Effects of Dietary Protein Levels on Macrobrachium rosenbergii Reared Under a High-Density Culture Model: Growth, Immune Response, Hepatopancreatic Health, and Antistress Capacity

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.

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.

A feeding trial was conducted to investigate the effects of dietary graded protein levels on the growth, survival, amylase and trypsin activities of large yellow croaker (Pseudosciaena crocea R.) larvae from 12 to 42 days after hatching (DAH). Five approximately isoenergetic microbound diets (16.65 MJ/kg diet) were formulated to contain different protein (47.1%, 52.0%, 57.1%, 62.2% and 67.5%) levels. Frozen copepods, containing 54.5% crude protein (CP), 6.0% crude lipid, 27.2% ash and 6.7% glycogen, were used as a control. Each diet was randomly fed to triplicate groups of larvae with an initial mean body weight of 1.76 ± 0.09 mg (mean ± SD) in 180 L white plastic tanks, and each tank was stocked initially with 3500 larvae. Both the survival and the specific growth rate (SGR) of large yellow croaker larvae significantly increased with increasing dietary protein level up to 57.1%, and decreased thereafter. Frozen copepods resulted in intermediate survival and low SGR compared with the other diets. Whole-body moisture and protein of larvae were not significantly affected by the dietary protein level. In contrast, whole-body lipid of larvae fed diet with 47.1% CP was significantly higher (P<0.05) than those from fish fed the diets containing more than 57.1% CP. Additionally, fish fed the frozen copepods had the lowest whole-body protein and lipid. The amylase-specific activity increased with increasing dietary carbohydrate level during the period of this experiment. However, trypsin activity was not significantly affected by the dietary protein content before 42 DAH, indicating a later onset of trypsin than amylase in the regulation of enzymatic synthesis induced by a dietary substrate.

The aim of this study is to investigate the effect of dietary protein levels on flesh quality, oxidative stress, and autophagy status in the muscles of triploid crucian carp (Carassius carassius triploid), and the related molecular mechanisms. Six experimental diets with different protein levels (26%, 29%, 32%, 35%, 38%, 41%) were formulated. A total of 540 fish with an initial weight of 11.79 ± 0.09 g were randomly assigned to 18 cages and six treatments with three replicates of 30 fish each for 8 weeks feeding. It could be found that the whole-body ash content significantly increased in high protein level groups (p < 0.05). The 29% dietary protein level group exhibited the highest muscle moisture, although there was an inconspicuous decrease in the chewiness of the muscles when compared with the other groups. The dietary protein level influenced the content of free amino acids and nucleotides, especially the content of flavor amino acids, which exhibited an increasing tendency along with the increasing protein level, such as alanine and glutamic acid, while the flavor nucleotides showed different fluctuation trends. Moreover, the genes related to muscle development were shown to be influenced by the dietary protein level, especially the expression of MRF4, which was up-regulated with the increasing dietary protein levels. The 29% dietary protein level promoted the majority of analyzed muscle genes expression to the highest level when compared to other dietary levels, except the Myostain, whose expression reached its highest at 38% dietary protein levels. Furthermore, the effect of dietary protein levels on antioxidant signaling pathway genes were also examined. High protein levels would boost the expression of GSTα; GPX1 and GPX4α mRNA expression showed the highest level at the 32% dietary protein group. The increasing dietary protein level decreased both mRNA and protein expressions of Nrf2 by up-regulating Keap1. Autophagy-related gene expression levels reached the peak at 32% dietary protein level, as evidenced by a similar change in protein expression of FoxO1. In summary, muscle nutritional composition, antioxidative pathways, and autophagy levels were affected by the dietary protein levels. A total of 29-32% dietary protein level would be the appropriate level range to improve muscle quality and promote the antioxidant and autophagy capacity of triploid crucian carp muscles.

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.

