Protein Retention Efficiency Research Articles

Dietary Chlorella vulgaris supplementation modulates health, microbiota and the response to oxidative stress of Atlantic salmon

Microalgae are emerging as functional feed ingredients in aquaculture due to their immune-stimulating and stress-modulating properties. We investigated the potential of the microalgae Chlorella vulgaris as a feed supplement to improve the health and modulate microbiota and stress responses of Atlantic salmon. Triplicate groups of Atlantic salmon (~ 126 g) were reared in a recirculating aquaculture system (RAS) at 15 °C and received diets supplemented with 2% (CV2) or 14% (CV14) spray-dried C. vulgaris daily, 14% once weekly (CV14w), or a control diet (CD) for 8 weeks. Subsequently, all groups were exposed to an acute one-hour peracetic acid (CH3CO3H; PAA) treatment, a commonly used disinfectant in RAS. While CV14 increased feed conversion (FCR) significantly, feeding the diets CV2 and CV14w improved protein retention efficiency. CV14 significantly modulated beta-diversity in the intestinal digesta and mucosa, but this effect was already visible in fish fed CV2. Feeding CV14 and, to a lesser degree, CV2 increased the relative abundances of Paenarthrobacter and Trichococcus in the digesta and mucosa, which are able to metabolize complex carbohydrates. However, the same diets reduced the abundance of the lactic acid bacteria Lactobacillus and Weissella in the digesta and Floricoccus in the mucosa. Peracetic acid exposure induced systemic stress (increase in plasma glucose and cortisol) and a local immune response in the gill, with the most prominent upregulation of several immune- and stress-regulated genes (clra, cebpb, marco, tnfrsf14, ikba, c1ql2, drtp1) 18 h after exposure in fish fed the control diet. Fish receiving CV14 once a week showed a reduced transcriptional response to PAA exposure. Catalase protein abundance in the liver increased following exposure to PAA, while superoxide dismutase abundance in the gill and liver was increased in response to C. vulgaris inclusion before stress. Overall, the results highlight that a high (14%) inclusion rate of C. vulgaris in feed for Atlantic salmon impairs feed conversion and shifts the intestinal microbiota composition in digesta and mucosa. Weekly feeding of C. vulgaris proves a viable approach in improving protein retention and improving transcriptional resilience towards oxidative stress in increasingly intensive production systems. Thereby this study may motivate future studies on optimizing temporal feeding schedules for health-promoting aquafeeds.

Effects of the extrusion process on the physical properties of micro pellets and the growth performance of juvenile Nile tilapia

The present study aimed to evaluate the effect of different extrusion processes on the physical properties of micro pellets and how the alterations affect the growth performance of juvenile Nile tilapia. Four experimental diets were produced with the same formulation, but with different extrusion processes: CE: cold extrusion (18 ºC); HE: hot extrusion (100 ºC); D1: double extrusion, first a hot extrusion (100 ºC) of all the ingredients followed by cold extrusion (18 ºC); D2: double extrusion, first a hot extrusion (100 ºC) of the plant-based ingredients followed by mixing with the animal-based ingredients and milling, then cold extrusion (18 ºC). Juvenile tilapia (0.83 ± 0.01 g; 3.68 ± 0.19 cm) were distributed in 20 experimental units (60 L; n=5; 20 fish per unit) in a completely randomized design for four weeks. The micro pellets of the experimental HE diet presented a positive expansion rate (2.86 ± 0.45 %) and a lower bulk density (465.9 ± 3.45 g/L). The D1 and D2 micro pellets presented higher bulk density (671.0 ± 2.98 and 612.8 ± 4.99 g/L, respectively). All the micro pellets showed high durability (>95 %). The D2 micro pellets showed low water resistance (24.4 ± 3.51 %), resulting in a high leaching rate of nutrients (>68 %). The HE and D1 micro pellets showed a higher absorption rate in water (3.65 ± 0.29 and 3.66 ± 0.21 g water/g, respectively). The water solubility index of the micro pellets was not influenced by the different extrusion processes (P > 0.05), nor were survival and feed consumption. The fish fed with the HE diet showed greater weight gain (3.84 ± 0.44 g), and the lowest weight gain was in the fish fed with the CE diet (3.05 ± 0.39 g) (P < 0.05). Feed conversion was lower in fish fed the HE (1.06) and D1 (1.11) diets (P < 0.05). Fish fed the HE diet had the highest values for relative growth rate (9.08 ± 0.62 %/d), protein retention (30.6 ± 2.61 %) and protein efficiency (2.26 ± 0.22 %) (P < 0.05). Fish fed the CE diet had the lowest values for relative growth rate (7.82 ± 0.51 %/d), protein retention (21.4 ± 2.72 %) and protein efficiency (1.55 ± 0.23 %) (P < 0.05), though the values are in line with those in the literature. In conclusion, hot extrusion resulted in micro pellets with better physical properties and fish with higher growth performance. Double extrusion, first a hot extrusion of the plant-based ingredients followed by mixing with the animal-based ingredients and milling, then cold extrusion is not recommended due to high levels of nutrient leaching. Cold extrusion and double extrusion, first a hot extrusion of all the ingredients followed by cold extrusion processing can be considered for producing micro diets for juvenile tilapia, especially when less investment in the extrusion process is desired.

