Dietary Taurine Level Research Articles

Evaluation of the dietary taurine requirement for early juvenile mud crab Scylla paramamosain

As a conditionally essential amino acid (CEAA), taurine plays an important role in the growth, development, and physiological metabolism of aquatic animals; however, its demand level in the mud crab Scylla paramamosain is still poorly understood. A 60-day growth trial was conducted to investigate the effects of different taurine levels (0% (T0.0), 0.2% (T0.2), 0.4% (T0.4), 0.8% (T0.8), and 1.6% (T1.6)) added to diet on the survival, growth, body composition, immunity, antioxidant and osmoregulatory capacity of early juvenile S. paramamosain (initial body weight 8.69 ± 0.19 mg). The results showed that dietary taurine levels >0.4% (inclusive) significantly increased the survival of early juvenile mud crabs. The growth performance (final body weight (FBW), weight gain (WG), specific growth rate (SGR)) of early juvenile mud crabs increased significantly with increasing dietary taurine levels, reaching a maximum in the T0.8 group, and the target of rapamycin (tor) gene transcription levels also peaked in the T0.8 group. The body composition of mud crabs was not affected by dietary treatments. Further, dietary taurine significantly increased digestive enzyme (trypsin, lipase, and amylase) activities and transcript levels of appetite-related genes (neuropeptide F1 (npf1) and neuropeptide F2 (npf2)) in early juvenile mud crabs. In addition, dietary taurine increased the expression levels of immune-related genes (prophenoloxidase (proPO), prophenoloxidase activating factor 1 (ppaf1), prophenoloxidase activating factor 2 (ppaf2), crustin antimicrobial peptide (crustin), lysozyme (lzm)) and antioxidant capacity (total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and catalase (CAT) activities) in early juvenile mud crabs. Finally, the results of the acute salinity challenge showed that the early juvenile mud crabs' survival in the T0.8 group was significantly higher than that of the other groups, while significantly higher Na+/K+-ATPase (NKA) activity and Na+/K+-ATPase α-subunit (nka-α) and Na+/K+/2Cl−-cotransporter (nkcc) gene expression levels were also detected in the T0.8 group. Together with growth performance, immunity, antioxidant capacity and osmoregulatory capacity, the present study concluded that the appropriate dietary taurine level for early juvenile mud crabs was 1.08%–1.33%.

Transcriptome-based nutrigenomics analysis reveals the roles of dietary taurine in the muscle growth of juvenile turbot (Scophthalmus maximus)

The present study explored transcriptomics and gene regulation variations in the muscle of turbot fed with dietary taurine. A 70-day feeding trial was conducted using turbot (initial body weight: 3.66 ± 0.02 g) fed with different levels of dietary taurine: 0 % (C), 0.4 % (T2), 1.2 % (T4) and 2.0 % (T6). Two methods were used to analyze and verify the taurine effects on muscle growth: (1) real-time quantitative PCR (qRT-PCR) for the key muscle growth-related genes and (2) transcriptomic analysis by next-generation sequencing (NGS). The results showed that 1.2 % of dietary taurine supplementation significantly increased the expression of muscle growth stimulatory genes, including TauT, myoD, Myf5, myogenin and follistatin. And also, the 1.2 % level significantly decreased the expression of the muscle growth-restricting gene (myostatin). Meanwhile, transcriptomics analysis found that 1.2 % dietary taurine supplementation significantly increased the number of up-regulated genes linked to metabolic pathways. In contrast, taurine significantly enriched the actin cytoskeleton and metabolic pathways in the T4 and T2 groups, respectively. These findings align with the gene ontology (GO) analysis, which indicated a higher number of cellular component (CC) gene expressions at a 1.2 % of dietary taurine compared to a 0.4 % of dietary taurine supplementation. In conclusion, dietary taurine had positive impacts on the growth-stimulatory genes. Moreover, 1.2 % of dietary taurine supplementation is important to the metabolic pathway enrichment.

Implications on growth performance, glucose metabolism, PI3K/AKT pathway, intestinal flora induced by dietary taurine in a high-carbohydrate diet for grass carp (Ctenopharyngodon idella).

