Ibagon, Jimena A., Su A Lee, Hans H. Stein. 2026. Reducing dietary crude protein for gestating and lactating sows reduces daily nitrogen retention, but reproductive performance is not impacted by diet protein concentration. Journal of Animal Science and Biotechnology 7:125 

Canola meal and soybean meal (SBM) are the most commonly used sources of amino acids in diets for swine. However, via genetic selection, varieties of canola with greater concentrations of crude protein and reduced concentrations of fiber have been identified. Following oil extraction, the resulting high-protein canola meal (CM-HP) contains 3 to 5 % more crude protein than conventional canola meal (CM-CV). It is, therefore, expected that CM-HP contains more digestible and metabolizable energy than CM-CV, but this hypothesis has not been experimentally verified (Liu et al., 2016). Therefore, it is the objective of this experiment to determine the apparent total tract digestibility (ATTD) of energy and concentrations of digestible energy (DE) in CM-HP, CM-CV, and SBM when fed to lactating sows.

Soybean meal (SBM) is commonly used as a source of amino acids in swine diets because of its high protein content (Kudelka et al., 2021).  In addition, SBM contributes with energy and phosphorus (P). However, high portion of the P in SBM is bound to phytate, which is indigestible by pigs. Therefore, microbial phytase enzyme is supplemented in swine diets. The impact of phytase on the digestibility of P is well documented, however some experiments on digestibility in corn–SBM diets has been reported energy increase if microbial phytase was used (Liao et al., 2005; Arredondo et al., 2019; Lala et al., 2020; Espinosa et al., 2022), but, not in others (She et al., 2018; Mesina et al., 2019; Lamp and Moritz, 2022). There is, however, a lack of information about the impact of microbial phytase on the digestibility of energy in SBM. It is also not known if a possible effect of microbial phytase on energy digestibility in SBM is consistent among different sources of SBM.

Canola meal and soybean meal (SBM) are the most commonly used sources of amino acids in diets for swine. However, via genetic selection, varieties of canola with greater concentrations of crude protein and reduced concentrations of fiber have been identified. Following oil extraction, the resulting high-protein canola meal (CM-HP) contains 3 to 5 % more crude protein than conventional canola meal (CM-CV). It is, therefore, expected that CM-HP contains more digestible and metabolizable energy than CM-CV when fed to sows, but this hypothesis has not been experimentally verified (Liu et al., 2016). Therefore, it was the objective of this experiment to determine the apparent total tract digestibility (ATTD) of energy and concentrations of digestible energy (DE) and metabolizable energy (ME) in high protein canola meal, conventional canola meal, and SBM when fed to gestating sows.

Cristobal, Minoy, Su A Lee , Carl M. Parsons, and Hans H. Stein.

Soybean meal (SBM) is the primary plant-protein source in diets for pigs and provides both amino acids (AA) and energy to the diets. Current estimates for net energy in SBM are less than for cereal grains, based on the assumption that there is more nitrogen to be deaminated if ingredients are high in protein because deamination and excretion of nitrogen via the urea cycle are energy-requiring processes, and therefore, reduce energy efficiency. It has been suggested that pigs retain only 45 to 50% of absorbed nitrogen, which corresponds to 40 to 45% of ingested nitrogen. Modern genotypes of pigs, however, have improved the capacity for protein synthesis and may retain more nitrogen than older genotypes, which would result in less AA deamination and, therefore, less energy loss to deaminate AA and excrete nitrogen. Indeed, results of recent research indicate that pigs fed corn-SBM based diets retain more than 60% of ingested nitrogen, indicating that protein retention by modern genotypes of pigs is more efficient than by older genotypes. It is likely that as breeding companies have selected for leaner pigs, they have also selected genotypes that are more efficient in converting dietary protein into body protein. It is, however, not known if the greater nitrogen retention that has been recently reported is experienced by all pigs regardless of body weight (BW) and if it is true for all types of diets regardless of the dietary level of protein. Therefore, the objective of this experiment was to test the hypothesis that nitrogen retention, measured as a percent of nitrogen consumed, is greater than 50% regardless of the dietary protein level and the BW of pigs.

Cristobal, Minoy, Su A Lee, Carl M. Parsons, and Hans H. Stein. 2025. Replacement of soybean meal in diets for growing pigs with corn and synthetic amino acids results in reduced energy and nitrogen digestibility and reduced daily nitrogen retention, but metabolizable energy is not changed. Journal of Animal Science, 2025, 103, skaf197.

Kim, Yeonwoo, Su A Lee, Hans H. Stein. 2025. Comparative digestibility of energy and concentrations of energy in corn, soybean meal, and soybean hulls fed to growing pigs and gestating and lactating sows. Journal of Animal Science, Volume 103, Issue Supplement_1, May 2025, Pages 282–283, doi.org/10.1093/jas/skaf102.314 Link to abstract.

Mallea, A. P., S. A Lee, and H. H. Stein. 2025. Could soybean meal and high levels of phytase aid pigs in the post-weaning period?. National Hog Farmer. On-line edition. May 29, 2025. Link to full text.