Feeding intact proteins, peptides, or free amino acids to monogastric farm animals

Release profile of amino acids encapsulated in solid lipid particles during in vitro oro-gastrointestinal digestion

Some amino acids are known to mediate immune responses through gut microbiota metabolism in both humans and monogastric animals. However, through the diet, most free amino acids are absorbed in the small intestine and only a small quantity reaches the microbiota-rich colon. To enhance microbial metabolism of amino acids and their potential health benefits, encapsulation strategies are developed for their protection and delivery to the colon. So far, the main encapsulation systems for amino acids are based on solid lipid particles, but their fate within the digestive tract has never been fully clarified. In this study, we investigated the release of various amino acids (branched-chain amino acid mixture, or lysine, or tryptophan) loaded in solid lipid particles during in vitro oro-gastrointestinal digestion mimicking the piglet. The loaded solid lipid particles were fully characterized for their composition, thermal behavior, molecular structure, crystalline state, surface morphology, and particle size distribution. Moreover, we investigated the effect of particle size by sieving solid lipid particles into two non-overlapping size fractions. We found that amino acid release was high during the gastric phase of digestion, mainly controlled by physical parameters, namely particle size and crystalline state including surface morphology. Large particle size and/or smooth ordered particle indeed led to slower and lower release. Although lipid hydrolysis was significant during the intestinal phase of digestion, the impact of the crystalline state and surface morphology was also observed in the absence of enzymes, pointing to a dominant water/solute diffusion mechanism through these porous solid lipid particles.

Changes in Rumen Microbiology and Metabolism of Tibetan Sheep with Different Lys/Met Ratios in Low-Protein Diets

In ruminants, supplementing appropriate amounts of amino acids improves growth, feed utilization efficiency, and productivity. This study aimed to assess the effects of different Lys/Met ratios on the ruminal microbial community and the metabolic profiling in Tibetan sheep using 16S rDNA sequencing and non-target metabolomics. Ninety-two-month-old Tibetan rams (initial weight = 15.37 ± 0.92 kg) were divided into three groups and fed lysine/methionine (Lys/Met) of 1:1 (LP-L), 2:1 (LP-M), and 3:1 (LP-H) in low-protein diet, respectively. Results: The T-AOC, GSH-Px, and SOD were significantly higher in the LP-L group than in LP-H and LP-M groups (p < 0.05). Cellulase activity was significantly higher in the LP-L group than in the LP-H group (p < 0.05). In the fermentation parameters, acetic acid concentration was significantly higher in the LP-L group than in the LP-H group (p < 0.05). Microbial sequencing analysis showed that Ace and Chao1 indicators were significantly higher in LP-L than in LP-H and LP-M (p < 0.05). At the genus level, the abundance of Rikenellaceae RC9 gut group flora and Succiniclasticum were significantly higher in LP-L than in LP-M group (p < 0.05). Non-target metabolomics analyses revealed that the levels of phosphoric acid, pyrocatechol, hydrocinnamic acid, banzamide, l-gulono-1,4-lactone, cis-jasmone, Val-Asp-Arg, and tropinone content were higher in LP-L. However, l-citrulline and purine levels were lower in the LP-L group than in the LP-M and LP-H groups. Banzamide, cis-jasmone, and Val-Asp-Arg contents were positively correlated with the phenotypic contents, including T-AOC, SOD, and cellulase. Phosphoric acid content was positively correlated with cellulase and lipase activities. In conclusion, the Met/Lys ratio of 1:1 in low-protein diets showed superior antioxidant status and cellulase activity in the rumen by modulating the microbiota and metabolism of Tibetan sheep.

Exploring solubility and energetics: Dissolution of biologically important l-threonine in diverse aqueous organic mixtures across the temperature range of 288.15 K to 308.15 K

This research provides a thorough investigation into the solubility behavior and solution thermodynamics of l-threonine in significant organic solvent systems. The work was done on measuring the actual solubility and subsequently calculating overall transfer solvation free energetics (∆Genergetic0i) and transfer entropies (∆St0i) at a temperature of 298.15 K. These measurements were performed as l-threonine transitioned from water to different water-organic mixed solvents systems. The saturated solubilities of l-threonine were determined using the 'gravimetric method' at five equidistant temperatures namely 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K. By analyzing the data on solubility, we further obtained the different energies involved in solvation related issues. In the case of single solvents, the nature of solubility of l-threonine was observed like: dimethylsulfoxide (DMSO) < acetonitrile (ACN) < N, N-dimethylformamide (DMF) < ethylene glycol (EG) < water (H2O), irrespective of the experimental conditions. Specifically, at 298.15 K, the solubilities of l-threonine in single solvents were found to be as follows: 0.8220 mol per kg of water, 0.3101 mol per kg of EG, 0.1337 mol per kg of DMF, 0.1107 mol per kg DMSO and 0.1188 mol per kg of ACN. This research critically examines the relationship between the experimental saturated solubility of l-threonine and the complex properties influencing its solvation energy in diverse aqueous organic solvent systems.