An 8-week experiment was performed to investigate the influence on growth performance, plasma biochemistry, glucose metabolism and the insulin pathway of supplementation of dietary taurine to a high-carbohydrate diet for grass carp. In this study, fish were fed diets at one of two carbohydrate levels, 31·49 % (positive control) or 38·61 % (T00). The high-carbohydrate basal diet (T00), without taurine, was supplemented with 0·05 % (T05), 0·10 % (T10), 0·15 % (T15) or 0·20 % (T20) taurine, resulting in six isonitrogenous (30·37 %) and isolipidic (2·37 %) experimental diets. The experimental results showed that optimal taurine level improved significantly weight gain, specific growth rate (SGR), feed utilisation, reduced plasma total cholesterol levels, TAG and promoted insulin-like growth factor level. Glucokinase, pyruvate kinase and phosphoenolpyruvate carboxykinase activities showed a quadratic function model with increasing dietary taurine level, while hexokinase, fatty acid synthetase activities exhibited a positive linear trend. Optimal taurine supplementation in high-carbohydrate diet upregulated insulin receptor (Ir), insulin receptor substrate (Irs1), phosphatidylinositol 3-kinase (pi3k), protein kinase B (akt1), glycogen synthase kinase 3 β (gs3kβ) mRNA level and downregulated insulin-like growth factor (igf-1), insulin-like growth factor 1 receptor (igf-1R) and Fork head transcription factor 1 (foxo1) mRNA level. The above results suggested that optimal taurine level could improve growth performance, hepatic capacity for glycolipid metabolism and insulin sensitivity, thus enhancing the utilisation of carbohydrates in grass carp. Based on SGR, dietary optimal tributyrin taurine supplementation in grass carp was estimated to be 0·08 %.

Effects of exogenous taurine supplementation on the growth, antioxidant capacity, intestine immunity, and resistance against Streptococcus agalactiae in juvenile golden pompano (Trachinotus ovatus) fed with a low-fishmeal diet.

Taurine has various biological functions in fish, playing an essential role in growth, resistance to oxidative stress, and intestine immunity. Here, we evaluated the effects of exogenous taurine added to low-fishmeal diets on the growth, anti-oxidative stress, intestine immunity, and Streptococcus agalactiae resistance in juvenile golden pompano (Trachinotus ovatus). Our study showed that exogenous taurine supplementation of 1.2% (T3 group) greatly enhanced the weight gain rate and specific growth rate (SGR) of juvenile golden pompano, significantly upregulating growth-related factor expression in the brain and liver, as well as the levels of growth-related parameters in the serum. Polynomial regression analysis using SGR estimated the optimal dietary taurine level for golden pompano at 1.18%. Moderate exogenous taurine also increased the muscular thickness and villus length within the intestine, maintained intestinal physical barrier stability, activated the Nrf2/Keap-1/HO-1 signaling pathway, increased intestinal antioxidant enzyme gene expression and antioxidant enzyme activity in the serum, and upregulated immunoglobulin and complement levels in parallel with declining reactive oxygen species (ROS) levels in the serum. Antioxidant factor expression was also upregulated in the intestine. Furthermore, supplementation suppressed NF-κB signaling and intestinal pro-inflammatory cytokine gene expression, increased anti-inflammatory cytokine gene expression, and improved intestine immunity. Finally, taurine supplementation improved the survival rate of golden pompano challenged with S. agalactiae. Overall, our findings provide additional information and support for the rational use of taurine in healthy aquatic animal farming.

Effect of Amino Acid Taurine on Grass Carp Ctenopharyngodon idella Fingerlings during Salinity Stress

The present study was carried out to evaluate the effect of different levels of dietary taurine (0%, 1%, 2% and 3%) on grass carp Ctenopharyngodon idella fingerlings during salinity stress. Fishes (1.73-8.57 g) were fed a diet up to satiation twice daily for ten weeks in four treatments: T1, T2, T3 and T4. At the end of the feeding trial, fishes were stressed by exposure to 10 PSU salinity for 14 days during which fish survival rates, total protein, glucose, oxygen and energy consumption were observed. The results showed that there were no significant differences (P>0.5) in the survival rates between treatments, which ranged from 73.3% to 93.3%. Total protein and glucose were significantly (P≤0.05) improved by a dietary taurine diet after 14 days of salinity stress in T2 and T3. Taurine supplementation significantly (P≤ 0.05) influenced oxygen consumption with the highest value observed for T1 (255.8 mg O2/kg/hr) and T2 (213.6 mg O2/kg/hr), while the lowest value was in T3 (131.5 mg O2/kg/hr) and T4 (112.4 mg O2/kg/hr) after 14 days of salinity stress. Energy consumption rates were significant (P≤0.05) different between the treatments on the 14th day, T1 (0.85 kcal/kg/hr) significantly exceeded the other treatments, followed by T2 (0.72 kcal/kg/hr), T3 (0.44 kcal/kg/hr) and T4 (0.38 kcal/kg/hr). It appeared that taurine could be used as a feed supplement to confirm better energy consumption and blood biochemical parameters during salinity exposure of grass carp fingerlings with the optimal level of a 2% and 3% diet.