Effect of taurine on growth and immune response of Pacific white shrimp (Litopenaeus vannamei) cultured at different temperatures

Low temperature is a common challenge in the culture of Pacific white shrimp (Litopenaeus vannamei), and taurine is a potential nutrient that may improve its cold-resistance. This experiment aimed to investigate effects of dietary taurine on growth and immune response of Pacific white shrimp cultured at normal and cold temperatures. Six diets were supplemented with increasing levels of taurine (0, 0.2, 0.4, 0.6, 0.8 and 1.0%) and fed to shrimp (1.59 ± 0.03 g) reared at two water temperatures (28 °C and 20 °C) for 8 weeks. The results showed that compared with 28 °C, shrimp reared at 20 °C showed lower growth performance, feed utilization, apparent digestibility and total hemocyte count (THC) (P < 0.05), but higher content of serum glucose, intracellular reactive oxygen species (ROS) and Ca2+, malonaldehyde (MDA) and apoptosis rate (P < 0.05), indicating a higher risk of oxidative damage during low temperature stress. Interestingly, shrimp could cope with cold stress by changing hemocyte composition, increasing antioxidant enzyme activity and genes expression of apoptosis and autophagy. The effect of taurine was different at different temperatures. At 28 °C, taurine supplementation improved growth rate of shrimp by increasing digestive enzyme activities, digestion absorption rate and nutrient utilization. Based on the quadratic model of weight gain rate, feed efficiency, protein retention efficiency and the broken line model of apparent digestibility coefficients of protein, the amount of taurine required for shrimp reared at 28 °C was 0.57–0.60% of dry diet. At 20 °C, taurine increased the number of THC, granulocytes, semi-granulocytes, the activities of antioxidant enzymes such as superoxide dismutase and catalase, and decreased the content of ROS in the cells, which may enhance cold resistance of shrimp. Moreover, taurine supplementation down-regulated mRNA expression of cell apoptosis genes (cyt-c, caspase-9 and caspase-3) and up-regulated mRNA expression of cell autophagy genes (atg1, atg13, atg7 and lc3) (P < 0.05), which may help to maintain cell stability at 20 °C. The optimal requirement of taurine in shrimp reared at 20 °C was 0.56–0.66% of dry diet in this experiment based on THC and MDA content. In conclusion, our study suggests that appropriate taurine promotes growth and feed utilization at optimal temperature and enhances the stability of hemocyte at low temperature in white shrimp.

Quantification of dietary valine requirement of fingerling Channa punctatus (Bloch) based on growth, feed conversion efficiency, carcass composition, hematology, and antioxidant status

A 12-week experiment was performed to determine the valine requirement of Channa punctatus (5.32 ± 0.08 g) by feeding purified diets (450 g/kg CP, 14.73 KJ/g DE) with graded levels of valine to triplicate groups of fishes to apparent satiation containing seven valine concentrations (7.5, 10, 12.5, 15, 17.5, 20 and 22.5 g/kg diets). Absolute weight gain, specific growth rate, feed conversion ratio, protein retention efficiency, protein efficiency ratio, and RNA/DNA ratio improved (P < 0.05) with the increasing concentrations of valine up to 15 g/kg diet. Carcass protein and moisture content showed a positive trend with incremental valine levels up to 15 g/kg, whereas fat contents showed a reverse pattern. The highest hemoglobin, red blood corpuscle, and hematocrit were found at 15 g/kg of dietary valine. Total serum protein, superoxide dismutase, catalase, glutathione peroxidase, and lysozyme increased with the increase in valine up to 15 g/kg, whereas malondialdehyde, alanine aminotransferase, aspartate aminotransferase significantly decreased (P < 0.05). From the results of absolute weight gain, feed conversion ratio, protein efficiency ratio, and protein retention efficiency, the range of dietary valine requirement for C. punctatus is 15.9–17.2 g/kg diet.

Development of dynamic growth and body composition models for Nile Tilapia (Oreochromis niloticus): An exploratory approach to protein and energy metabolism

