Effect of dietary protein level on growth performance, body composition, and digestive enzyme activities in green mud crab ( Scylla paramamosain ) juveniles

The effects of dietary different protein levels on growth performance, body composition, digestive enzyme activity and fecundity were tested in the oriental river prawn Macrobrachium nipponense. Five iso-energetic and iso-lipidic experimental diets were formulated with graded levels of protein [31.34% (A), 33.87% (B), 36.95% (C), 39.56% (D) and 42.58% (E)]. The results showed that M. nipponense fed diets with 39.56% protein level exhibited the best growth performance, survival, feed conversion rate and protein retention. Following the measurement of digestive enzyme activity in treatment D showed significantly improved (p < 0.05) hepatopancreatic amylase and protease activities compared with treatments A and B. Interestingly, dietary protein levels significantly affected the basal composition of eggs. Furthermore, the dietary protein levels of 36.95% and 39.56% showed significantly higher total protein and lipid content in eggs than the control (31.34%). According to the results of berried females, reduced spawning frequency towards the end of the feeding trial period was observed. Broken-line regression analysis indicated that the optimal dietary protein levels for egg quality are 37% (% dry matter) for juvenile Macrobrachium nipponense.

The present study was conducted to evaluate the individual and combined effects of dietary crude protein levels and magnetic water treatment on the growth performance, water quality, body composition, physiological responses, and immunity of Oreochromis niloticus. Using a 3 × 2 factorial design, three levels of dietary crude protein (25%, 30%, and 35%) and two water types (magnetized and non-magnetized) were tested. A total of 180 juvenile tilapia (average initial weight: 4.13 ± 0.004 g) were randomly assigned to six treatment groups and reared for 10 weeks. Results showed that magnetic water treatment significantly improved dissolved oxygen and pH, while reducing ammonia, nitrite, and nitrate concentrations. Growth performance indicators, including final weight, specific growth rate, feed conversion ratio, and average daily gain, were significantly improved by both magnetic water and increased dietary protein. Carcass crude protein content improved with both the higher dietary protein level and magnetic water, while lipid content decreased. Liver and kidney function indicators (AST, ALT, ALP, and urea) were significantly improved by magnetic treatment and higher protein levels. Blood biochemical markers (TP, ALB, and GLO) were elevated, while glucose, cholesterol, and triglycerides were reduced by magnetic water; significant interactions were observed for globulin, triglycerides, and total protein. Antioxidant enzyme activities (SOD, CAT, and GPx) increased, and MDA decreased in response to magnetic water and high-protein diets. Similarly, digestive enzyme activities (lipase, protease, and amylase) and immune parameters (IgM and lysozyme) were significantly improved, with the best values recorded in the 35% protein + magnetic water group. In conclusion, magnetic water treatment and dietary protein level independently and interactively affect the physiological performance and health of Nile tilapia, with the best outcomes obtained at 35% protein under magnetic water conditions.

A 50-day feeding experiment was conducted to investigate the effects of dietary protein level (26%, 34%, 43% and 52%) on the survival, growth performance, digestive enzyme activities, antioxidant capacity and body composition in the Chinese mitten crab (Eriocheir sinensis) reared at three salinities (0.5‰, 2‰ and 6‰). Survival rate (SR) showed a clearly decreasing tendency as the salinity elevated. The highest weight gain rate (WGR) was achieved in the treatment of 43% protein at the salinity of 0.5‰ and 2‰, and 26% protein at the salinity of 6‰ (p > 0.05). However, there was no significant interactive effect between dietary protein level and salinity on the SR and WGR of E. sinensis (p > 0.05). As salinity increased, the amylase activity and lipid deposition increased but the Na+/K+-ATPase activity decreased. The MDA content of E. sinensis was increased at the salinity of 2‰ than the other two salinities by low or moderate dietary protein (26–43% dry diet), but was significantly decreased by high protein (52% dry diet). Correspondingly, the activities of GSH-Px were increased at the relatively higher protein (43–52% dry diet). The significant interactive effect was only obtained between dietary protein level and salinity on the activities of CAT, GSH-Px and MDA content of E. sinensis. Dietary protein level had a more obvious positive effects on the EAA deposition at the salinity of 2‰ and 6‰, with the highest contents of essential amino acids (EAAs) achieved by 43% dietary protein. In conclusion, the relatively higher protein could benefit the E. sinensis by inhibiting the lipid peroxidation and increasing the deposition of EAAs at the salinity of 2‰. The elevated activities of amylase could account for the low protein (26%) requirement for E. sinensis reared at the salinity of 6‰.

