Optimum Dietary Protein Research Articles

Protective effects of dietary protein against nitrite stress in grass carp (Ctenopharyngodon idella): A new perspective

Protein constitutes the predominant essential nutrient in fish feed. Despite extensive research efforts on the dietary protein of fish, limited attention has focused on its potential antistress properties. Therefore, this study sought to examine the impact of dietary protein on the liver structure of grass carp (Ctenopharyngodon idella) and its underlying molecular mechanism after nitrite stress, with the objective of elucidating the role of dietary protein in the stress response of fish. Specifically, various levels of dietary protein (16 %, 19 %, 22 %, 25 %, 28 % and 31 %) were investigated for their effects on liver tissue damage, oxidative stress, endoplasmic reticulum (ER) stress, autophagy and apoptosis in grass carp after exposure to a nitrite solution at a concentration of 10 mg/L for a duration of 96 h.Our study revealed that exposure to nitrite solution resulted in liver structural damage in grass carp. However, 22–25 % dietary protein levels might attenuate the impact of nitrite stress by decreasing liver contents of nitric oxide (NO), peroxynitrite anion (ONOO-), reactive oxygen species (ROS), protein carbonyl (PC), and malondialdehyde (MDA), which is reflected in serum activities of glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT). Histological analysis further supported the protective role of appropriate protein levels (22–28 %) in alleviating nitrite-induced liver tissue damage. Subsequent investigations demonstrated that optimal dietary protein levels decreased ER stress and autophagy in fish by modulating the expression of gene and protein involved in 78 kDa glucose regulated protein (GRP78) pathway and autophagosome formation process, respectively. Meanwhile, appropriate dietary protein levels decreased the activities of caspase-3, caspase-8 and caspase-9 by inhibiting both death receptor pathway and mitochondrial pathway associated with apoptosis. Finally, based on regression analysis of liver ONOO− content, the dietary protein requirement for grass carp (721–1381 g) under nitrite stress was determined to be 25.07 %. Overall, this study provides novel evidence that optimal protein levels can enhance the resistance of grass carp to nitrite stress and mitigate liver tissue damage by reducing oxidative stress cascade damage.

The Effect of the Species Source of Muscle and/or Digestive Enzymes on the Utilization of Fish Protein Hydrolysates as a Dietary Protein Source in First Feed for Larval Walleye (Sander vitreus).

Fish protein hydrolysates used in larval diets have been prepared from a variety of fish species, with different enzymes used to hydrolyze the protein. This study's objectives were to determine the effect of the dietary inclusion of fish muscle hydrolysates obtained from species-specific muscle/enzymes-versus hydrolysates produced from muscle/enzymes of a different species-on the growth performance, survival, skeletal development, intestinal peptide uptake, and muscle-free amino acid (FAA) composition of larval Walleye (Sander vitreus). Eight protein products were obtained for this study, comprising an unhydrolyzed and hydrolyzed product from each combination of muscle/enzymes from Walleye and Nile tilapia (Oreochromis niloticus). Four diets were produced, and the dietary protein was provided in a 50/50 ratio of unhydrolyzed and hydrolyzed protein from the respective muscle/enzyme combination. Four groups were fed one of the corresponding formulated diets, and two groups of larvae, fed a commercial starter diet and Artemia, respectively, served as reference groups. Larval Walleye fed the diet containing protein produced with the species-specific muscle and enzymes had a significantly higher weight after the study-30% higher than any other group. A significant interaction effect between muscle and enzyme sources on the growth of Walleye larvae was observed. The species-specific combination also led to a significant increase in postprandial FAA and indispensable amino acid concentrations in muscle. No significant differences were observed between the hydrolysate-fed groups in survival, deformity occurrence, or peptide uptake. Each hydrolysate-based diet significantly reduced skeletal deformities and survival compared to the commercial diet. The results of this study suggest that species-specific muscles and enzymes produce a more optimal dietary protein source for larval fish than non-species-specific products. Further research should focus on improving the physical properties of the formulated diets to reduce possible leaching of hydrolyzed protein and improve the survival of fish larvae.