Dietary isoleucine supplementation enhances growth performance, modulates the expression of genes related to amino acid transporters and protein metabolism, and gut microbiota in yellow-feathered chickens

This study investigated the effects of dietary isoleucine (Ile) on growth performance, intestinal expression of amino acid transporters, protein metabolism-related genes and intestinal microbiota in starter phase Chinese yellow-feathered chickens. Female Xinguang yellow-feathered chickens (n = 1,080, aged 1 d) were randomly distributed to 6 treatments, each with 6 replicates of 30 birds. Chickens were fed diets with 6 levels of total Ile (6.8, 7.6, 8.4, 9.2, 10.0, and 10.8 g/kg) for 30 d. The average daily gain and feed conversion ratio were improved with dietary Ile levels (P < 0.05). Plasma uric acid content and glutamic-oxalacetic transaminase activity were linearly and quadratically decreased with increasing dietary Ile inclusion (P < 0.05). Dietary Ile level had a linear (P < 0.05) or quadratic (P < 0.05) effect on the jejunal expression of ribosomal protein S6 kinase B1 and eukaryotic translation initiation factor 4E binding protein 1. The relative expression of jejunal 20S proteasome subunit C2 and ileal muscle ring finger-containing protein 1 decreased linearly (P < 0.05) and quadratically (P < 0.05) with increasing dietary Ile levels. Dietary Ile level had a linear (P = 0.069) or quadratic (P < 0.05) effect on the gene expression of solute carrier family 15 member 1 in jejunum and solute carrier family 7 member 1 in ileum. In addition, bacterial 16S rDNA full-length sequencing showed that dietary Ile increased the cecal abundances of the Firmicutes phylum, and Blautia, Lactobacillus, and unclassified_Lachnospiraceae genera, while decreased that of Proteobacteria, Alistipes, and Shigella. Dietary Ile levels affected growth performance and modulated gut microbiota in yellow-feathered chickens. The appropriate level of dietary Ile can upregulate the expression of intestinal protein synthesis-related protein kinase genes and concomitantly inhibit the expression of proteolysis-related cathepsin genes.

Carbohydrate-active enzymes in animal feed

Considering an ever-growing global population, which hit 8 billion people in the fall of 2022, it is essential to find solutions to avoid the competition between human food and animal feed for croplands. Agricultural co-products have become important components of the circular economy with their use in animal feed. Their implementation was made possible by the addition of exogenous enzymes in the diet, especially carbohydrate-active enzymes (CAZymes). In this review, we describe the diversity and versatility of microbial CAZymes targeting non-starch polysaccharides to improve the nutritional potential of diets containing cereals and protein meals. We focused our attention on cellulases, hemicellulases, pectinases which were often found to be crucial in vivo. We also highlight the performance and health benefits brought by the exogenous addition of enzymatic cocktails containing CAZymes in the diets of monogastric animals. Taking the example of the well-studied commercial cocktail Rovabio™, we discuss the evolution, constraints and future challenges faced by feed enzymes suppliers. We hope that this review will promote the use and development of enzyme solutions for industries to sustainably feed humans in the future.

Standardized amino acid digestibility and protein quality in extruded canine diets containing hydrolyzed protein using a precision-fed rooster assay

