Tryptophan is an indispensable AA that is often limiting for growth in pigs fed corn-soybean meal-based diets. Tryptophan may act as a regulator of feed intake by enhancing serotonin signaling in the brain, because Trp is a precursor for serotonin. High Trp intake increases feed intake, and this is partly attributed to increased serotonin synthesis. Availability of dietary Trp in the brain is considered the rate-limiting step in hypothalamic serotonin synthesis. However, to be transported into the brain, Trp competes with other large neutral AA such as Val, Leu, Ile, Tyr, and Phe for a common transporter (L-type AA transporter 1) to cross the blood-brain barrier.

Most diets for weanling pigs contain highly digestible plant and animal proteins, but there is an increasing trend to include more fibrous co-products in diets for pigs due to reduced diet costs. However, feeding diets to nursery pigs with high concentration of dietary fiber may reduce nutrient digestibility, induce intestinal inflammation, and subsequently depress growth performance. Addition of 100 to 200 mg/kg of Cu from Cu hydroxychloride (IntelliBond C^II; Micronutrients USA LLC; Indianapolis, IN) to diets improves feed efficiency and reduces post weaning diarrhea in pigs. However, there are at this point no data to demonstrate the effect of Cu hydroxychloride on intestinal barrier integrity of pigs fed low-fiber or high-fiber diets, and it is not known if Cu hydroxychloride influences immune responses of pigs. Therefore, 2 experiments were conducted to test the hypothesis that inclusion of 150 mg/kg of Cu from Cu hydroxychloride reduces intestinal permeability and subsequently improves growth performance of pigs fed diets without or with high concentration of dietary fiber.

Supplementing Cu to diets fed to pigs at 100 to 250 mg/kg may reduce post-weaning scouring and also improve ADG and ADFI. Addition of Cu at 250 mg/kg in diets for pigs containing 5% animal fat improved growth performance, and it was speculated that this is due to the ability of Cu to improve animal fat utilization and enzymatic activity. Inclusion of 45 mg/kg of dietary Cu in diets for rabbits improved body mass gain by upregulating mRNA transcription of fatty acid transport protein, fatty acid binding protein, and carnitine palmitoyl transferase 1, indicating that dietary Cu may influence post-absorptive metabolism of lipids. However, the effect of supplementing dietary Cu on post-absorptive lipid metabolism in pigs remains inconclusive. Therefore, an experiment was conducted to test the hypothesis that addition of 150 mg/kg Cu from Cu hydroxychloride (IntelliBond C^II; Micronutrients USA LLC; Indianapolis, IN) to a diet based on corn, soybean meal (SBM), and distillers dried grains with solubles (DDGS) improves growth performance of pigs, and that dietary Cu influences mRNA abundance of genes involved in post-absorptive metabolism of lipids in pigs.

Kwon Woong B., Kevin J. Touchette, Aude Simongiovanni, Kostas Syriopoulos, Anna Wessels, Hans H. Stein. 2019. Effects of dietary leucine concentration on branched-chain amino acid metabolism in growing pigs. Journal of Animal Science, Volume 97, Issue Supplement_2, July 2019, Pages 65–66. (Abstr.). Link to abstract.

Kwon, W. B., and H. H. Stein. 2019. Excess leucine reduces nitrogen retention, growth performance in pigs. July 29, 2019. Link to ful text.

Soybean meal (SBM) is one of the most important protein sources in swine diets. However, SBM has high concentrations of non-digestible oligosaccharides, mainly stachyose, raffinose, and verbascose, which may increase diarrhea incidence and reduce nursery growth performance. Fermex 200 (Purina Animal Nutrition, Shoreview, MN, USA) is a new source of fermented SBM that may serve as an alternative to other protein sources in diets fed to pigs. However, there are at this point no data for effects of Fermex 200 on growth performance and amino acid (AA) digestibility when fed to weanling pigs.

Therefore, 2 experiments were conducted to test the hypothesis that the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA in Fermex 200 are greater than in conventional SBM. The second hypothesis was that Fermex 200 supports growth of weanling pigs as well as other protein sources.

