Cristobal, M., P. L. Utterback, H. H. Stein, C. M. Parsons. 2025. True metabolizable energy, standardized amino acid digestibility, and digestibility of phosphorus in soybean expellers produced from conventional or high-oil varieties of soybeans fed to chickens. Poultry Science 104 (2025) 104726.  doi.org/10.1016/j.psj.2024.104726 Link to full text.

Soybean meal (SBM) is the major source of amino acids (AA) and energy in diets for swine throughout the world because SBM has an AA profile that matches the requirements of pigs and AA in SBM have high digestibility. In the U.S., nearly 20% of all SBM produced is used to feed pigs. However, AA in diets can also be provided by feed-grade synthetic AA and diets based on corn and synthetic AA have been thought to also increase diet net energy and reduce N excretion and carbon footprint. With the addition of synthetic AA in diets, it is possible to reduce the inclusion of SBM and formulate diets with reduced crude protein. However, recent data indicate that pigs of modern genotypes utilize more dietary protein than older genotypes and the net energy may, therefore, not be increased in diets that contain less SBM and more corn and synthetic AA. Therefore, the objective of this experiment was to test the hypothesis that diets based on corn and SBM and limited quantities of synthetic AA contain net energy that is not different from diets based on corn and larger quantities of synthetic AA.

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.

Fanelli, Natalia S., Juliana C. F. R. Martins, and Hans H. Stein. 2024. The digestible indispensable amino acid score (DIAAS) in eggs and egg-containing breakfast meals is greater than in toast breads or hash browns served without eggs. Journal of Nutritional Science (2024), vol. 13, e68, page 1 of 11. doi:10.1017/jns.2024.71. Link to full text.

Most of the P in corn and soybean meal (SBM) is stored as phytate. Phytase consists of one hydroxylated inositol ring with six phosphate groups. Therefore, phytase is often included at a standard level of 500 units (FTU) per kg in swine diets to increase the release of P from phytate. However, greater concentrations of phytase in diets for pigs may benefit growth and feed efficiency, which is likely a result of the inositol that is also released and can be absorbed by pigs. Inositol is believed to increase growth of animals by stimulating protein accretion. Inositol also improves gut health of pigs by enhancing intestinal epithelial cell functions. However, data from recent research demonstrated that weaning pigs at around 21 days of age results in a dramatic drop in plasma inositol and it is not until 6 weeks post-weaning that pigs will regain preweaning levels of inositol. Therefore, an experiment was conducted to test the hypothesis that microbial phytase will release sufficient inositol from corn and SBM and other ingredients in diets for newly weaned pigs to maintain pre-weaning levels of plasma inositol throughout the post-weaning phase and that this will result in improved growth performance of pigs.

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.

Stein, H.H. 2024. Review: Aspects of digestibility and requirements for minerals and vitamin D by growing pigs and sows. Animal 18, 101125. doi.org/10.1016/j.animal.2024.101125  Link to full text.

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.