The aquaculture sector has been steadily growing and thus there is an increasing need to develop mathematical models that allow the estimation of production-related parameters. Prediction of fish growth, feed requirements and waste outputs, are essential in order to ensure the profitability and sustainability of the production activities. Bioenergetic models have been widely used to estimate growth based on energy budgets, but they have some limitations by not explicitly considering the mass-balance of the main macronutrients (e.g., protein). In turn, nutrient-based models are more explanatory, as they consider both energy and nutrient inputs, and estimate fish growth by simulating nutrient accumulation in the fish body. Although some bioenergetic and nutrient-base models for predicting Nile tilapia growth exist in the literature, their suitability is not entirely clear, since their development is often based on uncertain or suboptimal criteria (e.g., relying solely on calibration goodness-of-fit measures).In this work, Nile tilapia growth datasets covering a wide range of rearing conditions and feed compositions were collected from the scientific literature. An exploratory analysis of the collected data was performed to clarify the relationships between energy/protein intake and gain. In this analysis, a direct relationship was observed between digestible energy intake and energy gain, as well as between digestible protein intake and protein gain. Protein gain showed better efficiency than energy gain, even at higher intake levels and without clear evidence of a saturation effect. While digestible energy intake negatively affects energy retention efficiency, digestible protein intake does not significantly impact protein retention efficiency. Furthermore, while energy retention efficiency varies with fish body weight, the same effect was not observed for protein retention efficiency. Finally, though DP/DE ratio has no apparent effect on energy retention efficiency, it seems to negatively affect protein retention efficiency. Considering these observations, plausible growth models with different levels of complexity were developed and calibrated under a diverse set of assumptions. Additionally, two growth models already published for Nile tilapia were calibrated using the same datasets, and their performance was compared with the models developed in the present study. The exploratory analysis of the data suggests a direct relationship between digestible energy intake and energy gain, and between digestible protein intake and protein gain. Furthermore, fish body weight seems to affect the energy retention efficiency. The results of model evaluation showed that energy-protein flux models (EP models) have lower errors in predicting fish growth than pure bioenergetic models (MAPEbw ∼ 9% against ∼13%, respectively), showing the importance of considering protein intake when estimating Nile tilapia growth. Furthermore, assuming the fixed standard metabolic body weight exponents of 0.80 and 0.70 (for energy and protein, respectively), rather than estimating them from the data, seemingly improved the predictive ability of the models. This approach demonstrates the benefits of coupling bioenergetics with nutrient-based models to predict growth and body composition of Nile tilapia along time.

Dietary Effects of Lipid and Protein Levels on Growth, Feed Utilization, Lipid Metabolism, and Antioxidant Capacity of Triploid Rainbow Trout (Oncorhynchus mykiss).

This study investigated the dietary effects of lipid and protein levels on growth performance, feed utilization, body composition, lipid metabolism, and antioxidant capacity of triploid rainbow trout, Oncorhynchus mykiss. A 3 × 2 two-factor design was conducted with three crude lipid levels of 4%, 9%, and 14% (L4, L9, and L14) and two crude protein levels of 44%, 49% (P44, P49). Therefore, a total of six diets were prepared as P44/L4, P44/L9, P44/L14, P49/L4, P49/L9, and P49/L14. Triploid rainbow trout (initial body weight 65.0 ± 0.1 g) were fed one of the six diets for 80 days. The results showed that weight gain (WG), protein retention (PR), and protein efficiency rate (PER) significantly increased with increasing the dietary lipid level at the same crude protein level, while feed conversion ratio (FCR) and hepatosomatic index significantly decreased (P < 0.05). At the same lipid level, there was no difference in WG, FCR, PR, PER between 44% and 49% crude protein group (P > 0.05). The P49/L14 group had the highest WG (374.6%) and lowest FCR (1.25), while P44/L14 group had the highest PER (1.80) and PR (25.06%) with similar WG and FCR to P49/L14 group. The crude lipid contents in whole fish were significantly higher in the L14 group than those in the L4 and L9 groups (P < 0.05). Muscle n-3 PUFAs, n-6 PUFAs, and PUFAs levels were positively correlated with dietary lipid level, while n-6 PUFAs was negatively correlated with dietary protein level. Dietary protein, dietary lipid, and their interaction significantly affected hepatic malondialdehyde (MDA) content, aspartate aminotransferase, lipase (LPS), and fatty acid synthase (FAS) activities (P < 0.05). In both P44 and P49 groups, LPS and FAS activities increased with increasing the dietary lipid level. MDA content significantly decreased in the P44 group and increased in the P49 group with increasing the dietary lipid level (P < 0.05). As dietary protein level increased, serum total cholesterol level increased, while hepatic phosphoenolpyruvate carboxykinase activity decreased. With increasing the dietary lipid level, total superoxide dismutase, catalase, total nitric oxide synthase, and fructose-1,6-bisphosphatase activities showed an increasing trend, while the opposite was true for alanine aminotransferase activity. In conclusion, based on growth performance and feed utilization, dietary protein level of 44% and dietary lipid level of 14% (measured value, 43.71% and 13.62%) were suggested for young triploid rainbow trout.

Evaluate of Wheat Gluten as a Protein Alternative for Fish Meal and Soy Protein Concentrate in Red Spotted Grouper Epinephelus akaara.

The aim of this study was to evaluate the effects of wheat gluten as a substitute for fish meal (FM) and soy protein concentrate (SPC) in the low-fishmeal-based extruded diet in red spotted grouper Epinephelus akaara. Eight isonitrogenous (441-456 g kg-1) and isocaloric (21.5-22.0 MJ kg-1) diets were produced, including the control diet (R0), three diets with 33.3, 66.7, and 100% FM being replaced by a mixture of wheat gluten, wheat, and taurine (GWT) (RF1, RF2, RF3), three diets with 33.3, 66.7, and 100% SPC replaced by GWT (RS2, RS2, RS3) and one diet with 50% FM and 50% SPC replaced by GWT (RFS). Results showed that feed intake (FI), weight gain (WG), protein retention efficiency, and liver superoxide dismutase activity increased linearly, while feed conversion ratio (FCR) decreased linearly with the decrease of dietary FM. Additionally, FI, WG, and FCR significantly increased with decreasing dietary SPC. Overall, 100% FM or 61.2% SPC can be safely replaced by wheat gluten in the red-spotted grouper diet containing 20.0% FM and 21.4% SPC.

