Dietary Protein Digestion Research Articles

WHOLE GRAIN OF DIFFERENT CORN HYBRIDS IN THE FINISHING DIET OF LAMBS

The objective of this study was to compare whole grains of different corn hybrids in the finishing diet of lambs in terms of apparent digestibility, ingestive behavior and feedlot performance. Twenty-four crossbred lambs housed in individual pens were used. The animals were fed 7.35% hay and 92.65% concentrate (dry matter basis) containing 23.05% of a protein supplement plus 69.6% whole corn grains of the hybrids P3862, P4285 or Status for 72 days and were then slaughtered. The final body weight (40.82 kg) or daily weight gain (251 g) did not differ between lambs fed the different hybrids. Daily dry matter intake, expressed as percentage of live weight, was lower in the group fed the Status hybrid and intermediate in the group fed the P3862 hybrid. The Status hybrid resulted in lower digestibility of dietary crude protein, dry matter, and organic matter. There was no difference in hot carcass weight (19.8 kg), hot carcass yield (48.6%) or ingestive behavior between animals fed the different hybrids. Whole grains of the corn hybrids P3862 and P4285 are more indicated for fattening lambs fed with high-concentrate diets.

SLC15 family of peptide transporters (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The Solute Carrier 15 (SLC15) family of peptide transporters, alias H+-coupled oligopeptide cotransporter family, is a group of membrane transporters known for their key role in the cellular uptake of di- and tripeptides (di/tripeptides). Of its members, SLC15A1 (PEPT1) chiefly mediates intestinal absorption of luminal di/tripeptides from overall dietary protein digestion, SLC15A2 (PEPT2) mainly allows renal tubular reuptake of di/tripeptides from ultrafiltration and brain-to-blood efflux of di/tripeptides in the choroid plexus, SLC15A3 (PHT2) and SLC15A4 (PHT1) interact with both di/tripeptides and histidine, e.g. in certain immune cells, and SLC15A5 has unknown physiological function. In addition, the SLC15 family of peptide transporters variably interacts with a very large number of peptidomimetics and peptide-like drugs. It is conceivable, based on the currently acknowledged structural and functional differences, to divide the SLC15 family of peptide transporters into two subfamilies.

Biofloc technology (BFT): Adjusting the levels of digestible protein and digestible energy in diets of Nile tilapia juveniles raised in brackish water

Several studies have been performed adjusting the levels of dietary digestible protein and digestible energy for tilapia, but none of them was performed in biofloc technology (BFT) system, especially in brackish (10) water. In this sense, three levels of digestible protein (22, 26 and 30% DP) and three levels of digestible energy (3000, 3150 and 3300 kcal DE / kg) were evaluated on growth performance, body composition, hematological parameters and planktonic community in juveniles of Nile tilapia (O. niloticus) raised under BFT conditions. A total of 540 tilapia fingerlings (GIFT strain with 1.25 ± 0.15 g initial weight) were reared during 42 days in thirty-six plastic tanks (75 L), fed three times a day. No interaction was detected in the parameters evaluated. The fish fed with feed containing 26% and 30% of DP obtained higher final weight, specific growth rate and condition factor as compared to those fed with 22% of DP (P < 0.05). Body protein on tilapia carcass increased proportionally according to dietary protein. The higher dietary energy level promoted a higher body lipid deposition. According to hematological parameters fish from all treatments presented a satisfactory immunological status. The monitoring of planktonic community indicated a variation over time, specially on the number of dinoflagellates, rotifers and microalgae. The results indicated that diets containing 26% of DP and 3150 kcal / kg of DE for Nile tilapia juveniles promoted suitable growth performance and health conditions when reared in biofloc brackish water, and enabled savings in regards to dietary protein once the energy levels were adjusted.

Effects of phytonutrients on growth performance, antioxidative status, and energy utilization of broilers fed low energy diets.

