Soybean meal is the most commonly used protein source in swine diets in the United States. In addition to conventional soybeans, researchers have bred varieties of soybeans to meet various nutritional needs of pigs. For example, soybeans low in oligosaccharides have been developed for feeding to weanling pigs, who cannot digest the oligosaccharides in conventional soybeans and may suffer reduced performance and even illness as a result. High protein soybean varieties have also been developed.

Existing information on the nutritional value of high protein and low oligosaccharides soybean varieties in swine diets is incomplete. There is no difference in digestible energy, metabolizable energy, or digestibility of crude protein and amino acids between non-dehulled high protein full fat soybeans (FFSB-HP) and non-dehulled conventional full fat soybeans (FFSB-CV). There are, however, no data on the digestibility of protein, amino acids, and energy in dehulled FFSB-HP, although most soybeans are de-hulled prior to being used in diets fed to pigs. Similarly, there is no difference in digestible and metabolizable energy or amino acid digestibility between soybean meals produced from low oligosaccharide soybeans and conventional varieties, but there are no data on values for low oligosaccharide full fat soybeans (FFSB-LO).Therefore, two experiments were conducted to determine standardized ileal digestibility (SID) of amino acids as well as values for digestible and metabolizable energy in de-hulled conventional, high protein, and low oligosaccharide full fat soybeans.

Three sources of dehulled full fat soybeans were used. These sources included FFSB-CV, FFSB-LO, and FFSB-HP (Table 1).

Eight growing barrows with an average initial body weight of 20.6 kg were equipped with a T-cannula in the distal ileum and then randomly allotted to a replicated 4 × 4 Latin square design. Four diets were formulated. Three of the diets contained one of each variety of full fat soybeans, and the last diet was a N-free diet that was used to calculate basal endogenous losses of amino acids and crude protein. Ileal digesta were collected and analyzed to determine apparent ileal digestibility (AID) of protein and amino acids. AID values were corrected for basal endogenous losses to calculate standardized ileal digestibility values.

The digestibility of crude protein and all amino acids did not differ between FFSB-CV and FFSB-LO (Table 2). In addition, no difference in the digestibility of arginine, histidine, methionine, tryptophan, glutamic acid, and proline was observed among the three samples. However, digestibility values for isoleucine, leucine, lysine, phenylalanine, valine, alanine, glycine, and tyrosine, along with the means of indispensable and all amino acids, were less (P < 0.05) in FFSB-HP than in FFSB-CV, but did not differ from FFSB-LO. For tryptophan, aspartic acid, cysteine, and serine, digestibility was less (P < 0.05) in FFSB-HP than in both FFSB-LO and FFSB-CV. These results indicate that amino acid digestibility is not compromised if FFSB-LO are used rather than FFSB-CV, but if FFSB-HP is used, the digestibility of some amino acids may be slightly reduced. However, because of the greater concentration of amino acids in FFSB-HP than in FFSB-CV, pigs will absorb more amino acids if FFSB-HP are used.

A total of 24 growing barrows with an average initial body weight of 28.3 kg were allocated to a randomized complete block design and fed one of four diets. One diet was based on corn, and the other three diets each contained one of the sources of FFSB in addition to corn. Corn and soybeans were the only sources of energy in these diets.  Urine and fecal materials were collected and used to calculate the digestible and metabolizable energy content of the feed ingredients.

No difference was observed  in the concentrations of digestible and metabolizable energy among the three tested varieties of soybeans (Table 3). DE and ME values for all soybeans were greater than DE and ME in corn.

• The digestibility of crude protein and amino acids in low oligosaccharide full fat soybeans did not differ from conventional soybeans.
• The digestibility of crude protein and most amino acids in high protein full fat soybeans was less than in conventional soybeans, but the digestibility of arginine, histidine, methionine, tryptophan, glutamic acid, and proline did not differ between the two sources.
• Concentrations of digestible and metabolizable energy did not differ among conventional, low-oligosaccharide, and high protein  varieties of soybeans.
• The concentration of digestible and metabolizable energy is greater in full fat soybeans than in corn.

Table 1. Composition of full fat soybeans (FFSB-CV), high protein full fat soybeans (FFSB-HP), and high protein-low oligosaccharide full fat soybeans (FFSB-LO)

¹TIU = trypsin inhibitor units.

Table 2. Standardized ileal digestibility (SID) of CP and AA in conventional full fat soybeans (FFSB-CV), high protein full fat soybeans (FFSB-HP), and high protein-low oligosaccharide full fat soybeans (FFSB-LO) by growing pigs

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

Table 3. Concentration of energy in corn, conventional full fat soybeans (FFSB-CV), high protein full fat soybeans (FFSB-HP), and high protein-low oligosaccharide full fat soybeans (FFSB-LO)

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

This report is based on unpublished research by J. Yoon and H. H. Stein.