Feeding Value of Experimental Soybeans
Two experiments were conducted to determine amino acid digestibility and levels of digestible energy (DE) and metabolizable energy (ME) in five sources of soybean meal (SBM). The five soybean meals included hexane-extracted SBM produced from high-protein soybeans (SBM-HP) and conventional soybeans (SBM-CONV), mechanically extruded-expelled SBM produced from high-protein soybeans (EE-SBM-HP), low-oligosaccharide soybeans (EE-SBM-LO), and conventional soybeans (EE-SBM-CONV). Five diets were formulated to compare SBM sources plus a N-free diet. These six treatments were used in the first experiment to determine amino acid digestibility of each meal. Twelve growing barrows (initial BW: 67.7 ± 1.34 kg) were allotted to a replicated 6 x 6 Latin square design with six periods and six diets in each square. Each period lasted seven days and ileal digesta were collected on day six and seven of each period. Results of the experiment showed that the standardized ileal digestibility (SID) of all amino acids, except tryptophan, were similar for SBM-HP and SBM-CONV, but EE-SBM-HP and EE-SBM-LO had greater (P < 0.05) SID of histidine, isoleucine, lysine, threonine and valine than EE-SBM-CONV. The SID of all indispensable amino acids in EE-SBM-HP was greater (P < 0.05) than in SBM-HP. The SID of arginine, isoleucine, leucine, and phenylalanine in EE-SBM-CONV was greater (P < 0.05) than in SBM-CONV, but the SID of tryptophan was also greater (P < 0.05) in SBM-CONV than in EE-SBM-CONV.

Experiment two was conducted to measure DE and ME in the same five sources of SBM as used in experiment one. Forty-eight growing barrows (initial BW: 38.6 ± 3.46 kg) were placed in metabolism cages and randomly allotted to six diets with eight replicates per diet. A corn-based diet and five diets based on a mixture of corn and each source of SBM were formulated. Urine and feces were collected during a five-day collection period, and values for DE and ME in each source of SBM were calculated using the different procedure. Results showed that the ME in SBM-HP tended to be greater (P = 0.10) than in SBM-CONV (4,074 vs. 3,672 kcal/kg of DM). The ME in EE-SBM-HP also tended to be greater (P = 0.10) than in EE-SBM-CONV and in EE-SBM-LO (4,069 vs. 3,620 and 3,721 kcal/kg of DM), but there was no difference in ME between extracted and extruded-expelled meals. The researchers concluded that SBM processed from high protein soybeans had a greater feeding value compared to SBM processed from soybean with conventional levels of protein because of greater concentrations of digestible amino acids and ME. They also found that extruded-expanded processed soybean meal using low-oligosaccharide soybeans had a greater concentration of most indispensable amino acids than similarly processed meal from conventional soybeans, but the concentration of ME were similar in these two meals. Results of this experiment also showed that amino acid digestibility values in extruded-expelled SBM were greater than in hexane-extracted SBM.

Baker, K.M. and H. H. Stein. 2009 Amino acid digestibility and concentration of digestible and metabolizable energy in soybean meal produced from conventional, high-protein, or low-oligosaccharide varieties of soybeans and fed to growing pigs. J. Animal Sci.87:2282-2290.

Comparing Soybean Products for Turkeys
An experiment was conducted to investigate the effects of diets containing soybean meal (SBM), soybean protein concentrate (SPC), and soybean protein isolate (SPI) on growth performance and gut function of the young turkey. A total of 812 one-day-old male turkey poults were randomly assigned to four dietary treatments, with seven pens per treatment and 29 birds per pen. The four experimental diets containing SBM, SBM-SPC, SPC, and SPI were isonitrogenous and isocaloric and contained similar amounts of total and water-soluble nonstarch polysaccharides. The content of oligosaccharides differed among the diets and averaged 2.4, 1.9, 0.9, and 0.1% for SBM, SBM-SPC, SPC, and SPI, respectively.

When compared with SBM, birds consuming the SBM-SPC and SPC diets had higher (P < 0.05) final body weight (4.32 vs. 4.45 and 4.46 kg, respectively). Incorporation of SPI as a substitute for SBM resulted in improved feed utilization from 1.76 to 1.67 (P<0.05), but did not affect the final body weight. Significant changes in cecal concentrations of short-chain fatty acids were observed and averaged 130, 103, and 89 µmol/g of digesta for the SBM, SBM-SPC, and SPC diets, respectively. This coincided with the proportional decrease in dietary oligosaccharide content from 2.4 to 0.9% and was further substantiated by a significant decrease in ileum weights. Feeding the SPI diet resulted in the lowest ileal and cecal tissue weights as well as the lowest cecal short-chain fatty acids concentration. There was no effect of diet on digesta pH, viscosity, and mucosal sucrase and maltase activities. Bacterial β-glucuronidase activity was decreased in the cecum from 0.98 to 0.60 U/g (P=0.08) with decreased dietary oligosaccharide content. The researchers concluded that partial, or almost complete, substitution of SBM with SPC suppressed the fermentation processes in the ceca and enhanced the growth rate. The substitution of SBM with SPI significantly improved feed utilization with no effect on growth rate of poults during this eight-week study.

Jankowski, J. and co-workers. 2009. The effect of diets containing soybean meal, soybean protein concentrate, and soybean protein isolate of different oligosaccharide content on growth performance and gut function of young turkeys. Poultry Sci. 88:2132-2140.