The optimal dietary taurine supplementation in zero fish meal diet of juvenile snakehead fish (Channa striata)

The most common alternative protein sources are plant-based proteins such as soybean meal but one of the limitations is taurine deficiency that can be especially detrimental for carnivorous fish. This study was to determine the important roles of dietary taurine on the growth performance, feed utilization and body composition of juvenile snakehead fish with an initial weight of 4.66–4.71 g/fish. Five test diets were investigated, using various taurine supplementation levels and both isonitrogenous and isoenergetic formulas: 1)control (fish meal inclusion); 2)zero fish meal diet (ZF) without taurine supplementation (T0); 3) ZF with taurine supplementation at 0.5% (T0.5); 4) ZF with taurine supplementation at 1.0% (T1.0); 5) ZF with taurine supplementation at 1.5% (T1.5). Fish were fed with five different dietary taurine levels for 60 days. Weight gain (WG), average daily gain (ADG) and specific growth rate (SGR) were higher in the control group of fish, followed by the T0.5 and T1.0 group but the lowest level was observed in fish fed the T0 and T1.5 (p < 0.05). The statistical results of Survival rate (SR), feed conversion ratio (FCR) and protein efficiency ratio (PER) were not significantly different (p > 0.05) among all experimental groups, whereas fish fed diet T0.5 and T1.0 had good trend in FCR and PER value similar to the control group. Dietary taurine might not affect on whole-body composition in juvenile snakehead fish (p > 0.0). Taurine accumulation in fish whole body and the liver both showed the increasing trends varying supplementation levels in each experimental diet. In the current study, taurine supplementation had no observable effects on the histological structures of liver and distal intestines of snakehead fish. This phenomenon indicated that the taurine supplementation at 0.5% in the plant protein-based diet (ZF) cloud be improved the growth performance and feed utilization of juvenile snakehead fish. Leading to, this is a positive sign of a possibility to reduce feed cost by completely taking fish meal out of a future commercial aquafeed for better aquaculture business sustainability.

Growth performance, biochemical composition and expression of lipid metabolism related genes in groupers ( Epinephelus coioides ) are altered by dietary taurine

Six experimental diets containing 100 and 150 g/kg lipid, and 0, 10, and 20 g/kg taurine in a 2 × 3 factorial design were fed to triplicate groups of 30 grouper Epinephelus coioides with an initial weight of 10.5 ± 0.1 g to apparent satiation twice daily for eight weeks. Fish fed diets with 150 g/kg lipid showed an increase in lipid contents of whole-body, muscle and liver, and plasma levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), apolipoprotein B and leptin, but a decrease in whole-body moisture, ash and protein contents, and a down-regulation of mRNA levels of acc, fas and pparα genes in the liver vs fish fed with 100 g/kg lipid, regardless of dietary taurine level. Increasing dietary taurine resulted in an increase in percent weight gain and feed efficiency, whole-body protein and muscle lipid contents, plasma levels of total bile acid and HDL-C, as well as hepatic levels of 3-hydroxy-3-methy1 glutary1 coenzyme A reductase and cholesterol 7 alpha hydroxylase, but a decrease in hepatosomatic index and liver lipid content, plasma levels of TC, LDL-C, apolipoprotein B, and insulin-like growth factor vs taurine-free diets. Furthermore, dietary taurine addition down-regulated the mRNA levels of g6pd and l-fabp genes, and up-regulated the mRNA levels of pparα gene in the liver vs taurine-free diets. The results showed an effect of reducing lipid accumulation of taurine when fish fed the diets with taurine increased from zero to 10 g/kg or fed the 10 g/kg taurine diets with lipid increased from 100 to 150 g/kg. The growth promotion and lipid-lowering effects of taurine are closely associated with the changes of plasma lipid components and hepatic metabolic enzyme activities, as well as the regulation of gene expression of liver lipid metabolism related enzymes of groupers.

An evaluation on taurine addition in the diet of juvenile sea cucumber ( Apostichopus japonicus ): Growth, biochemical profiles and immunity genes expression

A 60-day feeding trial was conducted to evaluate the effects of dietary taurine (Tau) levels on the growth, biochemical profiles and related immune gene expression of sea cucumbers (Apostichopus japonicus). A total of 225 sea cucumbers (initial body weights 0.79 ± 0.05 g) were randomly stocked into 5 groups (three tanks per group) and received one of the following diets: Each diet was supplemented with 0 g/kg (T0), 5 g/kg (T0.1), 10 g/kg (T0.5), 20 g/kg (T1) or 50 g/kg (T2) Tau. The sea cucumber weight gain rate, specific growth rate, feed efficiency and crude protein content increased in Tau-supplemented groups compared with T0 group. The body wall total amino acids and total essential amino acids in Tau-supplemented groups were significantly lower than in T0 group while the Tau contents were significantly higher. The acid phosphatase, alkaline phosphatase and complement 3 values were significantly increased in T0.5/T1. Meanwhile, total superoxide dismutase activities in T0.1, T0.5 and T1 were significantly higher than T0 group. The intestinal ATP synthase, Aj-p105, Aj-lys and AjTRX gene expression levels were significantly increased in Tau supplementation groups than in T0 group. And Tau optimum content in the diet of juvenile sea cucumber was determined as 3 g/kg of the dry diet.