Tributyrin enhances growth and intestinal health in green mud crab (Scylla paramamosain) through butyrate-driven metabolic regulation.

Simple SummaryFive feed protein levels (32%, 36%, 40%, 44%, and 48%) were set up using fishmeal as the sole protein source to study the effects of different feed protein levels on the intestinal microbiota and transcriptome responses of L. vannamei. It was found that the optimal feed protein level for shrimp L. vannamei is between 40% and 44%. Excessively high or low feed protein levels reduce antioxidant levels and digestive enzyme activity and promote pathogen colonization. The transcriptional regulation of inappropriate protein levels responds to the body by reducing factors in various metabolic pathways. The weakened genes impede metabolic processes and compromise immunological function, increasing the organism’s vulnerability to diseases. This can impair the immune systems of shrimp and cause stunted growth.This study explored the effects of dietary protein levels on Litopenaeus vannamei with its intestinal microbiota and transcriptome responses. Previous studies on the effects of dietary protein levels on L. vannamei have focused on growth performance, antioxidant indices, and digestive enzyme activity, but few studies have been conducted at the microbiological and molecular levels. In this study, five isolipid experimental diets with protein levels of 32% (P32), 36% (P36), 40% (P40), 44% (P44), and 48% (P48) were used in an L. vannamei (0.63 ± 0.02 g) feeding trial for 56 days. At the end of the feeding trial, the growth performance, immunity, intestinal health, and transcriptional responses of L. vannamei were determined. This study demonstrated that higher protein levels (P44) led to superior weight gain and growth rates for L. vannamei, with lower feed conversion ratios (FCR) observed in the P48 and P44 groups compared to the P32 and P36 groups (p ≤ 0.05). The P44 and P48 groups also showed a notably higher protein efficiency ratio (PER) compared to others (p ≤ 0.05), and there was no significant difference between them. Upon Vibrio parahaemolyticus infection, the P48 group exhibited a significantly lower survival rate (SR) within 48 h, while during 72 h of white spot syndrome virus (WSSV) infection, the P44 group had a notably higher survival rate than the P32 group (p ≤ 0.05). Digestive enzyme activity and antioxidant levels in L. vannamei initially increased and then decreased as protein levels increased, usually peaking in the P40 or P44 groups. Lower dietary protein levels significantly reduced the relative abundance of beneficial bacteria and increased the relative abundance of pathogenic bacteria in the intestines of L. vannamei. Transcriptome sequencing analysis revealed that most differentially expressed genes (DEGs) were up-regulated and then down-regulated as dietary protein levels increased. Furthermore, KEGG pathway enrichment analysis indicated that several immune and metabolic pathways, including metabolic pathways, glutathione metabolism, cytochrome P450, and lysosome and pancreatic secretion, were significantly enriched. In summary, the optimal feed protein level for L. vannamei shrimp was 40–44%. Inappropriate feed protein levels reduced antioxidant levels and digestive enzyme activity and promoted pathogen settlement, deceasing factors in various metabolic pathways that respond to microorganisms through transcriptional regulation. This could lead to stunted growth in L. vannamei and compromise their immune function.

