The use of synthetic amino acids (AA) in diets for pigs has increased in the past few decades due to increased availability and reduced prices of these AA. The increased use of synthetic AA has caused a reduced need for inclusion of soybean meal (SBM) in diets. For instance, a common grower pig diet without synthetic AA needs around 35% SBM to full fill the requirements for all indispensable AA, but a diet with 5 synthetic AA only requires 17% SBM. It has generally been assumed that pigs fed diets containing synthetic AA will have growth performance, protein deposition, and carcass quality that is no different from that of pigs fed diets based in which the majority of the AA are furnished by SBM as long as the requirements for all digestible AA are met. It has also been assumed that diets formulated with large amounts of synthetic AA, compared with diets based on SBM provide more net energy to pigs because these diets contain more corn and less SBM. However, some of these assumptions are not based on strong scientific evidence, and results of recent research has raised doubts about previously assumed effects of using synthetic AA. Therefore, the objective of this experiment was to test the hypothesis that the use of synthetic AA instead of some of the intact protein from SBM does not impact growth performance, carcass composition, energy deposition, blood cytokines or abundance of intestinal amino acid transporters when fed to growing pigs.

Synthetic amino acids (AA) are often included in diets fed to pigs at the expense of SBM or other protein sources to provide a portion of the indispensable AA needed by pigs. Substituting SBM for synthetic AA may support pig growth performance, but daily N retention by pigs may be reduced if diets containing synthetic AA instead of some of the SBM are used. This indicates that there may either be an AA deficiency in diets with synthetic AA, or there are factors other than AA in SBM that are needed to maximize protein synthesis in pigs.

It has been speculated that synthetic AA are absorbed more rapidly than AA from intact protein, which may impair protein synthesis. It is, therefore, possible that if protein from SBM is replaced by synthetic AA, some of the synthetic AA will not be used for protein synthesis, which will result in reduced nitrogen retention by the pigs. Results of recent research also indicate that the DE in SBM is greater than in corn, and therefore, dietary DE may be reduced if SBM is reduced in the diet. However, at this time, no research has been conducted to confirm this assumption. Therefore, the objective of this experiment was to test the hypothesis that use of synthetic AA instead of some of the intact protein from SBM reduces N retention and also reduces DE of the diet if fed to growing pigs.

Stein, Hans H. Jimena A. Ibagon, Minoy Cristobal. 2024. Soybean meal or crystalline amino acids in diets for growing pigs: Impact on diet net energy, pig growth performance, and nitrogen retention. Proc. 23^nd Annual Midwest Swine Nutrition Conf. Danville, IN, Sep. 5, 2024. Pages 45-51.

Cristobal, Minoy, Su A Lee, Leidy J. Torres-Mendoza, Andrea P. Mallea, Carl M. M. Parsons, Hans H. Stein. 2024. Effect of feeding intact protein from soybean meal instead of crystalline amino acids on energy and nitrogen balance by growing pigs. J. Anim. Sci Vol. 102, Suppl. S2. P 283 - 284. doi.org/10.1093/jas/skae102.322. Link to abstract.

Mallea, Andrea P., Su A Lee, Minoy Cristobal, Leidy J. Torres-Mendoza, Hans H. Stein. 2024. Supplementation of valine, isoleucine, and tryptophan may overcome the negative effects of dietary excess leucine in high protein corn protein when fed to weanling pigs. J. Anim. Sci. Vol. 102, Suppl. S2. P 34 - 35. doi.org/10.1093/jas/skae102.041 Link to abstract.

Cristobal, M., J. Blair, P. L. Utterback, H. H. Stein, and C. M. Parsons. 2023. Determination of TME_n, standardized amino acid digestibility, and phosphorus digestibility in soybean expellers produced from a new variety soybeans fed to chickens. Poultry Sci. 102 (E-suppl. 1): 37. Link to abstract.

Cristobal, Minoy A., Carl M. M. Parsons, Hans H. Stein. 2023. Concentrations of Digestible and Metabolizable Energy, Ileal Digestibility of Amino Acids, and Digestibility of Phosphorus in a New Variety of Soybeans Fed to Growing Pigs. J. Anim. Sci. Volume 101, Issue Supplement 2, Pages 51 - 52, doi.org/10.1093/jas/skad341.056. Link to abstract.

Soybean meal (SBM) is the major source of amino acids (AA) and energy in diets for swine throughout the world. However, due to the emergence of feed-grade crystalline AA, it is estimated that SBM usage by pigs has been reduced by at least 35% over the last 25 years. Reduction on concentration of SBM and increasing the use of crystalline AA in diets may impact the digestibility of crude protein (CP) and AA. Therefore, the objective of this experiment was to test the hypothesis that diets containing corn, SBM, and crystalline AA have greater AA digestibility compared with corn and SBM diets.

Soybean meal is the principal amino acid (AA) source in diets for pigs and it also supplies a considerable amount of metabolizable energy close to what is found in corn. However, new varieties that have different characteristics are sometimes developed and an example of such a new variety is the Photoseed variety of soybeans that captures more carbon and sunlight leading to a more nutrient rich ingredient and a reduced footprint from crop production. There is, however, no information about the nutritional value of the soybean meal produced from the Photoseed variety of soybeans. Therefore, the objective of this research was to test the hypothesis that the concentration of digestible energy (DE) and metabolizable energy (ME) are not different in soybean expellers produced from Photoseed soybeans compared with control soybeans when fed to pigs.