Growth, serum biochemical parameters, salinity tolerance and antioxidant enzyme activity of rainbow trout (Oncorhynchus mykiss) in response to dietary taurine levels.

This study evaluated the effect of dietary taurine levels on growth, serum biochemical parameters, salinity adaptability, and antioxidant activity of rainbow trout (Oncorhynchus mykiss). Four diets were formulated with taurine supplements at 0, 0.5, 1, and 2% w/v (abbreviated as T0, T0.5, T1, and T2, respectively). Rainbow trouts (initial weight of 80.09 ± 4.72g) were stocked in tanks (180 L capacity), and were fed these diets for six weeks and subsequently underwent salinity acclimation. Physiological indicators were determined before salinity acclimation at 1, 4, 7, and 14days afterwards. Results showed that there were no significant differences in growth performance (final mean weight ranged from 182.35g to 198.48g; percent weight gain was between 127.68% and 147.92%) of rainbow trout in freshwater stage, but dietary taurine supplement significantly increased serum-free taurine content. After entering seawater, the Na+-K+-ATPase activity of T2 group returned to its freshwater levels, and the serum cortisol content was significantly higher than T0 and T0.5 groups. At the end of this experiment, the liver superoxide dismutase activity in the T0 and T0.5 groups was significantly lower than in the T1 and T2 groups, and the liver catalase in the T0 group was the lowest whereas that in the T2 group was the highest. Muscle malondialdehyde content was the highest in the T0 group, and the lowest in the T2 group. Based on the results of this study, supplement of dietary taurine (0.5-2%) enhanced the salinity tolerance in rainbow trout, which increased with the higher taurine concentration.

Evaluating the dietary taurine requirement of hybrid striped bass, (Morone chrysops x M. saxatilis)

A dietary requirement for the sulfonic acid taurine has been documented in many marine species. However, it has not been well studied in hybrid fish with freshwater and marine genes, such as the hybrid striped bass (Morone chrysops x M. saxatilis). Therefore, an 8-week feeding trial was conducted to evaluate the effects of various levels of dietary taurine on growth performance, health, and body composition of juvenile hybrid striped bass. Four diets were formulated from practical ingredients and supplemented with DL-methionine at 0.54% of dry weight to meet the hybrid striped bass' established total sulfur amino acid requirement of 1.0% of dry diet, and taurine was supplemented incrementally at 0, 0.5, 1, and 2% of dry weight. Two additional diets were prepared without DL-methionine supplementation to be marginally deficient in methionine (0.49% by weight) and either supplemented with or without taurine at 1% dry weight to evaluate the potential interactions between methionine and taurine. Diets containing increment levels of taurine were determined to show no significant (P > .05) differences in terms of weight gain, feed efficiency (FE), whole-body composition, hepatosomatic index (HSI), intraperitoneal fat ratio (IPF ratio), or muscle yield. However, hybrid striped bass fed the methionine-deficient diets had significantly (P < .05) reduced percentage weight gain and FE as well as reduced muscle yield and HSI compared to fish fed the methionine-supplemented diets. Interestingly, taurine inclusion at 1% in the diet containing 0.49% methionine increased weight gain and feed efficiency of fish compared to those fed the diet without supplemental taurine or methionine. These results indicated that growth performance and body composition of hybrid striped bass did not respond to taurine supplementation when dietary methionine was adequate but did respond when dietary methionine was limiting.

Dietary taurine improves vision in different age gilthead sea bream (Sparus aurata) larvae potentially contributing to increased prey hunting success and growth