Digestible protein levels and metabolic responses in juvenile piapara (Megaleporinus obtusidens)

The piapara (Megaleporinus obtusidens) is an omnivorous fish with great market potential. However, little is known about its dietary requirements. This study aimed to determine the effects of dietary protein on growth and physiological indicators in piapara. Three hundred piapara juveniles (24.0 ± 1.3 g) were distributed in 20 tanks of 130-L (15 fish/tank) provided with continuous aeration and water. Five isoenergetic diets (14.0 MJ/kg) were formulated to contain increasing levels of digestible protein (21, 24, 27, 30, and 33% DP). After 77 days, weight gain and ammonia concentration in water were found to increase linearly with increasing digestible protein (DP) level (p&lt;0.05). Protein productive value (PPV) reached a maximum at 28.4% DP. No relationship was found between DP level and serum ammonia, liver alanine aminotransferase (ALT) activity, hepatosomatic index (HSI), liver glycogen (GL) or liver lipid (LL) content (p&gt;0.05). Mesenteric fat index (MFI) and liver malic enzyme (ME) activity followed a quadratic pattern (p&lt;0.05) and reached a maximum at 25.8% and 27.1% DP, respectively. Muscle lipid (ML) content decreased linearly with increasing DP level (p&lt;0.05), whereas liver glucose-6-phosphate dehydrogenase (G6PD) activity decreased linearly as DP level increased (p&lt;0.05). Results showed that a diet containing 28.4% PD provides better crude protein retention efficiency and reduces amino acid deamination in M. obtusidens. Low protein diets increased energy retention efficiency, whereas fish fed high protein diets had higher ammonia excretion.

Dietary phenylalanine requirement and tyrosine replacement value for phenylalanine for fingerling Channa punctatus based on growth parameters, hematology and antioxidant status

In this study, a 12 week feeding trial was conducted to estimate the phenylalanine requirement and the tyrosine replacement value for phenylalanine of fingerling Channa punctatus. In experiment I, six isoproteic (450g kg−1 CP) and isoenergetic (14.73 kJ g−1 DE) experimental diets were prepared with various phenylalanine concentrations (2.5, 5, 7.5, 10, 12.5, 15 g kg−1 diet) at a fixed tyrosine level (10 g kg−1). Absolute weight gain, specific growth rate, feed conversion ratio, protein and phenylalanine retention efficiency and RNA/DNA ratio improved with incremental phenylalanine levels up to 10 g kg−1 of the diet, beyond which declined significantly. Red blood corpuscles, hemoglobin and hematocrit increased significantly with increasing phenylalanine levels up to 10 g kg−1 diet. Total serum protein, catalase, superoxide dismutase and lysozyme were positively correlated with incremental phenylalanine levels up to 10 g kg−1 whereas aspartate aminotransferase and alanine aminotransferase activity showed opposite patterns. Based on quadratic regression analysis of AWG and PRE, phenylalanine requirement was determined to be 10.2 and 11.5 g kg−1 diet respectively. In experiment II, six diets containing graded levels of tyrosine (1.9, 3.5, 5.2, 7.1, 9.5, 11 g kg−1) containing a fixed level of phenylalanine (10.6 g kg−1) were fed to fish to find out the tyrosine replacement value for phenylalanine. Based on AWG and PRE the tyrosine replacement value for phenylalanine was determined to be 41.4% and 42.3% on weight basis or 37.7% and 38.6% on molar basis, and total aromatic amino acid requirement was determined to be 17.2 and 19.8 g kg−1 diet, respectively.

Data Mining Evidences Variabilities in Glucose and Lipid Metabolism among Fish Strains: A Case Study on Three Genotypes of Gibel Carp Fed by Different Carbohydrate Sources.

An 8-week feeding trial was conducted to evaluate the application of common carbohydrate sources, cornstarch (CS), wheat starch (WS), and wheat flour (WF), to different gibel carp genotypes, Dongting, CASIII, and CASV. The results of the growth and physical responses were analysed by data visualization and unsupervised machine learning. As revealed by a self-organizing map (SOM) and the cluster of growth and biochemical indicators, CASV had superior growth and feed utilization and better regulation of postprandial glucose, followed by CASIII, while Dongting showed a high level of plasma glucose with poor growth performance. CS, WS, and WF were differently utilized by the gibel carp, and WF was associated with greater zootechnical performance based on higher specific growth rate (SGR), feed efficiency (FE), protein retention efficiency (PRE), and lipid retention efficiency (LRE), induced hepatic lipogenesis, increased liver lipids, and enhanced muscle glycogen. Spearman's correlation analysis of the physiological responses indicated that plasma glucose had a significantly negative correlation with growth, feed utilization, glycogen storage, and plasma cholesterol level, and it was positively related to liver fat content in gibel carp. Transcriptional variabilities were observed: CASIII showed increased expression of pklr, which is involved in hepatic glycolysis, and pck and g6p, which are involved in gluconeogenesis. Interestingly, Dongting showed upregulation of genes involved in glycolysis and fatty acid oxidation in muscle. Furthermore, there were numerous interactions between carbohydrate sources and strains for growth, metabolites, and transcriptional control, confirming the existence of genetic polymorphisms in carbohydrate use in gibel carp. Globally, CASV showed relatively better growth and carbohydrate utilization, and wheat flour seemed to be more efficiently utilized by gibel carp.