Two experiments were conducted to investigate the effects of phytonutrients (PN) on growth performance, antioxidant status, intestinal morphology, and nutrient utilization of birds fed low energy diets. In Exp. 1, a total of 1,440 one-day-old Ross 308 male broiler chickens were randomly divided into 3 treatment groups, with 16 replicates per treatment (48 pens; 30 birds per pen). Birds in treatment 1 were fed diets with normal energy content (NE). Birds in treatment 2 were fed NE diet but with 60 kcal removed (LE). Birds in treatment 3 were assigned to LE diet supplemented with PN (LE + PN). Results indicated that LE diet increased feed conversion ratio (FCR) compared with NE from d 1 to 38, while LE + PN diet prevented this response (P = 0.02). At d 26, birds in the LE + PN group had the highest ileal and jejunal villus height to crypt depth (VH:CD) ratio. At d 39, PN supplementation improved ileal and jejunal VH:CD ratio, compared with LE group. Moreover, birds fed PN diets received a better economic profit. In Exp. 2, 360 one-day-old Ross 308 male broiler chickens were used in a metabolism study. The treatments used in Exp. 2 were the same as those in Exp.1, with 4 replicates (pens) and 30 birds in each replicate. Dietary apparent metabolism energy (AME), energy and protein digestibility were determined between 21 and 28 d of age. Results showed that chickens fed LE + PN diet tended to have greater AME (P = 0.02) and nitrogen-corrected apparent metabolism energy (AMEn) (P = 0.03) than birds fed LE diets. It was concluded that LE + PN showed a potential advantage to improve feed conversion and gut health of broilers, as well as economic profits.

Digestive enzymes and parasitology of Nile tilapia juveniles raised in brackish biofloc water and fed with different digestible protein and digestible energy levels

Biofloc technology (BFT) system is increasing around the world and Nile tilapia is suggested as the major fish species for such technology. The objective of this study was to evaluate diets with different levels of digestible protein (22, 26 and 30% DP) and digestible energy (3000, 3150 and 3300 kcal kg−1) for Nile tilapia juveniles raised in brackish biofloc system water (10 ppt) and its effects on the activity of digestive enzymes and the presence of ectoparasites in the gills. Tilapia juveniles (1.25 ± 0.15 g of initial weight) were stocked in thirty-two experimental units (100 L tanks) with 15 fish per tank. After 42 days fish were harvested, sampled and analyzed. The pepsine (stomach) and trypsine (intestine) activities significantly increased according to the increase of dietary levels. For both cases the higher activity was observed in 30% DP treatment (P < 0.05), with (pepsine) and without interaction (trypsine) with digestible energy levels. The opposite trend was observed for chymotripsine activity (intestine), in which 22% DP presented the higher activity, with significant interaction with energy levels. The higher activity for intestinal lipase activity was observed in 3150 kcal kg−1. No difference was found for ectoparasite analyses in gills between the treatments. Although in all treatments monogea type was found (70–90% of prevalence), the number of parasites per fish was low in all treatments (<1.6 parasites fish−1). The results suggested that differences in dietary digestible protein and digestible energy affected the activity of digestive enzymes in Nile tilapia juveniles raised in biofloc with 10 ppt of salinity. On the other hand, biofloc system did not promote ectoparasite spread even with low dietary levels of digestible protein and digestible energy.

Influence of Probiotics on Dietary Protein Digestion and Utilization in the Gastrointestinal Tract.

Protein is essential to growth and metabolism. Many factors influence dietary protein digestion and utilization in the gastrointestinal tract. Probiotics have attracted increasing attention in recent years owing to their broad health benefits, which may include a positive influence on the digestion and utilization of proteins. Several observations support their potential role in protein digestion. For example, probiotics can regulate the intestinal microflora and thereby influence intestinal bacteria related to proteolysis. Probiotics can also induce host digestive protease and peptidase activity, and some can release exoenzymes involved in the digestion of proteins. In addition, probiotics can improve the absorption of small peptides and amino acids by improving the absorption ability of the epithelium and enhancing transport. Furthermore, probiotics can reduce harmful protein fermentation and thus decrease the toxicity of metabolites. In this review, the roles of probiotics in intestinal protein digestion and utilization and the potential mechanisms underlying these effects are discussed.

Dietary Protein and Gut Microbiota Composition and Function.

Dietary protein and its metabolites, amino acids, are essential nutrients for humans and animals. Accumulated research has revealed that the gut microbiota mediate the crosstalk between protein metabolism and host immune response. Gut microbes are involved in the digestion, absorption, metabolism and transformation process of dietary protein in the gastrointestinal tract. Amino acids can be metabolized into numerous microbial metabolites, and these metabolites participate in various physiological functions related to host health and diseases. The components of dietary protein impact the gut microbiota composition and microbial metabolites. The source, concentration, and amino acid balance of dietary protein are primary factors which contribute to the composition, structure and function of gut microbes. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended over a diet with protein in excess of requirements. Greater levels and undigested protein lead to an increase of pathogenic microorganism with associated higher risk of metabolic diseases. Herein, the crosstalk between dietary protein and gut microbiota composition and function is summarized, which will help to reveal the potential mechanism of gut microbes on the gastrointestinal tract health.