Protein hydrolysate has become a choice of alternative protein source in canine diets as it showed greater digestibility, lower allergenic responses, and various functional properties when compared with intact proteins. The objective of the study was to determine the effect of hydrolyzed protein inclusion on amino acid digestibility and protein quality in extruded canine diets when compared with a traditional protein source for adult dogs. Five treatment diets were formulated to have similar compositions except for the main protein source. The control diet was formulated with chicken meal (CM) as the primary protein source. Test hydrolyzed proteins, chicken liver and heart hydrolysate (CLH) and chicken hydrolysate (CH) were used to partially or completely substitute CM. The diets were: CONd: CM (30%) diet; 5%CLHd: 5% CLH with 25% CM diet; CLHd: CLH (30%) diet; 5%CHd: 5% CH with 25% CM diet; CHd: CH (30%) diet. A precision-fed rooster assay was used to determine standardized amino acid digestibility for the ingredients and diets. In addition, Digestible Indispensable Amino Acid Score (DIAAS)-like values were calculated for the protein ingredients. All protein ingredients had higher than 80% of digestibility for all indispensable amino acids with no difference among sources (P > 0.05). From the DIAAS-like values referencing AAFCO nutrient profile for adult dogs, CLH and CH did not have any limiting amino acid; on the other hand, CM has a lower DIAAS-like value (93.3%) than CLH and CH (P < 0.05) with tryptophan being the first-limiting amino acid. The DIAAS-like values were often lower when the amino acid combinations methionine + cysteine and phenylalanine + tyrosine were included in the calculation. When referencing NRC recommended allowances and minimal requirements, methionine was the first-limiting amino acid for all protein sources. Amino acid digestibility was mostly above 80% and comparable among the treatment diets. Regarding the digestible indispensable amino acid concentrations in the diets, all of them met the AAFCO nutrient profile for adult dogs at maintenance. In conclusion, both protein hydrolysates were highly digestible, high-quality protein sources, and a full substitution from CM to protein hydrolysate could result in greater protein quality, according to the DIAAS-like values of the ingredients, when compared with CM in extruded canine diets.

Effects of lowering dietary protein content without or with increased protein-bound and feed-grade amino acids supply on growth performance, body composition, metabolism, and acute-phase protein of finishing pigs under daily cyclic heat stress

This study investigated the effects of a low-protein diet with or without an increase in dietary protein and feed-grade amino acids (AAs) on the growth performance, body composition, metabolism, and serum acute-phase proteins of finishing pigs reared in thermoneutrality or cyclic heat stress conditions. A total of 90 gilts (67.7 ± 6.2 kg) were distributed in a 2 × 3 factorial arrangement (two ambient temperatures and three diets). Ambient temperatures (AT) were thermoneutral (TN, 22 °C for 24 h) and cyclic heat stress (CHS, 12 h to 35 °C and 12 h to 22 °C). The evaluated diets (D) were high crude protein (HP); low CP-free AA-supplemented diets (LPAAs); low CP-free AA-supplemented diets and digestible Lys level (+20%), and Lys:AA ratios above recommendations (LPAA+). The experimental period lasted 48 d (two experimental phases: days 0-27 and days 28-48, respectively). CHS pigs had higher skin temperature (P < 0.05) than TN pigs. Pigs in CHS had higher rectal temperature (P < 0.05) than TN pigs until day 38 but similar (P > 0.10) to TN pigs from 38 to 45 d. For the entire experiment, CHS pigs had lower (P < 0.05) final BW, average daily gain and daily feed intake, net energy intake, body lipid, bone mineral, lipid deposition, energy retention, Lys and CP intake, and nitrogen excretion than TN pigs. The level of CP intake impacted nitrogen excretion, nitrogen retention efficiency, and urea as pigs fed HP had the highest values, and pigs fed LPAA had the lowest values (P < 0.05). On day 27, CHS pigs had lower (P < 0.05) free triiodothyronine than TN pigs. LPAA+ pigs had lower (P < 0.05) insulin than LPAA. On day 48, CHS pigs had lower (P < 0.05) thyroxine, albumin, and lactate than TN pigs. On day 27, pigs fed LPAA+ had higher (P < 0.05) lactate than pigs fed HP or LPAA. Both AT and D were enough to stimulate the immune system as CHS pigs had lower (P < 0.05) transferrin and 23-kDa protein levels than TN pigs, and HP pigs had higher haptoglobin than LPAA on day 27. These results confirm the deleterious effects of high AT on performance, body composition, metabolism, and immune system stimulation in finishing pigs. These data also show that a diet with low levels of CP can be provided to pigs in CHS without affecting performance and body composition while reducing nitrogen excretion. However, the use of a diet with an AA level above the requirements obtained by increasing intact protein and free AA did not attenuate the impact of CHS on performance and body composition of pigs.

Selective nourishing of gut microbiota with amino acids: A novel prebiotic approach?