Dietary Supplementation with Chromium DL-Methionine Enhances Growth Performance of African Catfish (Clarias gariepinus).

Sustainable aqua feeds have become an urgent necessity for future-oriented aquaculture sector development, and especially mineral supply could be limited when diets are being prepared with low amounts of animal-based sources. Since knowledge about the efficiency of organic trace mineral supplementation in different species of fish is limited, the effects of chromium DL-methionine in African catfish nutrition were evaluated. Four commercially based diets with increasing chromium DL-methionine supplementation (0, 0.2, 0.4, and 0.6 mg Cr kg-1) in the form of Availa-Cr 1000 were fed to African catfish (Clarias gariepinus B., 1822) in quadruplicate groups for 84 days. Growth performance parameters (final body weight, feed conversion ratio, specific growth rate, daily feed intake, protein efficiency ratio, and protein retention efficiency), biometric indices (mortality, hepatosomatic index, spleen somatic index, and hematocrit), and mineral retention efficiency were assessed at the end of the feeding trial. The specific growth rate was significantly increased in fish-fed diets with 0.2 mg Cr kg-1 and 0.4 mg Cr kg-1 supplementation in comparison with control and based on the second-degree polynomial regression analysis; supplementation with 0.33 mg Cr kg-1 was optimal in commercially based diets for African catfish. Chromium retention efficiency was reduced with increasing supplementation levels; however, the chromium content of the whole body was comparable to literature. The results suggest that organic chromium supplementation is a viable and safe supplement for diets to increase the growth performance of African catfish.

Dietary leucine requirement of fingerling Channa punctatus (Bloch) based on growth, feed conversion and leucine retention efficiency, hematological parameters, antioxidant and intestinal enzyme activities.

To find out the dietary leucine requirement of fingerling Channa punctatus (5.24 ± 0.07g), six purified experimental diets (45% CP and 14.73kJ/g DE) with various leucine concentrations (0.5, 1.0,1.5, 2.0, 2.5 and 3.0% diet) were fed to apparent satiation to triplicate groups for 12weeks (714/02/a/CPCSEA). Absolute weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, protein and leucine retention efficiency, and RNA/DNA ratio improved up to 2.0% leucine in the diet. Carcass protein and fat increased significantly with increasing leucine levels up to a 2.0% dry diet. Moisture content showed a reverse pattern. Red blood corpuscles hemoglobin and hematocrit increased with incremental levels of leucine up to 2.0% diet. Significant changes were also noted in serum total protein, superoxide dismutase, aspartate aminotransferase, alanine aminotransferase, and lysozyme activity. Serum protein, superoxide dismutase and lysozyme activity were positively correlated with increasing leucine levels up to 2.0% diet, whereas aspartate aminotransferase and alanine aminotransferase showed the opposite trend. Based on the quadratic regression analysis of absolute weight gain, specific growth rate, feed conversion ratio, protein, and leucine retention efficiency, inclusion of 2.0% leucine is recommended for optimum growth of fingerling C. punctatus.

Different responses of grass carp (Ctenopharyngodon idellus) and black carp (Mylopharngodon piceus) to low-protein diets and subsequent recovery

An 8-week growth trial was designed to evaluate the effects of low-protein diets and subsequent recovery on grass carp (Ctenopharyngodon idellus) and black carp (Mylopharngodon piceus) in order to compare the compensatory growth of the two species with different feeding habits. During the restricted period (weeks 1–4), grass carp were fed three kinds of isoenergetic and isolipid diets containing 32% (C, Control), 27% (LEP), and 22% (LP) protein individually, and black carp were fed diets containing 37% (C, Control), 32% (LEP) and 27% (LP) protein individually. In the recovery period (weeks 5–8), all fish were fed the control diets individually. The results showed that the protein restriction led to significantly lower feed conversion efficiency (FCE) and specific growth rate (SGR) for two species. In the recovery period, test group grass carp had similar protein retention efficiency (PRE) and FCE to the control group and had significantly lower final body weights (FBW), succinate dehydrogenase (SDH), significantly higher lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) than the control group. The test group black carp had significantly higher PRE and FCE than the control group, and the LEP group had similar FBW, LDH, AST, and alanine aminotransferase (ALT) to the control group and had significantly lower pyruvate kinase (PK) and SDH. The study reveals that grass carp increase gluconeogenesis and fail to increase feed utilization efficiency significantly, thus failing to obtain compensatory growth. Black carp decrease the carbohydrate catabolism and tricarboxylic acid (TCA) cycle, increase feed utilization efficiency significantly and get compensatory growth in the LEP group. Black carp have better compensatory growth capacity than grass carp, and the different capacities may be related to the different nutrient utilization strategies of the two species.