Effects of dietary protein levels on growth performance, hemato–biochemical, and immune parameters in ship sturgeon (Acipenser nudiventris) juveniles

A feeding trial was conducted to detect the optimal dietary protein requirement for ship sturgeon (Acipenser nudiventris) juveniles. Four isoenergetic diets were formulated to contain different protein levels i.e. 40 % (P40), 45 % (P45), 50 % (P50), and 55 % (P55). A total of 180 ship sturgeon juveniles, with an average weight of 63.5 ± 1.3 g, were randomly distributed into triplicated groups (15 fish per tank) and fed on the experimental diets for 10 weeks. Significant (P < 0.05) increases in growth indices and feed intake were noted with increasing dietary protein levels up to 50 % after which (P55) fish growth was declined. The highest values of protein and lowest value of lipids and ash contents were noted in the whole-body of fish fed on the P50 diet. The levels of red blood cells, hemoglobin, and hematocrit were markedly influenced (P < 0.05) by varying dietary protein concentrations, and the most elevated values were identified in the P50 treatment. Linear increases were observed in alanine aminotransferase and alkaline phosphate levels; while quadratic increases were observed in aspartate aminotransferase activities due to the increase in dietary protein levels. Quadratic increases in total protein (TP), total immunoglobulin (total Ig), and lysozyme (LYZ) were observed due to feeding the fish on higher protein levels. The highest level of TP was significantly (P < 0.05) found in P50 and P55 with no significant (P > 0.05) difference between them. Levels of total Ig and LYZ were significantly (P > 0.05) highest in the P50 treatment. Based on the regression fitting curves of growth indices, the optimum dietary protein level for ship sturgeon (A. nutiventis) juveniles is found to be 46.5 % – 50 %. Data AvailabilityAll data of this study are included in this article.

Dried porcine soluble augments dietary fishmeal replacement by poultry by-product meal for large yellow croaker Larimichthys crocea

Two concurrent feeding trials was conducted to assess the effects of replacing fishmeal with poultry by-product meal (PBM) and supplementing dried porcine soluble (DPS) in large yellow croaker Larimichthys crocea diets at the optimal dietary protein level. In trial I, the reference diet (F40) contained fishmeal at 400 g/kg, and 40%, 60% and 80% of the fishmeal was substituted with PBM (the diets were termed as F24, F16 and F8). In trial II, the control diet (F16D0) contained fishmeal at 160 g/kg, and DPS was added at 4, 8, 12 and 16 g/kg in F16D0 (the diets were termed as F16D4, F16D8, F16D12 and F16D16). Fish initially weighing 20.0 ± 0.2 g were fed the test diets for 10 weeks. Fishmeal replacement level significantly influenced final body weight (FBW), weight gain, feed conversion ratio, nitrogen and energy retention efficiencies, ratio of fish-in to fish-out (FIFO), feed cost, activity of superoxide dismutase and catalase in plasma and liver, activity of glutathione peroxidase in plasma, and malondialdehyde content in liver. However, neither fishmeal replacement level nor DPS supplementation level resulted in significant change in condition factor, hepatosomatic index and body composition. There were no significant differences in weight gain and FBW either between F40, F24 and F16 or between F40 and F16D0, F16D4, F16D8, F16D12 and F16D16. The FBW of F16 declined by 3.2% relative to F40, while the FBW of F16D12 increased by 10.1% relative to F16D0. This study reveals that dietary fishmeal level for large yellow croaker could be reduced to 160 g/kg by using PBM as a sole substitute, and DPS supplementation could augment dietary fishmeal replacement by PBM.

High protein requirements of juvenile Atlantic wolffish, Anarhichas lupus: Effects of dietary protein levels on growth, health, and welfare.