Intestinal Signaling of Proteins and Digestion-Derived Products Relevant to Satiety.

Luminal nutrients stimulate enteroendocrine cells through the activation of specific receptors to release hormones that inhibit appetite and promote glucose homeostasis. While food protein is the macronutrient with the highest effect on satiety, the signaling on the protein digestion products at the gut is poorly understood. This perspective aims to highlight the existing gaps in the study of protein digestion products as signaling molecules in gastrointestinal enteroendocrine cells. Because dietary protein digestion can be modulated by the technological processes applied to food, it is possible to target gut receptors to control food intake by formulating specific food ingredients or protein preloads.

Pelleted total mixed ration improves growth performance of fattening lambs

Twenty-four fattening lambs were randomly assigned to two groups (completely randomized design) to assess effects of feeding a pelleted total mixed ration (PTMR) on growth performance and rumen fermentation characteristic of lambs. Dietary treatments were PTMR and unpelleted total mixed ration (UPTMR). During a 56-d fattening period, growth and digestibility were measured and samples of blood and rumen fluid were collected. At the end of the fattening period, lambs were slaughtered and digestive tracts were collected and evaluated. Dietary PTMR increased dry matter intake and average daily gain (P < 0.001) of lambs, but did not significantly affect feed conversion rate, increased apparent digestibility of dietary crude protein (P < 0.001), ash-free acid detergent fiber (P < 0.001), ether extract (P < 0.01), and starch (P < 0.001), but did not change apparent digestibility of dietary dry matter and amylase-treated ash-free neutral detergent fiber. Feeding PTMR increased concentrations of high density lipoprotein cholesterol (P < 0.05) and decreased low density lipoprotein cholesterol in plasma (P < 0.05) and hence was beneficial to health of lambs by modulating cholesterol metabolism. Feeding PTMR altered rumen fermentation and increased the ratio of acetate to propionate in rumen fluid (P<0.001). Furthermore, PTMR increased rumen papilla height and density (P < 0.001), decreased crypt depth of duodenum (P < 0.05) and hence increased the ratio of villus length to crypt depth and mucosal layer thickness of duodenum (P < 0.001), jejunum (P < 0.01), and ileum (P < 0.01). In conclusion, feeding PTMR increased growth performance of fattening lambs; this was attributed to improvements in gastrointestinal tract development, rumen fermentation characteristics and cholesterol metabolism.

Total and available tryptophan requirement of Nile tilapia,Oreochromis niloticus, fingerlings

The dietary total and available requirement of tryptophan of Nile tilapia fingerlings was determined using linear regression analysis. Six hundred fish (3.4 ± 0.0 g) were fed diets containing 296.4 g/kg of crude protein and 14.1 MJ/kg of digestible energy. Five extruded diets containing 2.5, 3.0, 3.4, 3.8 and 4.2 g/kg of total tryptophan were evaluated. Fish were fed four times a day during 45 days. Final body weight, weight gain, feed intake, feed conversion ratio and net protein utilization of fish fed Trp 3.4 and Trp 3.8 diets were improved compared to fish fed Trp 2.5 and Trp 4.2 diets. No significant differences in survival rate, whole‐body moisture and ash were observed. Whole‐body amino acid profile of fish fed different diets did not differ statistically (p > .05). Fish fed Trp 3.0 and Trp 3.4 diets showed higher tryptophan retention compared to fish fed Trp 2.5 and Trp 4.2 diets. Excepting blood glucose, no effects of dietary tryptophan on haematological parameters were observed. The dietary total tryptophan requirement of Nile tilapia fingerlings based on weight gain was estimated to be 3.4 g/kg (11.0 g/kg of dietary crude protein) or 3.0 g/kg of available tryptophan (11.0 g/kg of dietary digestible protein).