Effects of a Phytogenic Supplement Containing Olive By-Product and Green Tea Extracts on Growth Performance, Lipid Metabolism, and Hepatic Antioxidant Capacity in Largemouth Bass (Micropterus salmoides) Fed a High Soybean Meal Diet.

A 10-week growth trial was conducted to investigate the effects of a phytogenic feed additive (PFA) containing olive by-products and green tea extracts supplemented to a reduced fishmeal/high soybean meal diet on the growth performance, hepatic antioxidant capacity, lipid metabolism, and liver health of largemouth bass (Micropterus salmoides). Three experimental diets were tested: (1) a control high fishmeal (40%) and low soybean meal (15.57%) diet (named HFM), (2) a reduced fishmeal (30%) and high soybean meal (30.97%) diet (named HSB), and (3) a HSB diet supplemented with the PFA at 500 mg/kg (named HSB+P). Each diet was assigned to four replicate tanks, each containing 30 largemouth bass (initial body weight, IBW = 48.33 ± 0.01 g). The results showed that increasing the soybean meal content in the diet did not negatively affect growth performance, whereas supplementation with PFA significantly increased weight gain and specific growth rate of largemouth bass compared to both HFM and HSB groups. Reducing fishmeal and increasing soybean meal in the diet caused oxidative stress with a higher content of ROS in the liver. However, the hepatic antioxidant capacity was enhanced, with reduced ROS and increased GSH-Px levels in the HSB+P group. Moreover, the decrease of plasma TG, LDL-C, and LDL-C/TC, and downregulation of lipogenesis and cholesterol synthesis gene expression in liver, indicated that supplementation with the PFA improved fish lipid metabolism. Protein retention efficiency was also significantly increased in largemouth bass fed the diet with PFA supplementation, which regulated (enhanced) AKT-mTOR phosphorylation. These results clearly indicated that a PFA containing olive by-product and green tea extracts can positively improve growth performance, protein retention efficiency, antioxidant capacity, and lipid metabolism of largemouth bass fed a reduced fishmeal/high soybean meal diet.

Effect of xylanase and β-glucanase on growth performance, activity of digestive enzymes, digestibility, and microbiome diversity of juvenile Nile tilapia fed soybean meal and/or sorghum distillers dried grains with solubles-based diets

Recent studies have identified the advantage of supplementing exogenous enzymes targeting non-starch polysaccharides (NSPs) to surmount the problem caused by high-fiber plant-based diets containing distillers' dried grains with solubles (DDGS). This research investigated the effects of supplementing a blend of xylanase and β-glucanase (XB) in diets containing soybean meal (SBM) and/or sorghum distillers dried grains with solubles (DDGS) on growth performance, blood biochemical parameters, activity of digestive enzymes, apparent digestibility coefficients (ADCs) and microbiome of juvenile Nile tilapia, Oreochromis niloticus. Fish (n = 192; 12.09 ± 0.43 g) were randomly assigned in a 2 × 2 factorial design, and fed diets comprised of two main protein sources [SBM or SBM plus DDGS (SBM/DDGS)] either not supplemented (−XB) or supplemented with XB (+XB; 0.2 g kg−1 diet) with four replicates in each group and 12 fish per replicate. Liquid XB blend was top-sprayed onto extruded diets containing 17.6 MJ kg−1 gross energy and 313.6 g kg − 1 crude protein to provide 1120 TXU kg−1 of endo-1,4-β-xylanase and 500 TGU kg−1 diet of endo-1,4-β-glucanase. Fish were stocked into 70-L aquaria in a recirculating aquaculture system with a water flow of 0.5 L s−1 and temperature set at 28 °C throughout the trial. Fish were hand-fed six times daily until apparent satiety for 56 days. There was no interaction between protein source and XB, and fish fed the SBM diets had higher body weight gain, feed efficiency ratio, energy retention efficiency and protein retention efficiency compared to those fed SBM/DDGS diets. XB promoted higher body weight gain (+12.5%), feed efficiency ratio (+3.4%) and energy retention efficiency (+8.6%) aligned with increased activity of amylase (+32.0%) and lipase (+15.1%) enzymes in the gut than those fed the −XB diets. An interaction effect identified higher digestible energy (DE; +2.1 MJ kg−1 diet) contents in the SBM/DDGS diet with XB compared to the other diets. Analysis of the “core microbiota” revealed that Fusobacteria (Cetobacterium) dominated gut microbiota, irrespective of dietary treatment. Additionally, XB supplementation increased the bacterial diversity by quantifying operational taxonomic units (OTUs) regardless of the main dietary protein. Notably, fish fed the SBM/DDGS diets revealed a higher abundance of beneficial bacteria Proteobacter (Plesiomonas) and Firmicutes (Lactobacillus) than those fed diets of only SBM, irrespective of XB supplementation. Fish offered diet containing SBM/DDGS with XB had a higher abundance of Actinobacteria (Bifidocterium) than those fed other diets. Overall, this study found SBM to have higher nutritive value than DDGS, and supplementation of XB could alleviate the adverse effects of antinutritional factors in sorghum DDGS. Additionally, sorghum DDGS stimulated the abundance of beneficial bacteria in the gut microbiota.

