Ruiz-Arias, N. C.,  S. A. Lee, H. H. Stein. 2025. There are only minor differences among soybeans grown in different areas of the United States in nutrient composition and digestibility of amino acids by growing pigs. Animal Feed Science and Technology 323 (2025) 116297. doi.org/10.1016/j.anifeedsci.2025.116297. Link to full text.

Values for digestible energy (DE) and metabolizable energy (ME) in feed ingredients are usually determined in growing pigs and subsequently applied to all groups of pigs. Results of recent research, however, indicate that the energy content of soybean meal (SBM) is greater than previously thought when fed to growing pigs. This increase in energy may be due to changes in the pigs themselves or differences in methodology, but there are no recent experiments assessing DE and ME in SBM when fed to sows. Therefore, it remains unclear if sows also have greater DE and ME in SBM compared with current book values. Likewise, there are no recent data for the DE and ME in soybean hulls although soybean hulls are often added to diets for gestating sows. Therefore, an experiment was conducted to test the hypothesis that gestating and lactating sows have greater DE and ME in SBM and soybean hulls than growing pigs and that DE and ME in SBM fed to both growing pigs and sows are greater than current book values. The second hypothesis was that there is no difference in apparent total tract digestibility (ATTD) of gross energy (GE) and DE between gestating and lactating sows.

Nelson, Megan E., Su A Lee, Carrie L. Walk, April Zhang, Heng-Xiao Zhai, Hans H. Stein. 2025. Digestibility of calcium in calcium carbonate varies among origins, but is increased by microbial phytase regardless of origin. Animal Feed Science and Technology 320 (2025) 116230. doi.org/10.1016/j.anifeedsci.2025.116230 Link to full text.

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.

Ruiz-Arias, N. C., S. A Lee, and H. H. Stein. 2024. Full-fat soybeans: Valuable source of energy, digestible P for pigs. National Hog Farmer. On-line edition. Oct. 31, 2024. Link to full text.

Ibagon, Jimena A., Su A. Lee, Diego A. Rodriguez, C. Martin Nyachoti, Hans H. Stein. 2024. Reduction of particle size of field peas (Pisum sativum L.) increases net energy and digestibility of starch when fed to growing pigs, but there is no difference in  nutritional value between peas from the United States and peas from Canada. J. Anim. Sci.

Marshall, C. M., S. A Lee, and H. H Stein. 2024. Feed preference of weanling pigs fed diets containing extruded corn ground to different particle sizes. J. Anim. Sci.102 (Suppl. 3): 234–235. doi.org/10.1093/jas/skae234.272 Link to abstract.

Vitamin D regulates a wide spectrum of genes responsible for Ca and P homeostasis and cell differentiation. Cholecalciferol, commonly known as vitamin D₃, is a primary source of vitamin D₃ in diets for growing pigs; however, it needs to be hydroxylated twice to be active. The first hydroxylation occurs in the liver at the 25-position, resulting in 25-hydroxycholecalciferol [25(OH)D₃], whereas the second hydroxylation occurs in the kidneys at the 1-position, resulting in 1,25 dihydroxycholecalciferol [1,25(OH)₂D₃], which is the active form of vitamin D₃ in the body. Supplementation of 25(OH)D₃ to diets for sows in late gestation may increase the apparent total tract digestibility (ATTD) and retention of Ca and P, but there are no data to demonstrate this effect in growing pigs.

Cereal grains commonly used in diets for pigs have low digestibility of P because P is bound to phytate. Exogenous phytase increases the digestibility of both Ca and P in pigs by releasing the P from the phytate molecule within the gastrointestinal tract of pigs. However, there is limited information about the interaction between 25(OH)D₃ and supplemental phytase in diets fed to growing pigs. Therefore, the objective of this experiment was to test the hypothesis that both 25(OH)D₃ and microbial phytase independently and in combination may increase standardized total tract digestibility (STTD) of Ca and P by growing pigs.