Dietary Amino Acid Availability and Anabolic Signaling Molecule Phosphorylation is Blunted in Maintenance Hemodialysis Patients

Skeletal muscle mass loss is a common feature in patients with renal failure receiving maintenance hemodialysis (MHD) therapy. Dietary protein (amino acids) is one of the main anabolic stimuli to skeletal muscle tissue in humans, and impairments to anabolic stimuli over time may lead to muscle mass loss. However, there are major gaps in our knowledge of how muscle mass is regulated by protein intake in MHD patients. PURPOSE: To compare dietary protein digestion and absorption kinetics and phosphorylation of anabolic signaling proteins after mixed meal ingestion in MHD patients and age- and BMI-matched controls. METHODS: 8 MHD patients (age: 56±5 y; BMI: 32±2 kg/m2) and 8 controls (age: 50±2 y; BMI: 31±1 kg/m2) received primed continuous infusions of L-[1-13C]leucine and ingested a mixed meal (546 kcal, 20 g protein, 59 g carbohydrate, 26 g fat) with protein provided as intrinsically L-[5,5,5-2H ]leucine labeled eggs. Breath, blood, and muscle biopsies were collected to determine amino acid concentrations, leucine enrichments, and phosphorylation of mTORC1 on Ser2448 during a 5 postprandial period. RESULTS: Postprandial release of dietary leucine into circulation over 5 h was reduced in MHD patients (41±5%) vs. controls (61±4%; P=0.03). The feeding-mediated increase in mTORC1 phosphorylation was blunted in MHD patients (0.6-fold above basal) vs. controls (1.1-fold above basal; P=0.006) at 5 h of the postprandial period. CONCLUSION: Our data demonstrated impaired kinetics of digestion/absorption of dietary proteins and reduced postprandial plasma amino acid availability in circulation after mixed meal ingestion in MHD patients when compared to age- and BMI-matched controls. This diminished dietary amino acid availability may have partly contributed to the blunted anabolic signaling mechanisms in MHD patients. Supported by the Egg Nutrition Center (ENC)

Effects of macro-nutrient, micro-nutrient composition and cooking conditions on in vitro digestibility of meat and aquatic dietary proteins

Animal and aquatic meats represent important sources of dietary protein and micro-nutrients. Although red and processed meats carry some risks for human health, sensory and nutritional advantages drive meat consumption. Therefore, it is important to understand how meat processing and cooking influence healthiness. The research aim was to investigate relationships of meat composition (proximates, amino acids and minerals) and cooking conditions (raw, 90 s microwave, 200 °C oven for 10 or 30 min) on protein digestibility, for a selection of four animal (beef, chicken, pork, kangaroo) and four aquatic meats (salmon, trout, prawn, oyster). Lean meats were minced before cooking followed by in vitro gastro-intestinal digestion and analysed for progress of hydrolysis, and size ranges of peptides using MALDI-TOF-MS. Correlation matrix analysis between compositional and functional parameters indicated that digestibility was significantly linked with protein and metal concentrations, likely reflecting moisture-dependent solubility and inter-mixing of sarcoplasmic metallo-proteins and insoluble myofibrillar proteins.

Fast digestive proteins and sarcopenia of aging.

The speed of dietary protein digestion influences postprandial amino acid availability which is crucial for improving altered anabolic response of skeletal muscle one feature of sarcopenia during aging. By analogy with carbohydrate and in reference to their absorption rate, dietary proteins can be classified as 'fast' or 'slow' proteins depending on matrix food structure and technological processes, which can influence amino acids availability and their subsequent metabolic actions. 'Fast' digestive proteins have been shown to stimulate muscle protein synthesis and to improve muscle function in several recent studies involving older patients. These new aspects may be applied for improving health through preservation or restoration of muscle protein mass and function in clinical situations (obesity, rheumatoid arthritis and cancer cachexia). Using fast digestive proteins is of major interest to overcome 'anabolic resistance' of aging for limiting sarcopenia. Fast proteins' action on muscle anabolism may be stimulated by other nutrients like vitamin D or omega 3 fatty acids or by combination with exercise. The beneficial impact of the 'fast' protein concept beyond the amount of dietary protein on muscle preservation is a promising therapeutic perspective to improve mobility and quality of life of older patients affected with chronic disease.

Graded levels of a defatted green microalgae inclusion in diets for broiler chicks led to moderate up-regulation of protein synthesis pathway in the muscle and liver