Well‐defined multispecies probiotic and enzyme combination outperforms traditional fermented probiotic applications in an intensive Pacific white shrimp, Litopenaeus vannamei (Boone, 1931), culture system

AbstractA series of treatments were designed to evaluate the efficacy of feeding commercial multispecies probiotics feeding with enzymes and fermentation process on the growth parameters and culture environment of Pacific white shrimp, Litopenaeus vannamei (Boone, 1931), in an intensive culture system. Commercial multispecies probiotics and enzymes (PEs) were continuously applied in three different doses, namely (i) 0.2, (ii) 0.4, and (iii) 0.6 mg L−1 and designated as 0.2, 0.4, and 0.6 PE during the first 30 days of intensive culture of Pacific white shrimp, L. vannamei (Boone, 1931). The probiotics were continually applied every alternate day, while the enzymes were added every sixth day throughout the trial period. The PE dose for all treated tanks was increased by 0.2 ppm after 30 days of culture and another 0.2 ppm after day 60. Meanwhile, fermentation technique, which has become the common method applied in Indonesia in the control treatment, was added on the same day with the PE group with increasing dosage, following the same trend with the 0.6 PE group. Results showed that the group receiving 0.6 PE showed higher final biomass, higher mean weight, and protein retention efficiency as well as a lower feed conversion ratio compared with the control treatment. Abundance of Vibrio spp. remained below 103 cfu mL−1 throughout the trial. Water quality indicators TAN, NO2N and NO3N peaked in weeks 3–5 and then declined after that until the end of the culture period in all tanks. This decline was significantly faster in PE‐treated tanks. Multispecies PEs have potential applications in controlling Vibrio spp., maintaining proper water quality condition, and enhancing the growth of shrimp in intensive culture system.

The effect of dietary carbohydrate to lipid ratios on growth performance in juvenile California yellowtail Seriola dorsalis

Two eight-week feeding trials were conducted to evaluate the effect of dietary carbohydrate to lipid ratios on growth performance on juvenile California yellowtail Seriola dorsalis. In Trial 1, groups of twenty California yellowtail (ca. 6.8 g) were fed five iso‑nitrogenous diets that were formulated to contain decreasing levels of crude lipid from 21% to 6% by replacing menhaden fish oil with corn starch on a weight basis In Trial 2, groups of twenty fish (ca. 5.2 g) were fed five iso‑nitrogenous diets that were formulated using a similar matrix, corn starch 0–24% was used to replace lipids (11.3 to 1.3%) at approximately 2:1 ratio to maintain the diets with similar energy content and the nitrogen free extract (carbohydrates) from 10% to 30% of the diet Fish were fed 5–11% body weight per day over the course of both trials. Growth performance metrics including thermal-unit growth coefficients and protein retention efficiencies were measured and compared using a quadratic regression model. Fish that were fed diets containing high levels of dietary lipids (15% or higher) exhibited decreased growth performance in Trial 1. In Trial 2, fish that received diets containing the highest level of carbohydrates exhibited improved feed efficiency and overall performance. The results from both trials demonstrate that juvenile California yellowtail with a starting size of 5–7 g have an energy fraction preference and display increased growth when fed diets containing a carbohydrate to lipid ratio of up to 5.8.

Dietary tryptophan requirement of fingerling Channa punctatus (Bloch) based on growth, hematological parameters, intestinal enzymes, non-specific immune response, and antioxidant capacity

In this investigation, the tryptophan requirement of C. punctatus fingerling (5.45 ± 0.07 g) was determined by feeding seven isoproteic (450 g kg−1 CP) and isoenergetic (14.7 kJ g−1 DE) diets with graded levels of tryptophan 1, 2, 3, 4, 5, 6, and 10 g kg−1, respectively to randomly stocked groups in triplicate at 8:00, 12:30 and 17:30 h near to satiety for 12 weeks. Tryptophan contributed by casein and gelatin in basal diet was 1 g. To attain the desired tryptophan levels 0, 1, 2, 3, 4, 5 and 9 g kg−1 crystalline tryptophan was added to basal diet. The analyzed value of tryptophan in the experimental diets was found to be 0.9, 1.5, 2.6, 3.3, 4.7, 5.4 and 9.1 g kg−1, and were designated as Tr0.9, Tr1.5, Tr2.6, Tr3.3, Tr4.7, Tr5.4 and Tr9.1. Significant enhancement (P < 0.05) was found in Absolute weight gain (AWG), specific growth rate (SGR), protein retention efficiency (PRE), protein gain (PG), and RNA/DNA ratio with increasing tryptophan content up to 4.7 g kg−1 dry diet. Carcass protein and fat also improved significantly up to 4.7 g kg−1 tryptophan content. Hematological indices such as hematocrit, hemoglobin, red blood cell counts, erythrocyte sedimentation rate were positively affected (P < 0.05) up to 4.7 g kg−1 tryptophan content of the diet. Serum protein, glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and lysozyme were also positively correlated (P < 0.05) up to 4.7 g kg−1 dietary tryptophan content while malondialdehyde (MDA), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) showed the inverse pattern. On subjecting the AWG, FCR, PRE, PG, RNA/DNA ratio, Hb and SOD against dietary tryptophan content to quadratic regression analysis, the tryptophan requirement was found at 5.43, 5.5, 5.21, 4.96, 4.81, 4.85 and 5.39 g kg−1 diet, respectively. Based on the parameters mentioned above, the addition of tryptophan in feed in the range of 4.81–5.5 g kg−1 is recommended for formulating tryptophan balanced, practical feeds for this fish.