An 8-week feeding trial was conducted to investigate effects of dietary protein levels (37, 40, and 43%) on the growth performance, feed utilization, digestive enzyme activity, and gene expressions of target of rapamycin (TOR) signaling pathway in fingerling yellow catfish. One hundred and eighty fingerlings (average weight 0.77 ± 0.03g) were equally distributed across four replicate tanks for each of the three treatments, with 15 fish per tank. No difference (P > 0.05) was observed in initial body weight, survival rate (SR), hepatosomatic index (HSI), viscera index (VSI), dressing percentage (DP), and condition factor (CF) among all the treatments. The diet containing 40% protein increased significantly (P < 0.05) final body weight, weight gain rate (WGR), specific growth rate (SGR), protein efficiency ratio (PER), nitrogen retention (NRE), and energy retention (ERE) in fish. The highest protease activity in the stomach and intestine was observed in the P40 group (P < 0.05), while amylase and lipase were not significantly different (P > 0.05). The transcriptional levels of IGF-1, IGF-1R, and Akt were significantly (P < 0.05) higher in fish fed P40 or P43 than those of fish fed P37. TOR and S6K1 mRNA expressions were significantly (P < 0.05) increased in the P40 groups. Hence, the diet containing 40% protein would be suitable for the optimum growth and effective protein utilization of fingerling Pelteobagrus fulvidraco. In vitro, the transcriptional levels of IGF-1, IGF-1R, Akt, TOR, and S6K1 in hepatocyte supplemented with a 40-μM mixed amino acids were significantly (P < 0.05) higher compared to other treatments. No difference (P > 0.05) was observed in eukaryotic translation initiation factor 4E-binding protein 1 in vivo and in vitro among all the treatments. Effects of dietary protein level on growth performance likely are involved in the activation of TOR signaling pathway in fingerling Pelteobagrus fulvidraco.

Simple SummaryThe shortage of fishmeal is currently a pressing issue for the aquaculture industry, as it increases the cost of aquatic product production and contributes to overfishing in the oceans. To solve this problem, Chlorella sorokiniana has started to be used in recent years as a major protein source in aquatic animal diets. However, differences in dietary protein sources will result in different optimal protein requirements. Accordingly, this study determined the growth performance, body composition, intestinal digestion and microbiota of Litopenaeus vannamei fed with five isolipid diets using C. sorokiniana as the main protein source but in different protein levels. The results showed that a dietary protein level of 40.81% resulted in the best weight gain rate when C. sorokiniana was used as the main protein source. Additionally, the optimal nutritional composition, digestibility and intestinal microbiota stability of L. vannamei occurred at a 40% dietary protein level. Higher dietary protein levels increased the colonisation of beneficial bacteria and inhibited the colonisation of pathogenic bacteria. These data inform the scientific application of C. sorokiniana in L. vannamei diets and promote the sustainable development of L. vannamei farming.This study investigated the effect of dietary protein levels on Litopenaeus vannamei. Five isolipid diets with protein levels of 32%, 36%, 40%, 44% and 48% were prepared using C. sorokiniana as the main protein source. L. vannamei (initial body weight 0.83 ± 0.02 g) were fed these five diets for 8 weeks and referred to as the CHL32, CHL36, CHL40, CHL44 and CHL48 groups, respectively. When the feeding trial was finished, the growth performance, body composition, intestinal digestion and microbiota of L. vannamei were studied. The results showed that the maximum weight gain rate (WGR) of L. vannamei was in the CHL40 group while the lowest feed conversion ratio (FCR) was in the CHL48 group. According to the regression analysis using WGR as the evaluation index, the best growth performance of L. vannamei was obtained when the dietary protein level was 40.81%. The crude protein content of whole shrimp showed an increasing and then decreasing trend with increasing dietary protein levels. Furthermore, the L. vannamei muscle amino acid composition was relatively stable and, to some extent, independent of dietary protein levels. Trypsin, lipase and amylase (AMS) activity increased and then decreased with increasing dietary protein levels and, significantly, peaked in the CHL44 group. Analysis of the alpha diversity of the intestinal microbiota showed that the Chao1 index peaked in the CHL40 group and was significantly lower in the CHL48 group. Additionally, the relative abundance of pathogenic bacteria decreased significantly while the relative abundance of beneficial bacteria increased significantly in the intestine of L. vannamei as the dietary protein levels increased. The functional prediction of the intestinal microbiota revealed that dietary protein levels may influence the growth of L. vannamei by regulating various metabolic activities, and the highest WGR in the CHL40 group may have been related to the significant enrichment of nicotinate and nicotinamide metabolism and biotin metabolism functions. In summary, the optimal protein requirement for L. vannamei was around 40% when C. sorokiniana was used as the primary protein source. Too high or too low dietary protein levels could adversely affect shrimp body composition, intestinal digestion and microbiota.