The effect of different levels of dietary taurine on vision, prey hunting success and growth was tested in developing larval gilthead sea bream (GSB; Sparus aurata). Fifteen 17 L aquaria were stocked with 3000 fertilized eggs aquarium−1 from a local GSB broodstock, which allowed the testing of 5 prey taurine treatments in triplicate aquaria treatment−1. Nine aquaria tested the effect of the non-taurine enriched rotifer (Brachionus rotundiformis) control (1.7 mg g−1 DW) and two taurine enriched rotifer treatments (6.6 and 11.0 mg g−1 DW) in 2 to 13 dph larvae followed by feeding non-taurine enriched Artemia nauplii (36.6 mg g−1 DW) to all treatments from 14 to 31 dph. Larvae in another 6 aquaria were fed control rotifers (1.7 mg g−1 DW) from 2 to 13 dph followed by testing the effect of taurine enriched Artemia nauplii (51.5 and 61.9 mg g−1 DW) on 16 to 31 dph larvae. In parallel, GSB fertilized eggs from the same broodstock were stocked (100 eggs L−1) in fifteen 400 L conical, polypropylene tanks, which tested the 5 rotifer and Artemia taurine levels in triplicate tanks treatment−1. Only rotifer consumption (mastax number) in 7 and 13 dph larvae and dry weight of 31 dph larvae were determined in the aquaria, while total length, essential fatty acid profile, taurine level, opsin abundance and gene expression of selected opsin genes in different age larvae were determined from the much larger biomass of the 400 L tanks.The growth of 3 and 13 dph larvae were significantly (P < 0.05) correlated with rotifer and larval body taurine levels in a dose-dependent manner. Moreover, rotifer ingestion (mastax number) significantly (P < 0.05) improved in 13 dph larvae with rotifer taurine level. The growth promoting effect of rotifer taurine continued to significantly (P < 0.05) influence larval length in older 21and 26 dph larvae, although this effect diminished (P > 0.05) in 31dph larvae. The contribution of taurine to improved vision was supported in 31 dph larvae, which exhibited significantly (P < 0.05) increasing retinal opsin protein abundance with rotifer taurine level in a dose dependent manner. In fact, dietary taurine markedly (P < 0.05) improved the gene expression of 5 different opsins in 8 and 31 dph larvae. Nevertheless, the correlation between rotifer taurine and larval fatty acid content suggests that the taurine-modulated production of bile salts facilitated lipid digestion and absorption, which also might have promoted growth.

Dietary taurine intake affects growth and taurine synthesis regulation in golden pompano, Trachinotus ovatus (Linnaeus 1758)

Taurine serves an important role in many species, including fish. The purpose of this study was to investigate the effects of varying dietary taurine levels on the growth, antioxidant capacity, and tissue deposition of taurine in golden pompano. In addition, the mechanism of taurine synthesis was studied via enzyme activity and gene expression of the following enzymes: cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), cysteine dioxygenase (CDO), cysteine sulfinic acid decarboxylase (CSAD), and 2-aminoethanethiol dioxygenase (ADO). Taurine concentrations of 1.3, 4.4, 7.4, 10.5 and 12.7 g kg−1 were added to the basic feed, hereafter labelled the T0, T1, T2, T3 and T4 diets, respectively. A control diet was supplemented with 1.3 g kg−1 taurine. Following 8 weeks of treatment, the results showed that the specific growth rate increased with the increase in dietary taurine content; the growth rate peaked at the 10.5 g kg−1 dietary taurine level (P < 0.05). The hepatosomatic index was significantly reduced as dietary taurine levels increased (P < 0.05). Crude protein and crude lipid in the body increased significantly with the intake of exogenous taurine (P < 0.05). The increase in dietary taurine significantly increased the total antioxidant capacity, as well as the superoxide dismutase, catalase, and glutathione peroxidase activities; however, the malondialdehyde concentration correspondingly decreased (P < 0.05). The taurine content in whole fish, liver, heart, eye, kidney, brain, muscle and gill significantly increased with the increase in dietary taurine (P < 0.05). The activity of CSE, CDO, CSAD and ADO decreased with the increase in dietary taurine (P < 0.05). Taurine intake had no significant impact on CBS activity (P > 0.05). The gene expression of CBS, CSE, CDO, CSAD and ADO exhibited a downward trend with an increase of taurine (P < 0.05). These results indicate that taurine plays an important role in the growth of golden pompano. Polynomial regression analysis revealed that the taurine requirements of golden pompano could be satisfied if the taurine content reached at least 10.0 g kg−1. In addition, taurine has a regulating effect on taurine synthesis in golden pompano.

Dietary taurine incorporation to high plant protein-based diets improved growth, biochemical, immunity, and antioxidants biomarkers of African catfish, Clarias gariepinus (B.).