Dietary histidine requirement for fingerlings of Channa punctatus (Bloch)

To estimate the requirement of fingerling Channa punctatus (6.34 ± 0.08 g) for dietary histidine, the present study was conducted by feeding six isoproteic (450 g kg−1 CP) and isoenergetic (14.73 kJ g−1 DE) diets with six histidine levels (2.5, 5, 7.5, 10, 12.5 and 15 g kg−1 diet). The trial diets were fed for 12 weeks in a triplicate group of fish at 08:00, 12:30, and 17:30 h to apparent satiation. Absolute weight gain (AWG; 49.1 g fish−1), daily growth index (DGI, 2.34%), feed conversion ratio (FCR, 1.42), protein retention efficiency (PRE; 28.12), and histidine retention efficiency (HRE; 29.69%) improved significantly with increasing histidine from 2.5 to 12.5 g kg−1 diet. Dietary histidine concentrations considerably affected carcass protein, lipid, and moisture contents. Increment in hematocrit (Hct), hemoglobin (Hb), and red blood cell counts (RBCs) were noted with increasing histidine up to 12.5 g kg−1 after that decreased. In contrast, erythrocyte sedimentation rate (ESR) and erythrocyte osmotic fragility (EOF) showed a reverse pattern. Total Serum protein, superoxide dismutase (SOD), and catalase (CAT) activities responded positively up to 12.5 g kg−1 dietary histidine, whereas malondialdehyde (MDA) aspartate aminotransferase (AST) and alanine aminotransferase (ALT) significantly declined up to 12.5 g kg−1 of dietary histidine. Second-order regression of AWG, FCR, PRE, and HRE against different histidine concentrations showed the requirements at 12.2, 11.7, 12.3, and 11.2 g kg−1, respectively. Dietary inclusion of 12.5 g kg−1 histidine is recommended for fingerling C. punctatus for optimum growth, hematological parameters, and antioxidant activities.

Influence of dietary soybean meal replacement with yellow mealworm (Tenebrio molitor) on growth performance, antioxidant capacity, skin color, and flesh quality of mirror carp (Cyprinus carpio var. specularis)

Yellow mealworms (TM) are currently receiving increasing attention as dietary protein source in aquaculture. A 60-day feeding trial was conducted to study the effects of dietary soybean meal (SM) replacement by TM on growth performance, antioxidant capacity, and flesh quality of mirror carp. A total of 630 mirror carp were fed seven diets containing graded concentrations of TM: YM0 (control), YM15, YM30, YM45, YM60, YM75, and YM100, corresponding to 0%, 15%, 30%, 45%, 60%, 75%, and 100% dietary soybean meal replacement. The results indicated dietary TM significantly improved the final body weight (FBW), specific growth rate (SGR), and protein efficiency (PE) (P < 0.05), except for YM100 (P > 0.05). The antioxidant capacity was promoted by increasing muscle total antioxidant capacity (T-AOC) in YM30 and superoxide dismutase (SOD) activity in TM supplemented groups (P < 0.05). The nutritional value was significantly boosted by increasing the muscle protein of YM45 and YM60 groups, the whole-body protein and muscle glycine and proline of YM60 group, and the muscle arginine of YM100 group (P < 0.05). The economic value of mirror carp also increased with the improvement of skin color by increasing yellowness (b*) (P < 0.05). Furthermore, all muscle textural parameters, fiber density, sarcomere length, and the mRNA expression of genes involved in muscle cell growth had similar change trends, increasing initially and then declining with the increase of dietary TM level. The muscle chewiness, cohesiveness, and mfr4 expression in YM15, and the adhesiveness, fiber density, sarcomere length, and mRNA expression of fgf in YM45 were higher than in the control and YM100 (P < 0.05), while no difference was found between control and YM100 (P > 0.05). The mRNA expression levels of myhc and TOR in the muscle of YM60 were significantly higher than those of the control group (P < 0.05), while there was no significant difference in YM100 (P > 0.05). According to the results of principal components analysis (PCA), the muscle textural properties in YM45 were optimal among all groups. As a consequence, TM would be able to completely replace dietary soybean meal without negative influences on growth performance, antioxidant capacity, or flesh quality of mirror carp. Finally, based on FBW, muscle crude protein, muscle fiber diameter, and protein retention efficiency (PRE), the optimal levels of dietary soybean meal replaced by TM were 50.14%, 52.43%, 53.60%, and 55.35%, respectively.