This study examined the effect of dietary protein and lipid levels on growth, feed utilization and body composition of Asian catfish Pangasius hypophthalmus reared in cages. Eight test diets were formulated at four protein (340, 380, 420 and 460 g kg−1 crude protein) and two lipid (50 and 90 g kg−1 crude lipid) levels. Fish (initial weight 4.7 g fish−1) were fed the test diets for 8 weeks. Final body weight, weight gain (WG), feed intake (FI), feed conversion ratio (FCR), contents of crude protein, lipid and energy in whole body were dependent on both dietary protein and lipid levels, while specific growth rate (SGR), hepatosomatic index and body moisture content were dependent on dietary lipid level. The WG and SGR increased with the increase in either dietary protein level (at the same lipid level) or lipid level (at the same protein level). The FI and FCR decreased with the increase in dietary protein level (at the same lipid level) or lipid level (at the same protein level). Protein sparing action occurred in case dietary lipid level increased. Fish fed the diet containing 453 g kg−1 crude protein and 86 g kg−1 lipid had the highest WG and SGR, but the lowest FI and FCR, among the diet treatments. There were no significant differences in the protein retention efficiency (PRE) and energy retention efficiency (ERE) among the diet treatments, although PRE and ERE were relatively high in fish fed the diet containing 453 g kg−1 crude protein and 86 g kg−1 lipid. At the end of the feeding trial, body protein content increased, while body lipid content decreased, with the increase in dietary protein content at the same lipid level. Our results suggest that dietary levels of 450 g kg−1 crude protein and 90 g kg−1 lipid are adequate to support fast growth of P. hypophthalmus reared in cages.

An 8-week feeding trial was conducted to assess the effects on growth, antioxidant capacity, digestive enzyme activity, and gene expression related to muscle growth and protein synthesis of juvenile greasyback shrimp (Metapenaeus ensis) using five experimental diets containing 29.37%, 34.30%, 39.11%, 44.05%, and 49.32% of protein. The results demonstrated that juvenile greasyback shrimp consuming 39.11%, 44.05%, and 49.32% dietary protein had a significantly higher final body weight (FBW), weight gain (WG), feed conversion ratio (FCR), and specific growth rate (SGR) than other groups (p < 0.05). The protein efficiency ratio (PER) showed a significantly quadratic pattern with increasing dietary protein levels (p < 0.05). The highest trypsin and pepsin activities were observed in the group with a protein level of 44.05% (p < 0.05). Relatively higher superoxide dismutase (SOD) activity was found in groups with protein levels of 39.11% (p < 0.05). Alkaline phosphatase (AKP) and catalase (CAT) activity showed a significantly linear increasing pattern with increasing protein intake up to 44.05%, and then decreased gradually (p < 0.05). Compared to the dietary 29.37% protein level, the expression levels of myogenic regulatory factors (mef2α, mlc, and myf5) and mTOR pathway (mtor, s6k, akt, and pi3k)-related genes were significantly up-regulated in muscle with 39.11%, 44.05%, and 49.32% dietary protein levels (p < 0.05). The AAR pathway (gcn2, eif2α, and atf4)-related gene expression levels were significantly lower in muscles with 39.11%, 44.05%, and 49.32% protein levels than in other groups (p < 0.05). Based on the broken-line regression analysis of SGR, the estimated appropriate dietary protein requirement for juvenile greasyback shrimp is 38.59%.

Growth and feed utilisation of juvenile greenlip abalone (Haliotis laevigata) in response to water temperatures and increasing dietary protein levels

Effects of dietary protein level on growth performance, nitrogen and energy budget of juvenile hybrid sturgeon, Acipenser baerii ♀ × A. gueldenstaedtii ♂

A 3 × 2 factorial experiment (protein levels, 42%, 46%, 50%; lipid levels, 9%, 12%) with three replicates was conducted in a circulating water system to investigate the effects of dietary protein and lipid levels on growth, feed utilization, body composition, and serum biochemical parameters of growing rockfish Sebastes schlegeli (initial weight, 29.98 ± 0.10 g). After an 8 weeks feeding trial, growth performance in terms of final body weight, percent weight gain, and specific growth rate increased with the increase of dietary protein level when fish fed diets containing a consistent level of dietary lipid. The feed conversion rate and daily feed intake were significantly affected by dietary protein and lipid levels, and decreased as dietary protein level increased from 42% to 46% or dietary lipid level increased from 9% to 12% (P < 0.05). Survival rate, viscerosomatic index, and hepatosomatic index were unaffected by dietary protein level (P > 0.05), but significantly increased with the increase of dietary lipid level (P < 0.05). On the contrary, condition factor was unaffected by dietary lipid level (P > 0.05), but significantly increased with dietary protein level increasing up to 46% (P < 0.05). The moisture contents of muscle and liver significantly decreased, but the whole-body crude lipid content, the crude protein and lipid contents of muscle increased as dietary protein or lipid level increased (P < 0.05). The contents of isoleucine, leucine, histidine, glycine, alanine of muscle, as well as the proportions of C14 : 0, C20 : 1, and C22 : 1n-9 in total fatty acids were higher in fish fed diets containing 12% lipid than those fed 9% lipid (P < 0.05), while C18 : 1n-9 and C18 : 2n-6 followed an opposite trend. The contents of phenylalanine, lysine, and tyrosine as well as the proportions of C18 : 0, C18 : 2n-6, C22 : 1n-9, and C22 : 6n-3 in total fatty acids decreased with the increase of dietary protein level (P < 0.05). Serum cholesterol and low-density lipoproteins increased significantly with dietary protein or lipid levels increasing, but TG concentration was elevated significantly in fish fed diets containing 12% lipid. Considering the present results in terms of growth and feed utilization, the suitable protein and lipid levels in diet for growing rockfish were 46% and 12%, respectively.