Plant protein (PP) sources are generally used in high levels in fish diets. Mostly, PP sources are deficient in taurine; hence, there is a need for its supplementation to fish fed high PP diets. Therefore, effects of dietary taurine were examined on growth performance, feed utilization, immunity, and antioxidant parameters of African catfish, Clarias gariepinus (B.). Fish (10.3 ± 0.4g) were fed on diets (40% crude protein) containing different taurine levels of 0 (control), 10, 20, 30, or 40g/kg diet for 12weeks. Fish fed a taurine-free diet (the control) with high PP sources showed poor growth as compared with these fed taurine-enriched diets where taurine stimulatory effects were observed on fish growth and feed intake. Feed conversion ratio and fish survival rate were not significantly differed among different treatments. Fish fed taurine-enriched diets showed also higher levels of serum glucose, cholesterol, total protein, albumin, globulin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, urea, and creatinine over that fed the control diet. Furthermore, lysozyme and respiratory burst activities as well assuperoxide dismutase and catalase activities were significantly elevated in fish fed taurine-enriched diets (P < 0.05) and their highest levels were observed in fish fed 30g/kg diet. Additionally, taurine deposition in fish muscles was positively correlated with dietary taurine levels (P < 0.05). The present study concludes that taurine is a limiting factor for growth, immunity, and antioxidants responses of African catfish fed high PP-based diets and it should be incorporated in its diets with an optimum level of 20g/kg diet.

Taurine supplementation in high-soy diets affects fillet quality of European sea bass (Dicentrarchus labrax)

This study evaluated the effects of taurine supplementation to diets containing a high dietary inclusion of soybean meal and soy protein concentrate on growth performance and fillet quality of juvenile European sea bass (Dicentrarchus labrax). A control diet (C+) was produced containing high levels of fishmeal (30% FM) and soybean meal (20% SBM). Three other experimental diets were prepared to contain a lower FM inclusion (25%), and a higher amount of soy products (20% of SBM plus 12% soy protein concentrate, SPC) supplemented with three graded levels of crystalline taurine, 0.2%, 0.5% and 1.0% (T0.2, T0.5 and T1.0), respectively. A fifth diet was also prepared having a similar composition as the latter three diets but without the addition of crystalline taurine (negative control diet, C-). All diets were iso-nitrogenous (44%), iso-lipidic (20%) and iso-energetic (22 ​MJ ​kg−1) and were fed to five triplicate groups of sea bass (initial weight 86 g) over the course of a 12-week trial. Dietary taurine supplementation did not affect the growth performance and feed efficiency (P > 0.05). Proximate composition of whole body and muscle were similar among groups (P > 0.05). Taurine dietary supplementation had no effect on the level of intraperitoneal fat deposition (P > 0.05). However, muscle taurine concentration was found to increase gradually in sea bass fed the elevated levels of taurine (P < 0.05). Interestingly, the hardness and chewiness of the fillet, recorded by texture analysis, increased significantly at higher dietary taurine levels (P < 0.05). The highest adhesiveness values were obtained in sea bass fed the C- diet, whereas the lowest ones were found in fish fed the T1.0 diet (P < 0.05). No significant (P > 0.05) impact of diets on texture fillet springiness and cohesiveness was found (P > 0.05). In general, no significant differences were observed by the test panel, however, fish fed the diet supplemented with 1.0% taurine exhibited lower fillet elasticity, thus indicating a potential textural difference in accordance with those obtained from the texture analysis of fish muscles. The histological analysis did not indicate any differences in the gut and liver of the fish fed the experimental diets. Overall, the findings of the present study showed that 1.0% taurine supplementation in diets incorporating high levels of soy products might have a pronounced effect on flesh quality of European sea bass.

Effects of dietary taurine level on visual function in European sea bass (Dicentrarchus labrax).

Dietary insufficiencies have been well documented to decrease growth rates and survival (and therefore overall production) in fish aquaculture. By contrast, the effects of dietary insufficiencies on the sensory biology of cultured fish remains largely unstudied. Diets based solely on plant protein sources could have advantages over fish-based diets because of the cost and ecological effects of the latter, but plant proteins lack the amino acid taurine. Adequate levels of taurine are, however, necessary for the development of a fully functional visual system in mammals. As part of ongoing studies to determine the suitability of plant-based diets, we investigated the effects of normal and reduced taurine dietary levels on retinal anatomy and function in European sea bass (Dicentrarchus labrax). We could not demonstrate any effects of dietary taurine level on retinal anatomy, nor the functional properties of luminous sensitivity and temporal resolution (measured as flicker fusion frequency). We did, however, find an effect on spectral sensitivity. The peak of spectral sensitivity of individuals fed a 5% taurine diet was rightward shifted (i.e., towards longer wavelengths) relative to that of fish fed a 0% or 1.5% taurine diet. This difference in in spectral sensitivity was due to a relatively lower level of middle wavelength pigment (maximum absorbance .500 nm) in fish fed a 5% taurine diet. Changes in spectral sensitivity resulting from diets containing different taurine levels are unlikely to be detrimental to fish destined for market, but could be in fishes that are being reared for stock enhancement programs.

Molecular characterization and taurine regulation of two novel CDOs (CDO1 and CDO2) from Carassius auratus.

