency.
Although the greater ADG seen for FSBM 2 compared with ETS in Phase 1 appears promising within treatments containing specialty proteins, the lack of a response in Phase 2 and overall appears to indicate a limited impact of processing method on overall nursery performance.Moreover, in the present study, pigs fed a negative control diet without specialty proteins performed similarly to those fed diets containing various further-processed soybean meal products.Many studies have demonstrated growth benefits when incorporating high-quality animal protein sources in early nursery diets.This benefit is thought to be the result of reducing the amount of soybean meal that may contain less digestible nutrients or anti-nutritional factors for the young pig; however, the present study failed to indicate any benefit of additional soybean meal processing to improve performance compared with pigs fed diets containing traditional soybean meal.Nevertheless, the postweaning period remains challenging for the young pig and warrants further investigation of plant-based protein source alternatives.

Table 2 .
Nutrient analysis of basal ingredients (as-fed basis) 1

Table 3 .
Nutrient analysis of experimental diets (as-fed basis) 1

Table 4 .
Effects of soybean meal further processing method on nursery pig growth performance1,2