We studied the effects of dietary protein levels and water temperatures on growth performance, body composition, serum biochemistry, and digestive gland antioxidant enzyme activities of juvenile hybrid abalones Haliotis discus hannai♀ × H. fulgens♂ ( 1.47 ± 0.03 g ; 20.73 ± 0.16 mm ). A 3 × 6 factorial design feeding trial was conducted with three water temperatures (19°C, 23°C, and 27°C) and six protein levels (152.5, 202.5, 252.6, 302.6, 352.7, and 402.7 g/kg) for 90 days. Dietary protein levels and temperature significantly affected the growth performance of the hybrid abalones, but there was no interaction effect except for daily increment in shell length. Body moisture decreased with increasing water temperature, and crude protein showed a contrary tendency. Crude lipid and ash were not affected by dietary protein level or water temperature. The alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities and the triglyceride content in serum increased with increasing water temperature, whereas the opposite was true for albumin activity and total protein and glucose contents. Total cholesterol contents decreased with increasing dietary protein levels. Dietary protein levels and water temperature did not affect contents of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol ( P &gt; 0.05 ). A significant interaction was observed between dietary protein levels and water temperature in all antioxidation parameters (reactive oxygen species, total antioxidant capacity, protein carbonyl, superoxide dismutase, catalase, glutathione s-transferase, and glutathione peroxidase except for malondialdehyde content). Based on specific growth rate, the optimal dietary protein levels for juvenile hybrid abalones were 333.1, 318.6, and 306.3 g protein/kg diet at 19°C, 23°C, and 27°C, respectively. These findings will help to develop multidiet feeding strategies at different water temperatures throughout the culture period of juvenile hybrid abalones.

Effects of dietary protein levels on growth, muscle composition, digestive enzymes activities, hemolymph biochemical indices and ovary development of pre-adult red swamp crayfish (Procambarus clarkii)

Pasinato, A., Elizalde, J., Tisocco, O., Teira, G., Perlo, F. and Bonato, P. 2008. Effect of dietary crude protein level on quality and production of meat in Holstein steers. J. Appl. Anim. Res., 33: 169–173. To characterize the effect of dietary crude protein level on quality and production of meat in Holstein steers, they received complete diets with the same metabolizable energy concentration but different protein content: 12, 14 and 17%, respectively. The average daily live weight gain was 1.32±0.17 kg/head.day−1 without differences among treatments (P>0.05). The group that received the highest level of protein consumed more dry matter (P<0.05) and had lower feed conversion than the group of animals with the diet with 12% crude protein. There were no differences (P>0.05) in the chemical composition of meat among the three treatments. The pH values of all the animals were in the range of an optimum value (5.54 to 5.70). There were no marked effects of the dietary protein level on meat production and quality.

A 12-week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole-body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%.

A feeding trial was conducted using isoenergetic practical diets to evaluate the effects of the dietary protein level on growth performance, feed utilization and digestive enzyme activity of the Chinese mitten crab, Eriocheir sinensis. Four experimental diets were formulated containing 250, 300, 350 and 400 g kg−1 protein and 16 kJ g−1 gross energy. Each diet was randomly assigned to triplicate groups of juvenile crab with mean initial body weight 3.56 ± 0.16 g and mean shell width 15.31 ± 0.06 mm. Juvenile crab were reared in indoor flow-through system consisting of 12 plastic tanks (1.0 m × 0.6 m × 0.5 m) and fed diets twice daily at 6–8% of body weight for 12 weeks. Performance was judged on the basis of growth (specific growth rate of weight, SGRG; specific growth rate of shell width, SGRSW), feed conversion ratio (FCR) and protein efficiency ratio (PER). A decreased FCR was observed with increasing dietary protein levels. Both SGRG and SGRSW significantly increased with increasing dietary protein levels up to 350 g kg−1, whereas there were no significant differences for protein levels from 350–400 g kg−1. Application of broken line regression analysis to SGRG provided an estimate of 347.8 g kg−1 dietary protein for maximal growth. The highest PER was observed in crab fed the diet containing 350 g kg−1 protein (P 0.05) by the different dietary treatments. No significant differences were observed in the apparent digestibility coefficients of crude lipid and dry matter among dietary treatments (P > 0.05). However, the apparent digestibility coefficients of crude protein and energy in crab fed different protein levels significantly increased with increasing dietary protein level (P 0.05) were founded with protein levels higher than 350 g kg−1.