Cysteine oxygenase (CDO) is a mononuclear nonhemoglobin enzyme that catalyzes the production of taurine through the cysteine (Cys) pathway and plays a key role in the biosynthesis of taurine in mammals. However, the function of CDOs in bony fish remains poorly understood. In this study, we cloned CDO genes (CaCDO1 and CaCDO2) from Carassius auratus. The cDNA sequences of both CaCDO1 and CaCDO2 encoded putative proteins with 201 amino acids, which included structural features typical of the CDO protein family. Multiple sequence alignment and phylogenetic analysis showed that CaCDO1 and CaCDO2 shared high sequence identities and similarities with C. carpio homologs. Quantitative real-time polymerase chain reaction (qRT-PCR) results revealed that CaCDO1 and CaCDO2 were both broadly expressed in all selected tissues and developmental stages in C. auratus but had differing mRNA levels. In addition, compared to those of the taurine-free group, the in vivo mRNA expression levels of both CaCDO1 and CaCDO2 significantly decreased with increasing dietary taurine levels from 1.0 to 9.0 g/kg. Furthermore, in vitro taurine treatments showed similar inhibitory effects on the expression of CaCDO1 and CaCDO2 in the intestines of C. auratus. Our results also showed that the mRNA expression of CaCDO2 in the intestines was higher than that of CaCDO1 in response to in vivo and in vitro taurine supplementation. Overall, these data may provide new insights into the regulation of fish CDO expression and provide valuable knowledge for improving dietary formulas in aquaculture.

Synergistic effects of dietary carbohydrate and taurine on growth performance, digestive enzyme activities and glucose metabolism in juvenile turbot Scophthalmus maximus L.

A 10-week feeding trial was conducted to evaluate the effects of taurine on growth performance, digestive enzyme activities and glucose metabolism of juvenile turbot Scophthalmus maximus (initial body weight, 3.66 ± 0.02 g) fed diets with different carbohydrate level. With a 2 × 3 two factoral experimental design, two levels of dietary carbohydrate (15% and 21%, respectively) with three levels of taurine (0.4%, 1.2%, and 2.0%, respectively) were used. In addition, the diet with 15% carbohydrate and without taurine supplementation was used as the control. The results showed that, compared with the control group, 1.2% of dietary taurine supplementation significantly increased the specific growth rate, the activities of amylase and lipase in intestine, glycogen content and the mRNA levels of glucokinase, phosphofructokinase, pyruvate kinase, glucose-6-phosphate dehydrogenase (G6PD), glycogen synthase (GS) and glucose transporter 2 in liver at 15% of dietary carbohydrate level. Meanwhile, it significantly decreased the blood glucose concentration and the mRNA levels of cytosolic phosphoenolpyruvate carboxykinase (cPEPCK) in liver. In addition, significant interaction between dietary carbohydrate and taurine were observed in blood glucose level. Compared to 15% dietary carbohydrate, 21% dietary carbohydrate significantly increased the blood glucose level at 1.2% and 2.0% dietary taurine level, whereas it had no significant effect at 0.4% dietary taurine supplementation level. At 21% of dietary carbohydrate level, although 1.2% and 2.0% of dietary taurine supplementation had no significant effects on blood glucose level, it significantly decreased the advanced glycationend products level in plasma and the fructose-1, 6-bisphosphatase mRNA level in liver. Moreover, compared to that fed diet with 15% carbohydrate, fish fed diet with 21% carbohydrate had lower activities of amylase and lipase in intestine and lower mRNA levels of G6PD, mitochondrial phosphoenolpyruvate carboxykinase and cPEPCK in liver. Furthermore, significant interactions between dietary carbohydrate and taurine were also observed in the expression of the genes involved in liver glucose metabolism above in addition to GS and cPEPCK. Overall, this study indicated that taurine had a beneficial effect on glucose homeostasis through enhancement of glycolysis, glucose transport, glycogen synthesis and the inhibition of gluconeogenesis in liver of turbot, thus decreased blood glucose level. However, the beneficial effect of taurine on glucose metabolism was affected by dietary carbohydrate level.