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.

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.

Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot was determined at optimum salinity and temperature conditions of 17 g L−1 and 19.2 °C, respectively, by using 3 × 2 (protein levels: 550, 600 and 650 g kg−1; lipid levels: 69 and 168 g kg−1) factorial design with three replications of each. Fish were hand-fed to satiety twice daily throughout the feeding trial. Weight gain and specific growth rate of fish were significantly (P < 0.05) increased with increased dietary lipid level, but not by dietary protein level. Daily feed intake was significantly (P < 0.05) affected by both dietary protein and lipid levels. Feed efficiency ratio and protein efficiency ratio were significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Moisture content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Crude lipid content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Significantly higher 20:5n−3, 22:6n−3 and n−3 highly unsaturated fatty acids were observed in turbot fed the low lipid diet than fish fed the high lipid diet in all protein levels, but significantly lower 18:2n−6 was observed in fish fed the former compared with the latter. In considering results of growth, specific growth rate and efficiency of feed, optimum dietary protein and lipid levels for juvenile turbot seemed to be 550 and 168 g kg−1 of the diet, respectively, under optimum salinity and temperature conditions.

Juvenile Nibea diacanthus were fed various dietary protein levels, and their growth performance, feed utilization, carcass proximate composition and 24-h postprandial ammonia–nitrogen excretion were investigated. Five isoenergetic and isolipidic experimental diets, containing various protein levels ranging from 36 to 52 % by a 4 % increment, were formulated. Each diet was randomly fed to triplicate groups of 25 juvenile N. diacanthus (initial weight 62.85 ± 0.32 g) for 8 weeks. Highest weight gain, specific growth rate, feed efficiency, protein efficiency ratio and protein retention were obtained at 48 % dietary protein levels (P < 0.05). As dietary protein levels increased, feed intake, hepatosomatic index and viscerosomatic index declined significantly. Similarly, the ammonia–nitrogen excretion rate was largely inversely correlated with dietary protein levels, with the lowest value appearing in the 48 % group (P < 0.05). High-protein diets resulted in higher whole-body and muscle protein contents and produced a significant effect on muscle amino acid profile. Also, total essential amino acid pattern of the muscle was significantly correlated to those of dietary proteins. Analysis of specific growth rate and weight gain by broken-line regression indicated that the estimated optimal dietary levels of protein for juvenile N. diacanthus were 48.66–48.94 %.

Seven isoenergetic semi-purified test diets containing graded levels of protein ranging from 20 to 50% were formulated using fish meal and casein as the protein sources. Test diets were fed to triplicate groups ofBarbodes caldwellijuveniles with initial body weights of 1.26±0.02 g for eight weeks. The results indicated no significant effect of dietary protein levels on survival rate, relative weight of the viscera and relative weight of the liver in the juvenile fish. The weight gain and specific growth rate of the fish were found to be greater as dietary protein levels increased from 20 to 35%, but were not affected significantly as dietary protein level increased from 35 to 50%. Feed efficiencies did not differ significantly when fish were fed diets with protein levels from 30 to 50%, but were significantly higher than those of fish fed diets with protein levels of 20 and 25%. The protein efficiency ratio (PER) was negatively correlated with diet protein level (x) (PER=3.006−0.03251x,R=0.9366). There was no significant effect of dietary protein levels on carcass moisture, crude protein and ash. However, carcass lipid levels (L) decreased with an increase in dietary protein level (x) (L=8.2169−0.0458x,R=0.8551). There was no significant variation in hepatopancreas protease activity among the tests. Intestine protease activity and hepatopancreas amylase activity were increased to some extent, and then decreased as dietary protein levels continued to rise. The intestine amylase activity (IAA) of the juveniles was negatively correlated with dietary protein level (x) (IAA=84.625−0.9147x,R=0.8463). It was estimated that the suitable protein level for theB. caldwellijuvenile is 34% (the broken-line model was used to regress the relationship of the weight gain of the juvenile and dietary protein level).