A 52-day experiment was conducted to determine the effect of varying dietary protein levels on juvenile matrinxã Brycon amazonicus, and to evaluate their resulting growth performance, hematological parameters and enzymatic activities. Sixty fish (29.03 ± 1.16g) were distributed in 12 tanks (310 L) with a completely randomized design, and maintained at four dietary crude protein levels (270, 320, 350, 390 g.kg-1 ). The results revealed that the fish fed diet 390 g.kg-1 CP had the best final weight, weight gain, feed conversion ratio, specific growth rate, protein efficiency ratio and lipid retention rate. The same could be stated for hematocrit, number of circulating erythrocytes, triglycerides and total proteins of the hematological profile (p&lt;0.05). For whole body composition, dry matter content was lower in the fish fed 390 g.kg-1 CP, while lipid content was higher in the fish fed 350-390 g.kg-1 CP (p&lt;0.05). No differences were observed in CP and ash (p&gt;0.05), or in the activities of digestive enzymes (p&gt;0.05). In short, our findings suggest that 390 g/kg-1 CP in diet increases zootechnical performance indices in juvenile matrinxã.

An 8-week rearing trial was designed to estimate the dietary protein requirement and evaluate the effects of dietary protein on growth performance, plasma parameters, and digestive enzyme activities of blunt snout bream at two growth stages. Six practical diets were prepared to feed two sizes of fish (larger fish: initial weight of 153.69 ± 0.85 g; smaller fish: initial weight of 40.89 ± 0.28 g) with graded protein levels (26%, 28%, 30%, 32%, 34%, and 36%). Our results show that the final weight, weight gain (WG), and specific growth rate (SGR) of the fish initially rose to peak values and then declined as the dietary protein levels increased. The higher WG and SGR were recorded in the larger fish fed diets containing 30%, 32%, and 34% protein, and in the smaller fish fed a 30% protein diet, all significantly higher than those in the control group (p &lt; 0.05). No significant differences were observed in the feed conversion ratio (FCR), viscerosomatic ratio (VR), hepatosomatic index (HSI), condition factor (CF), or survival rate among the treatments at both growth stages (p &gt; 0.05). The plasma total protein (TP) content was highest at both growth stages in fish fed a 30% protein diet (p &lt; 0.05). As the dietary protein level increased, the plasma urea content of the larger fish increased, peaked in the 34% protein group (p &lt; 0.05), and then remained stable. In contrast, no significant difference in the plasma urea content was seen among the treatment groups of the smaller fish (p &gt; 0.05). Protease activity in the fish foregut at both growth stages peaked in the 32% protein group (p &lt; 0.05). In the midgut of the larger fish, protease activity was higher in the control group, while in the smaller fish, it was higher in the 36% protein group (p &lt; 0.05). In the larger fish, hindgut protease activity was higher in the 34% protein group (p &lt; 0.05), while in the smaller fish, there was no significant difference in the hindgut protease activity among all groups (p &gt; 0.05). The dietary protein levels had no significant effect on lipase activity in the foregut, midgut, or hindgut, or on amylase activity in the foregut or midgut of the fish at the two growth stages (p &gt; 0.05). However, hindgut amylase activity was highest in the control group of the smaller fish (p &lt; 0.05). Based on regression analysis, the optimal dietary protein levels for the larger and smaller fish were 30.45% and 29.95%, respectively. Overall, appropriate dietary protein levels (30%) could improve the growth performance, immune function, and health status of fish at two growth stages and promote the adaptive response of their digestive system, especially the spatial regulation of protease activity in different gastrointestinal regions.

Effects of dietary protein levels with various stocking density on growth performance, whole body composition, plasma parameters, nitrogen emission and gene expression related to TOR signaling of juvenile blunt snout bream (Megalobrama ambylcephala)