Effect of dietary taurine supplementation on growth performance, digestive enzyme activities and antioxidant status of juvenile black carp (Mylopharyngodon piceus ) fed with low fish meal diet

An 8-week feeding trial was conducted to determine the effects of dietary taurine supplementation on growth performance, activities of digestive enzymes, antioxidant status and the target of rapamycin (TOR) gene expression in black carp (initial body weight 5.94 ± 0.02 g) fed with low fish meal diet. Six isonitrogen and isolipidic diets were formulated. High fish meal–based diet (HFM) contained 20% fish meal and 24% soybean meal as a positive control. Fifty per cent of fish meal in HFM was replaced by soybean meal and were supplemented with 0, 0.05%, 0.1%, 0.2% and 0.4% dietary taurine respectively (designated as T0.00 (a negative control), T0.05, T0.1, T0.2 and T0.4). The results showed that the partial replacement of fish meal by soybean meal without taurine supplementation resulted in a significant reduction in weight gain (WG), activities of amylase and lipase in intestine, superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) in serum, with a significant increase in feed conversion rate (FCR), the content of malonaldehyde (MDA), triglyceride (TG) and total cholesterol (TC) in serum. WG in groups supplemented with equal or above to 0.1% dietary taurine was significantly higher compared with T0 group. With increasing levels of dietary taurine, the activities of amylase, lipase, GSH-px and SOD and glutataione (GSH) content significantly increased (p < 0.05). FCR, the content of MDA, TG and TC in serum and crude lipid content in whole body were significantly reduced after taurine treatment (p < 0.05). In liver, TOR mRNA expression in groups with equal or above to 0.1% taurine was significantly higher than T0 group (p < 0.05).

Protective effects of taurine on growth performance and intestinal epithelial barrier function in weaned piglets challenged without or with lipopolysaccharide

We evaluated whether weaned piglets were protected from bacterial endotoxins by placing the animals on a taurine-supplemented diet. A total of 40 weaned Landrace × Yorkshire piglets (5.75 ± 0.58 kg, weaned at 21 days) were allocated to four groups with 10 barrows per group, following a 2 × 2 factorial design with two inclusion levels of lipopolysaccharide (LPS) (no or one time peritoneal injection by the dose of 100 µg/kg bodyweight on Day 7 of the trial) and two inclusion levels of dietary taurine (no or 0.1% taurine in a basal diet in the whole trial). There was a significant interaction between LPS and taurine with regard to growth and small intestinal mucosal membrane integrity, morphology, immune parameters, and antioxidant capacity (P &lt; 0.05). Feed conversion, daily weight gain, daily feed intake, villus height, and the villus to crypt ratio, vascular endothelial growth factor, regenerating islet-derived protein 3 gamma, trefoil factor-3, transforming growth factor β-1 expression, number of goblet cells and the least amount of claudin-1, occludin, zonula occludens-1, serum glutathione peroxidase, nitrogen oxide synthase, superoxide dismutase, peroxidase, and total antioxidant was lowest in LPS-challenged animals. Furthermore, animals in the LPS group had the highest serum diamine oxidase concentration, number of lymphocytes, concentrations of calprotectin, sIgA, toll-like receptor-4, mRNA levels of interleukin-1β, interleukin-8, toll-like receptor-4, and tumour necrosis factor-α (P &lt; 0.05). These data suggested that the peritoneal injection administration of LPS decreased growth performance and disrupted small intestinal mucosal membrane integrity and triggered an inflammatory response in the small intestinal mucosal membrane. Dietary administration of taurine improved growth performance, increased small intestinal villus height, stimulated immune and antioxidant function and improved small intestinal mucosal membrane integrity in weaned piglets challenged without or with LPS (P &lt; 0.05). The beneficial effects of taurine were likely due to decreased stimulation of the immune response to LPS and an improvement in intestinal epithelial barrier function. Dietary administration of taurine could prevent weaned piglets from intestinal damage by LPS of Gram-negative bacteria.

The effect of dietary taurine on growth performance and liver histopathology in Persian sturgeon,Acipenser persicus(Borodin, 1897) fed plant-based diet

This experiment was conducted to illustrate the effect of dietary taurine levels on Persian sturgeon, Acipenser persicus (mean weight of ~35 g) fed plant-based diet. A basal diet containing low level of fishmeal (19%) was formulated containing 0.05% endogenous taurine (control diet). To this diet were added five levels of exogenous taurine: 0.25 (0.25T), 0.5 (0.5T), 0.8 (0.8T), 1.2 (1.2T) and 1.6% (1.6T). These diets were fed to the experimental fish for 42 days. Results showed that growth performance decreased and food conversion ratio increased as dietary taurine increased, although no significant difference was observed between the control and 0.25T treatments. Increased dietary taurine led to increased carcass moisture and decreased carcass lipid percentages. Feed intake was significantly and negatively correlated with dietary taurine. Carcass taurine content significantly increased with dietary taurine elevation up to 1.2% and then decreased. Hepatic taurine content showed a significant increase in 0.25T treatment and then decreased along with dietary taurine elevation and reached the control values at 1.6% taurine level. Dietary taurine elevation led to more hepatic damages compared to the control. In conclusion, although within the range reported for other studied fish, the tested taurine levels in this study might be supra-optimal causing adverse effects in Persian sturgeon and further study with lower taurine levels is encouraged.