Hello, my name is Charmaine Espinosa and I’ll be presenting results of some of the experiments we have conducted at the University of Illinois looking at how conditioning and expansion increase the nutritional value of soybean expellers.

Soybean is a legume that belongs to the oilseed crop category, and is the most important agricultural protein crop in animal feeding. The oil from soybean is refined for food or industrial uses, whereas the remaining meal portion can be fed to domestic and livestock animals or can be exported to be used in industrial applications.

Oil can be removed from soybeans using solvent extraction or the extruder-expeller method. If oil is extracted from soybeans via solvent extraction, the resulting co-product is soybean meal, and if oil is extracted from soybeans via the mechanical expeller method, the resulting co-product is soybean expellers. Soybean expellers contain 42 to 43% CP in contrast to conventional SBM which contains approximately 46 to 48%. However, the concentration of fat in soybean expellers is 6 to 8% which and this concentration is greater compared with that of conventional SBM, and this may result in soybean expellers having greater digestibility of AA than soybean meal.

Soy products contain trypsin inhibitors, which negatively affect nutrient digestibility, feed efficiency, and health status of the animals. For this reason, heat is usually applied to inactivate trypsin inhibitors and other heat-labile anti-nutritional factors, and subsequently improve nutrient digestibility in soy products. After extracting the oil from soybeans, the resulting soybean expellers may undergo steam conditioning and expansion, and these processing technologies can inactivate trypsin inhibitors. Therefore, different types and degrees of expansion and conditioning conditions may influence concentrations and digestibility of energy and AA in soybean expellers, however data to demonstrate this are limited.

Thus, two experiments were conducted to test the hypothesis that conditioning and expansion increases the standardized ileal digestibility of AA, as well as values for digestible energy and metabolizable energy in soybean expellers.

Four soybean expellers were used for the 2 experiments. The first source of soybean expellers, which is the L-1 soybean expellers, was produced by removing the oil from soybeans using cold extraction. This source was not further processed, and therefore, the L-1 soybean expellers is a non-heat-treated soybean expellers. 
The second source of soybean expellers, the L-2 soybean expellers, was produced by removing the oil from soybeans using cold extraction, and this followed by short-term conditioning for 60 s at 90 ºC, followed by expansion at 110 ºC. 
L-3 soybean expellers was produced via cold extraction of oil from raw soybeans, followed by short-term conditioning for 60 s at 90 ºC, then long-term conditioning for 12 min at 100 ºC, followed by expansion at 110 ºC. 
And the last source of soybean expellers, the L-4 soybean expellers, was produced by also removing the oil from raw soybeans via cold extraction, followed by short-term conditioning for 60 seconds at 90 ºC, long-term conditioning for 48 min at 100 ºC, and expansion at 110 ºC. 
Before conducting the 2 experiments, the 4 sources of soybean expellers were analyzed for trypsin inhibitors. This graph shows the trypsin inhibitor activity in 4 soybean expellers, where the yellow bar represents the L-1 soybean expellers; orange bar, the L-2 soybean expellers; blue bar, L-3 soybean expellers, and the red bar represents the L-4 soybean expellers- and what we can observe in the graph is that the application of conditioning and expansion was able to reduce the trypsin inhibitor activity from 34 mg/g to 2.4 mg/g. With that in mind, it is our objective to determine how reducing trypsin inhibitors thru conditioning and expansion influences nutrient digestibility in soybean expellers.
Therefore, the first experiment was designed to determine the standardized ileal digestibility of AA in 4 sources of soybean expellers.
Ten growing pigs with an initial body weight of 54 kg that had a T-cannula installed in the distal ileum were used, and these pigs were housed in individual pens. A total of five diets were prepared. Each source of soybean expellers was included in one diet as the only source of AA, and a N-free diet was formulated to measure basal endogenous losses of AA. Pigs were allotted to a 5 × 4 Youden square design with five diets and four periods. Two pigs were assigned to each diet within each period; therefore, there were eight replicate pigs per diet. Each experimental period lasted 7 days. The initial 5 day of each period was considered an adaptation period. Ileal digesta samples were collected on days 6 and 7.
Moving on with the results, this graph shows the standardized ileal digestibility of Lys, Met, Thr, and Trp in 4 sources of soybean expellers. Here we can observe that the digestibility of indispensable AA in non-heat-treated soybean expellers (which is the L-1 soybean expellers) was less than in heat-treated soybean expeller. The digestibility of AA in L-2 soybean expellers was also less than in L-3 or L-4 soybean expellers.
Same result was observed for the digestibility of branched-chain amino acids where here we can observe that the digestibility of branched-chain amino acids can be increased by at least 10 percentage units if short-term conditioning and expansion were applied in soybean expellers. However, if short-term conditioning, long-term conditioning, and expansion were applied, the SID of AA in soybean expellers can be increased by at least 45 percentage units. This indicates that heat treatment is necessary to increase digestibility of AA in soybean expellers. The observation that L-2 soybean expellers had reduced AA digestibility compared with L-3 or L-4 soybean expellers indicates that the processing conditions applied in L-2 soybean expellers was not sufficient to completely ameliorate the negative effect of trypsin inhibitors. Therefore, it appears that long-term conditioning must be applied to completely inactivate trypsin inhibitors and subsequently increase digestibility of AA in soybean expellers.
Now that we demonstrated that further processing of soybean expellers increases AA digestibility, we then wanted to test the hypothesis that conditioning and expansion increase the concentrations of DE and ME in soybean expellers.