This experiment was to determine effects of graded levels of defatted green microalgal biomass (DGA, Nannochloropsis oceanica) on dietary protein digestion, retention, and metabolism, and on regulations of protein synthesis and energy partitioning in broiler chickens. One-day old broiler chicks were fed a corn-soybean meal-based diet containing 0 (control), 2, 4, 8 or 16% DGA for 6weeks (n=6cages/diet, 6chicks/cage). Graded levels of dietary DGA did not affect plasma and muscle protein and(or) plasma uric acid concentrations. Additionally, DGA consumption did not affect dry matter and nitrogen digestibility or retention, nor daily nitrogen excretion, as measured by both an ingestible marker and a 3-day total excreta collection. The inclusion of 4 to 8% of DGA produced moderate elevations (0.06<P<0.1) in the protein amounts (mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E (eIF4E)) or the phosphorylation (S6 ribosomal protein) of key regulators for the protein synthesis pathway in the breast muscle. The 8% DGA diet elevated (P<0.05) the protein amounts of hepatic S6 kinase and acetyl-CoA carboxylate compared with the control diet. Dietary DGA inclusion did not cause consistent changes of the energy partitioning checkpoint regulator adenosine monophosphate-activated protein kinase (AMPK) protein expression in either the breast muscle or liver. In conclusion, DGA at moderate levels of inclusion in the diets for broilers showed similar digestibility and retention of nitrogen to corn and soybean meal, with a moderate potential in stimulating the protein synthesis pathway in the muscle and liver.

Relative influence of dietary protein and energy contents on lysine requirements and voluntary feed intake of rainbow trout fry.

The effect of dietary digestible protein (DP) and/or digestible energy (DE) levels on lysine (Lys) requirements, Lys utilisation efficiency and voluntary feed intake (VFI) were studied in rainbow trout fry when Lys was the first limiting indispensable amino acid or in excess in the diet. Two trials were conducted at 11·6°C with eighty-one experimental diets, containing 280 g DP/kg DM (low protein (LP), trial 1), 600 g DP/kg DM (high protein (HP), trial 1) or 440 g DP/kg DM (medium protein (MP), trial 2), 17 MJ DE/kg (low energy (LE)), 19·5 MJ DE/kg (medium energy (ME)) or 22 MJ DE/kg (high energy (HE)), and nine Lys levels from deeply deficient to large excess (2·3-36 g/kg DM). Each diet was given to apparent satiety to one group of fifty fry (initial body weight 0·85 g) for 24 (MP diets, trial 2) or 30 (LP and HP diets, trial 1) feeding days. Based on N gain data fitted with the broken-line model, the relative Lys requirement was significantly different with the dietary DP level, from 13·3-15·7 to 22·9-26·5 g/kg DM for LP and HP diets, respectively, but did not significantly change with the DE level for a same protein level. The Lys utilisation efficiency for protein growth above maintenance was constant across diets, suggesting no effect of either dietary DE or DP levels. In Lys excess, the VFI was markedly decreased by the DP level but not by the extra DE supply. Our results suggest that the relative Lys need is best expressed in terms of percentage of protein content for optimum fish feed formulation, at least in rainbow trout fry.

Inactivation Methods of Trypsin Inhibitor in Legumes: A Review.

Seed legumes have played a major role as a crop worldwide, being cultivated on about 12% to 15% of Earth's arable land; nevertheless, their use is limited by, among other things, the presence of several antinutritional factors (ANFs- naturally occurring metabolites that the plant produces to protect itself from pest attacks.) Trypsin inhibitors (TIs) are one of the most relevant ANFs because they reduce digestion and absorption of dietary proteins. Several methods have been developed in order to inactivate TIs, and of these, thermal treatments are the most commonly used. They cause loss of nutrients, affect functional properties, and require high amounts of energy. Given the above, new processes have emerged to improve the nutritional quality of legumes while trying to solve the problems caused by the use of thermal treatments. This review examines and discusses the methods developed by researchers to inactivate TI present in legumes and their effects over nutritional and functional properties.

