Fase IV: Planificación

Since the 1990’s, pretreated SBM has been under increasing investigations. SBM has been processed via heat treatment (Hancock et al., 1990), extrusion (Burnham et al., 2000, Qiao et al., 2003), purification (Hancock et al., 1989), enzyme treated (Jones et al., 2018), and microbial fermentation (Hong et al., 2004). The microbial fermentation process utilizes an increased quantity of proteases to partially degrade large proteins and increase nutrient absorption in the duodenum and jejunum (Feng et al., 2007b).

Furthermore, the fermentation of SBM has been reported to increase the bioavailability of nutrients (Hotz and Gibson, 2007) and decrease soybean anti-nutritional factors

(Egounlety and Aworh, 2003), thus creating the potential for increased digestibility and growth performance in nursery pigs (Walker et al., 1986, Zhang et al., 2013). Cervantes- Pahm and Stein (2010) reported that both fermented and enzymatically treated SBM contained increased quantities of small peptides and digestible AA than conventional SBM. However, fermented and enzymatically treated SBM did not contain a higher SID or AID of AA (excluding Lys) when compared to conventional SBM and/or FM

(Cervantes-Pahm and Stein, 2010). Hong et al. (2004) reported similar findings, but also reported that the SID of some essential AA were higher in fermented SBM than

AA from a fungal-processed SBM were comparable to those of FM in both 10 kg and 30 kg pigs, supporting its continued usage beyond the nursery phase and into grow-finisher diets. In accordance with AA digestibility, treated SBM is a viable alternative to

conventional SBM and/or FM.

Favorable results have been obtained from fermented SBM treated with bacteria and/or fungus. A variety of microorganisms have been used in the processing of SBM; a complete list has been provided in a review by Mukherjee et al. (2016). The diversity found in processing species can vary the resultant products (Frias et al., 2008). Both fungal and bacterial species have been used to obtain processed SBM with varied levels of improved nutritional advantages. However, fungal Aspergillus has become the most widely used microorganism for feed fermentation processes.

Aspergillus species produce participating enzymes that include hemicellulases,

hydrolases, proteases, amylases, lipases, and tannases (Pinto et al., 2001, Mathivanan et

al., 2006). Some of the Aspergillus species that have been used in the fermentation

process include A. oryzae (Feng et al., 2007a, Feng et al., 2007b, Liu et al., 2007), A.

usamii (Hirabayashi et al., 1998), A. awamori (Kishida et al., 2000), A. niger

(Mathivanan et al., 2006). A. oryzae has been reported to completely eliminate trypsin inhibitors from SBM (Feng et al., 2007b, Liu et al., 2007). Furthermore, it has been reported to reduce stachyose and raffinose, while eliminating sucrose for the production of α-galactosidases (Cervantes-Pahm and Stein, 2010). The fungal breakdown of

carbohydrates often results in the increase in nutritive value reported in fermented SBM products, namely increases in crude fat, crude ash, dry matter, and CP (Hong et al., 2004, Feng et al., 2007a, Feng et al., 2007b). Liu et al. (2007) reported an increase in average

daily gain, average daily feed intake, serum phosphorus, serum IgM and serum IgA after feeding A. oryzae-treated feed to young pigs. However, fungal species are not the only candidate capable of creating these advantageous results from fermented SBM.

Many bacterial species have been used in SBM fermentation. These species are able to decrease SBM’s anti-nutritional factors and increase the nutritive value of the end-products. Bacterial species, such as Bacillus subtilis and Lactobacillus plantarum, can decrease overall protein size, which increasing absorption within non-ruminant digestive tracts. B. subtilis increases the availability of several amino acids, but a

decrease in proline was reported as a limitation to its usage (Teng et al., 2012). Bacterial fermentation increases antioxidant properties of SBM (Amadou et al., 2011). Song et al. (2008) reported that L. plantarum and Bifidobacterium lactis significantly reduced the allergenic effects of soy proteins. Similar to fungus, bacteria-based fermentation can yield reductions in anti-nutritional factors and increases in nutrient availability in young pigs. However, the different processing agents have varying production requirements in temperature and metabolic substrate that ultimately change the final product values and responses in animal models. Therefore, the final decision involved in choosing which processing microorganisms to use depends on the desired nutrient profile desired for the final product.

An experimental microbially-enhanced SBM (MSBM) has been under investigation at South Dakota State University (SDSU). MSBM was created from a unique incubation process involving a yeast-like strain of Aureobasidium pullulans. A.

pullulans is a common yeast-like fungus that occurs within a diverse array of

potential to increase various enzymes (i.e. amylase, protease, lipase, cellulase, xylanase) that become biologically relevant within feed processing and other niche markets as reviewed by Gaur et al. (2010). However, its use in the fermentation of SBM was

originally investigated as a replacement for FM in aquaculture diets. MSBM was reported to contain lower levels of anti-nutritional factors and a higher AA digestibility than conventional SBM in fish. Sinn et al. (2016) investigated and reported MSBM as a viable alternative to FM in weaned pig diets. The inclusion of MSBM in the diet can pose as a replacement for FM without compromising growth performance and/or health (Sinn et

al., 2016, Koepke et al., 2017). Furthermore, pigs fed a diet containing MSBM had

reduced incidence and severity of PWD (Sinn et al., 2016). Therefore, it has been suggested that the microbiome may act as a primary contributor to the improved growth performance and health parameters observed in prior studies (Sinn et al., 2016, Koepke et

al., 2017).