A corn-based diet and four diets containing corn and each source of soybean expellers were formulated; thus, a total of five diets were prepared. Forty barrows with an initial body weight of 17.5 kg were randomly allotted to the five diets with eight replicate pigs per diet. Pigs were housed individually in metabolism crates that allow for the total, but separate, collection of urine and fecal materials. The initial 5 days was considered the adaptation period to the diet, whereas urine and fecal materials were collected during the following 4 days using the marker-to-marker approach. These samples were analyzed for gross energy to enable us to calculate for apparent total tract digestibility of GE, and the concentration of DE and ME of each source of soybean expellers were calculated using the difference procedure.

Moving on with the results, this graph shows the apparent total tract digestibility of GE in 4 sources of soybean expellers. Here we can observe that the digestibility of GE in non-heat-treated soybean expellers was less than in heat-treated soybean expellers, and the digestibility of GE in heat-treated soybean expellers was not different.

The observed reduction in digestibility of GE in non-heat-treated soybean expellers also resulted in reduced concentrations of DE and ME in non-heat-treated soybean expellers compared with heat-treated soybean expellers. To the best of our knowledge, data demonstrating the effect of heat treatment on the energy values in soybean expellers have not been reported. Therefore, the observed energy reduction in the concentrations of DE and ME in non-heat-treated soybean expellers most likely due to the presence of heat-labile anti-nutritional factors. Trypsin inhibitors has been demonstrated to reduce the availability of digestible AA in soybean expellers, which may have subsequently resulted in a reduction in the concentration of DE and ME in non-heat-treated soybean expellers.
Based on the results from the two experiments, we have demonstrated that the DE and ME as well as the SID of AA in non-heat-treated soybean expellers were less than in heat-treated soybean expellers, this indicates that heat treatment must be applied to increase nutrient availability in soybean expellers. In the first experiment, we also observed that the AA digestibility in L-2 soybean expellers was less than in L-3 or L-4 soybean expellers; thus, the application of short-term conditioning (60 s) at 90 ºC is not enough to inactivate trypsin inhibitors in soybean expellers. Therefore, long-term conditioning must be applied to completely inactivate trypsin inhibitors and subsequently increase digestibility of AA in soybean expellers. Also the obtained values for AA digestibility, DE, and ME were not different between L-3 and L-4 soybean expellers. 
Therefore, this indicates that 12 min of long-term conditioning at 100 ºC must be applied to completely inactivate trypsin inhibitors and subsequently maximize the digestibility of energy and AA in soybean expellers.
We would like to take this opportunity to acknowledge Evonik for their inputs and financial support.
And also to the whole team of Stein Monogastric Nutrition Laboratory. Thank you for your interest in this presentation and if you would like to know more about other research topics in nutrition, you can always visit our website at nutrition.ansci.illinois.edu.