Protein Ingestion before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial

Background: The loss of skeletal muscle mass with aging has been attributed to the blunted anabolic response to protein intake. Presleep protein ingestion has been suggested as an effective strategy to compensate for such anabolic resistance.Objective: We assessed the efficacy of presleep protein ingestion on dietary protein digestion and absorption kinetics and overnight muscle protein synthesis rates in older men.Methods: In a randomized, double-blind, parallel design, 48 older men (mean ± SEM age: 72 ± 1 y) ingested 40 g casein (PRO40), 20 g casein (PRO20), 20 g casein plus 1.5 g leucine (PRO20+LEU), or a placebo before sleep. Ingestion of intrinsically l-[1-13C]-phenylalanine- and l-[1-13C]-leucine-labeled protein was combined with intravenous l-[ring-2H5]-phenylalanine and l-[1-13C]-leucine infusions during sleep. Muscle and blood samples were collected throughout overnight sleep.Results: Exogenous phenylalanine appearance rates increased after protein ingestion, but to a greater extent in PRO40 than in PRO20 and PRO20+LEU (P < 0.05). Overnight myofibrillar protein synthesis rates (based on l-[ring-2H5]-phenylalanine) were 0.033% ± 0.002%/h, 0.037% ± 0.003%/h, 0.039% ± 0.002%/h, and 0.044% ± 0.003%/h in placebo, PRO20, PRO20+LEU, and PRO40, respectively, and were higher in PRO40 than in placebo (P = 0.02). Observations were similar based on l-[1-13C]-leucine tracer (placebo: 0.047% ± 0.004%/h and PRO40: 0.058% ± 0.003%/h, P = 0.08). More protein-derived amino acids (l-[1-13C]-phenylalanine) were incorporated into myofibrillar protein in PRO40 than in PRO20 (0.033 ± 0.002 and 0.019 ± 0.002 MPE, respectively, P < 0.001) and tended to be higher than in PRO20+LEU (0.025 ± 0.002 MPE, P = 0.06).Conclusions: Protein ingested before sleep is properly digested and absorbed throughout the night, providing precursors for myofibrillar protein synthesis during sleep in healthy older men. Ingestion of 40 g protein before sleep increases myofibrillar protein synthesis rates during overnight sleep. These findings provide the scientific basis for a novel nutritional strategy to support muscle mass preservation in aging and disease. This trial was registered at www.trialregister.nl as NTR3885.

The effect of varying dietary digestible protein and digestible non-protein energy sources on growth, nutrient utilization efficiencies and body composition of carp (Cyprinus carpio) evaluated with a two-factorial central composite study design

The effect of varying dietary digestible protein and digestible non-protein energy sources on growth, nutrient utilization efficiencies and body composition of carp (<i>Cyprinus carpio</i>) evaluated with a two-factorial central composite study design

Double-Stranded RNA-Mediated Suppression of Trypsin-Like Serine Protease (t-SP) Triggers Over-Expression of Another t-SP Isoform in Helicoverpa armigera.

High diversity of digestive proteases is considered to be the key factor in the evolution of polyphagy in Helicoverpa armigera. Serine proteases (SPs) contribute ~85% of the dietary protein digestion in H. armigera. We investigated the dynamics of SP regulation in the polyphagous pest, H. armigera using RNA interference (RNAi). HaTry1, an isoform of SP, expressed irrespective of the composition of the diet, and its expression levels were directly proportional to the larval growth rate. Therefore, HaTry1 was silenced by delivering 10 and 20μg concentrations of double-stranded RNA through semi-synthetic diet. This led to a drastic reduction in the target gene transcript levels that manifested in a significant reduction in the larval weight initially, but the larvae recovered in later stages despite continuous dsRNA treatment. This was probably due to the compensatory effect by over-expression of HaTry13 (31-folds), another isoform of SP. Phylogenetic analysis of H. armigera SPs revealed that the over-expressed isoform was closely related to the target gene as compared to the other tested isoforms. Further, silencing of both the isoforms (HaTry1 and HaTry13) caused the highest reduction in the larval weight and there was no larval growth recovery. These findings provide a new evidence of the existence of compensatory effect to overcome the effect of silencing individual gene with RNAi. Hence, the study emphasizes the need for simultaneous silencing of multiple isoforms.

Digestible Protein Requirement of Pirarucu Juveniles (Arapaima gigas) Reared in Outdoor Aquaculture

Pirarucu (Arapaima gigas) is a fast-growing, carnivorous species reared commercially in Amazonian countries as Brazil. Lack of a nutritionally balanced and affordable diet is a major constraint in pirarucu aquaculture, and our investigation sought to estimate the dietary protein requirement for this species. Four diets were formulated to contain increasing concentrations of digestible protein (32, 35, 38, and 41%) and fed to triplicate groups of juvenile pirarucu of around 2 kg for 18 weeks. As result, pirarucu showed no differences in feed intake, survival, or fillet yield. However, regression analysis revealed that weight gain (WG) values showed a general increasing trend with increasing dietary digestible protein (DP) level up to 36.7%. In addition, feed conversion rates were also improved with increase in dietary DP up to 36.4%. Fish fed diets containing 32 and 41% had poor feed conversion rates. Thel protein retention rate (PRR) and protein efficiency index (PER) decreased as levels of DP increased. The optimal dietary protein content for juvenile pirarucu between 1.98 and 4 kg of BW is about 36% of digestible protein on diet.