Diets with high inclusion of corn fermented protein (CFP) may have an excess of Leu, which has a negative impact on the growth performance of pigs. Tryptophan is a precursor of serotonin, which is a neurotransmitter that is critical for feed intake regulation, and excess dietary Leu may reduce synthesis of serotonin in the brain by preventing Trp from being transported to the brain. Reduced serotonin synthesis can result in reduced feed intake and pigs with reduced feed intake due to excess Leu also have reduced growth performance. As a consequence, if diets are formulated based on CFP instead of soybean meal (SBM), diets need to be fortified with extra Trp to account for the reduced efficiency of Trp due to the excess Leu in corn protein. However, a quantitative assessment of how much extra Trp is needed in diets based on CFP instead of SBM has not been conducted. Therefore, an experiment was conducted to test the hypothesis that the optimum Trp:Lys ratio in diets for growing pigs is greater if CFP rather than SBM is used as the protein source in the diets. 

Soybean meal (SBM) is the primary source of amino acids (AA) and energy in diets for swine throughout the world. However, less SBM is often used in diets to decrease nitrogen (N) excretion and environmental pollution. Nonetheless, it is demonstrated that lowering dietary protein does not consistently deliver the same performance of pigs as of pigs fed high protein diets, even though all indispensable AA meet the requirements of pigs. It is possible that soybean-derived bioactive compounds (i.e., soy isoflavones and saponins) in SBM act as immunomodulators, which improve the performance of pigs. It is also possible that low-protein diets contain N below the requirements for pigs to maximize growth. However, no data are available to prove this hypothesis. Therefore, the objective of this experiment was to test the hypothesis that N balance of pigs is not affected by reducing dietary protein if soy isoflavones or N source are supplemented in diets.

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.

To reduce the cost of pork production, high-fiber ingredients are often used in diets, but an increase in the amount of dietary fiber in pig diets may have a negative impact on the digestibility of nutrients and energy. Carbon footprint from pork production is related to emissions of greenhouse gases including carbon dioxide, nitrous oxide, and methane from pigs. Emission of gases may be correlated with the composition of feeds, and it is thus possible that feeding pigs with diets containing high-fibrous feed ingredients affects the gas exchange, which also impacts concentration of net energy (NE) in diets.

Therefore, the objective of this experiment was to test the null hypothesis that feeding pigs with a high-fiber diet does not affect gas production, N excretion, and NE in diets fed to group-housed pigs.

Apparent ileal digestibility (AID) of amino acids (AA) is affected by dietary AA levels because of different contributions of endogenous AA to the ileal digesta from pigs fed diets with different levels of AA. Because of the influence of dietary protein and AA on calculated values for AID, values for AID obtained in individual feed ingredients are not always additive in mixed diets. Therefore, values for standardized ileal digestibility (SID) of AA, which are corrected for the basal ileal endogenous losses of AA, are used in diet formulations to avoid the influence of endogenous AA on digestibility values, and SID values are, therefore, additive in mixed diets.

When the direct procedure is used to determine AA digestibility, diets containing cereal grains are sometimes formulated to contain AA below the requirement. In contrast, if the SID of oilseed meals or other protein-rich ingredients are determined, concentrations of AA may be at or above the requirement. Because the influence of the basal endogenous losses of AA is eliminated in the calculations of SID values, it is assumed that values for SID are not influenced by dietary concentrations of AA. However, to our knowledge this hypothesis has not been experimentally verified, but it is an important question because it may influence how diets used in digestibility experiments are formulated. Therefore, four experiments were conducted to test the hypothesis that the SID of AA by growing pigs is not influenced by dietary AA levels.

Particle size reduction in cereal grains often results in an improved digestibility of starch due to increased surface area of grains, which subsequently increases the interaction with digestive enzymes. Improvement in the apparent total tract digestibility (ATTD) of gross energy (GE) upon particle size reduction has also been demonstrated in corn and a number of other ingredients when fed to weanling or growing-finishing pigs.

Protein quality has relied on methods such as PDCAAS. However, the Food and Agriculture Organization has proposed a new method called DIAAS to better assess protein quality in human foods using the pig as a model. This shift is crucial, not only for optimizing diets, but also for understanding the nutritional value of protein-rich foods. According to the DIAAS method, protein claims can only be made for foods with a score above 75. In general, animal-based foods are considered high quality proteins with score above 75 or 100, being, in most cases, complete proteins that can complement lower quality proteins such as plant-based proteins. Meats, eggs, and fish are examples of high quality proteins, however, salmon proteins are also available, and use of by-products in human consumption has been increasing due to their nutritional value and versatility. Novel sources of salmon proteins such as salmon hydrolysate that may be used in human nutrition have been developed. Salmon hydrolysate proteins contain more than 68% crude protein (CP) and are highly digestible food ingredients, but limited information demonstrating the protein quality of these products is available. Therefore, the objectives of this study were to determine the standardized ileal digestibility (SID) of amino acids (AA) and the digestible indispensable amino acid score (DIAAS) for salmon proteins when fed to growing pigs.

Arabinoxylans are the predominant fiber component in cereal grains and cereal co-products. They have a backbone of β-(1− 4) linked xylose units with side chains of arabinose, glucuronic acid, acetyl, and phenolic acids. Xylanase hydrolyzes the β-(1− 4) glycosidic bonds between xylose units in the backbone and releases a mixture of xylose and xylo-oligosaccharides that can be either absorbed or fermented by pigs. Previous data indicate that xylanase increased the degradation of dietary fiber and increased energy digestibility in diets for growing pigs and lactating sows. Xylo-oligosaccharides improve growth performance of nursery pigs because they serve as prebiotics that modulate gut microbiota. A stimbiotic (i.e., xylanase in combination with xylo-oligosaccharides) may improve growth performance of weanling pigs to a greater extent than either additive alone by shifting the intestinal microbiome to favor fiber fermentation. However, there are no data on possible effects of xylanase in sows diets on growth performance and intestinal health of the offspring or on the impact of the stimbiotic on digestibility of nutrients when fed to nursery pigs. Therefore, an experiment was conducted to test the hypothesis that xylanase or a stimbiotic improves growth performance and the apparent total tract digestibility (ATTD) of dry matter (DM), gross energy (GE), and total dietary fiber (TDF), and the concentration of digestible energy (DE) of diets for weanling pigs, but that the effect is greater in offspring of sows fed xylanase in lactation than in offspring of sows not fed xylanase.

Protein malnutrition is a serious problem in both underdeveloped countries and the U.S., where many children and elderly people don't get enough protein. To determine the quality of food proteins, experts use a method called digestible indispensable amino acid score (DIAAS), which measures how well the body can digest the amino acids in a food item. The FAO recommended this method in 2011. According to the DIAAS method, protein claims can only be made for foods with a score above 75. Eggs are rich in protein and essential amino acids needed for muscle development and bodily functions. However, it's important to consider how eggs are cooked, as different methods can affect the availability of amino acids. Eggs are often eaten with other foods, and it's believed that the high-quality protein in eggs can make up for the lower quality of protein in plant ingredients when eaten together, but more research is needed to confirm this. Therefore, the objectives of this experiment were to determine DIAAS for eggs cooked in different forms and in traditional egg-style combinations with breads or hash brown, and test the hypothesis that protein quality in eggs can compensate for the low protein quality of plant-based ingredients and that DIAAS in different combined meals is additive.