Diarrhea is one of the main problems for pigs during the post-weaning period. Traditionally, antibiotic growth promoters have been used to control post-weaning diarrhea, but consumers are increasingly concerned about this practice and there is therefore an interest in feeding diets that contain no antibiotics. However, feeding pigs without antibiotic growth promoters requires alternative strategies to control post-weaning diarrhea, but feeding low protein diets may be one way to reduce the incidence of post-weaning diarrhea. However, there is a lack of knowledge about consequences of reducing the protein level in diets fed to weanling pigs.

Feeding low protein diets to pigs results in increased net energy in the diet, reduced water intake by pigs, and reduced nitrogen excretion. This will result in reduced volume of manure and also reduced concentrations of ammonium in manure. However, if formulation of low protein diets results in feeding diets with concentrations of indispensable AA that are below the requirements, deposition of protein in pigs may be greater and deposition of fat may be increased compared with pigs fed a diet containing higher level of protein. However, it is not known if feeding a diet low in protein to weanling pigs also results in changes in carcass characteristics of market pigs.

Therefore, the objective of this experiment was to test the hypothesis that feeding a low-protein diet to pigs during the post-weaning period will result in reduced diarrhea during this period, but no effects on growth performance from wean to finish and no changes in carcass composition of pigs when they reach market weight.

Requirements for P for growing pigs are expressed as the requirement for standardized total tract digestible (STTD) P, whereas requirements for Ca are usually expressed as requirements for total Ca. It is, however, recognized that diets for pigs are most accurately formulated based on a STTD Ca:STTD P ratio, and recent work has generated values for STTD of Ca in most Ca containing feed ingredients, which makes it possible to formulate diets based on STTD Ca.

Recent data from the University of Illinois have indicated that if STTD P is at the requirement, a ratio between STTD Ca and STTD P that is less than 1.35:1, 1.25:1, and 1.10:1 maximizes growth performance of pigs from 25 to 50 kg, 50 to 85 kg, and 100 to 130 kg, respectively. However, the STTD Ca:STTD P ratio needed to maximize bone ash is greater than the ratio needed to maximize growth performance. An attempt to estimate the requirement for STTD Ca by pigs from 11 to 25 kg was also made, but due to a reduction in ADG and G:F as dietary Ca increased, an optimal STTD Ca:STTD P ratio could not be estimated.

Calcium may be absorbed by transcellular or paracellular transport. Transcellular transport is the primary route if dietary Ca is low, but if dietary Ca is adequate or high, Ca is mainly absorbed using the paracellular route via the tight junctions. However, there are limited data demonstrating effects of dietary Ca concentration on abundance of genes related to transcellular and paracellular transport of Ca in the small intestine of pigs.

Therefore, the objectives of this experiment were to test the hypotheses that a STTD Ca:STTD P ratio less than 1.40:1 maximizes growth performance of pigs from 11 to 25 kg and that increasing dietary Ca downregulates abundance of genes related to transcellular absorption of Ca and tight junction proteins in the small intestine.

Sorghum is used as an alternative to corn due to its lower cost and wide availability. However, conventional sorghum contains high concentration of tannin and phytate, which act as antinutritional factors. Use of microbial phytase may hydrolyze phytate and subsequently improve P absorption. High-lysine sorghum is a new variety of sorghum which may be comparable to other cereal grains and may serve as alternative to corn for pigs. However, there are at this point no data for effects of adding phytase to diets containing sorghum and no data to demonstrate the nutritional value of high-lysine sorghum.

Therefore, 2 experiments were conducted to test the hypothesis that inclusion of 500 phytase units (FTU)/kg of microbial phytase improves the standardized total tract digestibility (STTD) of P in sorghum varieties. The second hypothesis was that the STTD of P, as well as concentrations of digestible energy (DE) and metabolizable energy (ME) in high-lysine sorghum is not different from that of corn and other sources of sorghum.