Prebiotics are dietary substrates which promote host health when utilized by desirable intestinal bacteria. The most commonly used prebiotics are non-digestible oligosaccharides but the prebiotic properties of other types of nutrients such as polyphenols are emerging. Here, we review recent evidence showing that amino acids (AA) could function as a novel class of prebiotics based on: (i) the modulation of gut microbiota composition, (ii) the use by selective intestinal bacteria and the transformation into bioactive metabolites and (iii) the positive impact on host health. The capacity of intestinal bacteria to metabolize individual AA is species or strain specific and this property is an opportunity to favor the growth of beneficial bacteria while constraining the development of pathogens. In addition, the chemical diversity of AA leads to the production of multiple bacterial metabolites with broad biological activities that could mediate their prebiotic properties. In this context, we introduce the concept of "Aminobiotics," which refers to the functional role of some AA as prebiotics. We also present studies that revealed synergistic effects of the co-administration of AA with probiotic bacteria, indicating that AA can be used to design novel symbiotics. Finally, we discuss the difficulty to bring free AA to the distal gut microbiota and we propose potential solutions such as the use of delivery systems including encapsulation to bypass absorption in the small intestine. Future studies will need to further identify individual AA, dose and mode of administration to optimize prebiotic effects for the benefit of human and animal health.

The Effect of Amino Acids on Production of SCFA and bCFA by Members of the Porcine Colonic Microbiota

Functional amino acids supplementation to farm animals is considered to not only be beneficial by regulating intestinal barrier, oxidative stress, and immunity, but potentially also by impacting the gut microbiota. The impact of amino acids on a piglet-derived colonic microbiota was evaluated using a 48-h in vitro batch incubation strategy. The combination of 16S rRNA gene profiling with flow cytometry demonstrated that specific microbial taxa were involved in the fermentation of each of the amino acids resulting in the production of specific metabolites. Branched chain amino acids (leucine, isoleucine, valine) strongly increased branched-chain fatty acids (+23.0 mM) and valerate levels (+3.0 mM), coincided with a marked increase of Peptostreptococcaceae. Further, glutamine and glutamate specifically stimulated acetate (~20 mM) and butyrate (~10 mM) production, relating to a stimulation of a range of families containing known butyrate-producing species (Ruminococcaceae, Oscillospiraceae, and Christensenellaceae). Finally, while tryptophan was only fermented to a minor extent, arginine and lysine specifically increased propionate levels (~2 mM), likely produced by Muribaculaceae members. Overall, amino acids were thus shown to be selectively utilized by microbes originating from the porcine colonic microbiota, resulting in the production of health-related short-chain fatty acids, thus confirming the prebiotic potential of specific functional amino acids.

Oxidation of amino acids, glucose, and fatty acids as metabolic fuels in enterocytes of developing pigs

Enterocytes of young pigs are known to use glutamine, glutamate, and glucose as major metabolic fuels. However, little is known about the roles of aspartate, alanine, and fatty acids as energy sources for these cells. Therefore, this study simultaneously determined the oxidation of the amino acids and glucose as well as short- and long-chain fatty acids in enterocytes of developing pigs. Jejunal enterocytes were isolated from 0-, 7-, 14- and 21-day-old piglets, and incubated at 37 °C for 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing 5 mM D-glucose and one of the following: D-[U-¹⁴C]glucose, 0.5-5 mM L-[U-¹⁴C]glutamate, 0.5-5 mM L-[U-¹⁴C]glutamine, 0.5-5 mM L-[U-¹⁴C]aspartate, 0.5-5 mM L-[U-¹⁴C]alanine, 0.5-2 mM L-[U-¹⁴C]palmitate, 0.5-5 mM [U-¹⁴C]propionate, and 0.5-5 mM [1-¹⁴C]butyrate. At the end of the incubation, ¹⁴CO₂ produced from each ¹⁴C-labeled substrate was collected. Rates of oxidation of each substrate by enterocytes from all age groups of piglets increased (P < 0.05) gradually with increasing its extracellular concentrations. The rates of oxidation of glutamate, glutamine, aspartate, and glucose by enterocytes from 0- to 21-day-old pigs and of alanine from newborn pigs were much greater (P < 0.05) than those for the same concentrations of palmitate, propionate, and butyrate. Compared with 0-day-old pigs, the rates of oxidation of glutamate, aspartate, glutamine, alanine, and glucose by enterocytes from 21-day-old pigs decreased (P < 0.05) markedly, without changes in palmitate oxidation. Oxidation of alanine, propionate, butyrate and palmitate by enterocytes of pigs was limited during their postnatal growth. At each postnatal age, the oxidation of glutamate, glutamine, aspartate, and glucose produced much more ATP than alanine, propionate, butyrate and palmitate. The degradation of glutamate was initiated primarily by glutamate-pyruvate and glutamate-oxaloacetate transaminases. Our results indicated that amino acids (glutamate plus glutamine plus aspartate) are the major metabolic fuels in enterocytes of 0- to 21-day-old pigs.