The objective of the present study was to investigate the optimal dietary protein requirement and the effect of varying protein levels on the growth and health of juvenile, wild-caught Atlantic wolffish, Anarhichas lupus, a promising candidate for cold-water aquaculture diversification. Six iso-energetic (ca. 18.3 MJ kg-1), fish meal-based experimental diets were formulated with crude protein levels ranging from 35% to 60%, with graded increments of 5% in a 12-week feeding trial in a recirculating aquaculture system (RAS). Weight gain, specific growth rate (SGR), and condition factor (K) were evaluated in response to dietary protein levels. Liver, muscle, and blood parameters were assessed for possible changes in protein and lipid metabolism and welfare. Overall growth was highly variable throughout the experiment on all diets, as expected for a wild population. The feed with highest in protein (60%) inclusion resulted in the highest growth rates, with an average weight gain of 37.4% ± 33.8% and an SGR of 0.31% ± 0.2% day-1. This was closely followed by feeds with 55% and 50% protein inclusion with an average weight gain of 22.9% ± 34.8% and 28.5% ± 38.3%, respectively, and an SGR of 0.18% ± 0.3% day-1 and 0.22% ± 0.3% day-1, respectively. Fish fed the high protein diets generally had increased hepatic lipid deposition (17%-18%) and reduced free fatty acid levels (3.1-6.8 μmol L-1) in the plasma relative to fish that were fed the lower protein diets (35%-45%). No effects of diet were found on plasma protein levels or muscle protein content. Furthermore, stress parameters such as plasma cortisol and glucose levels were unaffected by diet, as were plasma ghrelin levels. Overall, these results suggest that a high protein inclusion in the diet for Atlantic wolffish is required to sustain growth with a minimum protein level of 50%.

#655 Warm meal after a haemodialysis session saves the day (and lives?)

Abstract Background and Aims The haemodialysis (HD) process leads to chronic nutrient deficiency, particularly of proteins and amino acids. About 6-12 grams of amino acids loss and 7-8 grams of protein loss occurring during each dialysis session may contribute to hypoalbuminemia, a strong predictor of malnutrition and mortality [1]. Optimal dietary protein intake (DPI) may replenish low plasma amino acids, but DPI inadequacy is a common issue in HD patients, as well as malnutrition due to comorbidities. COVID-19 has made dramatic changes in dialysis centers’ procedures, including the transition from warm meals to cold sandwiches for patients to eat after the session. After the end of COVID-19 pandemic warm meals (meat dish included) were reintroduced. Our aim was to quantify the effect of one to three warm meals per week after the HD session (depending on the regime) on the patients’ protein status. Method Data of 68 patients (24 females and 44 males) on chronic HD were collected after signing the ICF consisting of total protein and albumin values measured two months apart. The first measurement was done while patients were on the long-term sandwich diet after every HD session. The second measurement was done 45 days after the warm meal diet was initiated after every session. Serum total protein and serum albumin were measured, with normal intervals for total serum protein and albumin being 66–81 g/L and 45–51 g/L respectively. The values were compared using Wilcoxon signed-rank test. Results The average albumin value with dry food was 35.9 g/L and for total protein 63.6 g/L, with just 6 patients having normal albumin levels (8.8%) and 21 patients having normal total protein levels (30.9%). The average albumin value after 45 days of HD with warm meals was 39.8 g/L and 66.6 g/L for total protein, with 28 patients having normal albumin levels (41.2%) and 36 patients having normal total protein levels (52.9%). This marks an increase of 4.7% in average value of total protein (3 g/L) and statistically significant increase in albumin value of 10.8% (3.9 g/L, p &amp;lt; 0.001). Greater number of patients had normal total protein and albumin values (4.7 times more patients had a normal albumin level after the initiation of warm meals, and 1.7 times more patients had normal total protein levels). There is a difference regarding male and female patients with a greater impact on males. Male patients had an average total proteins value increase of 5.3% (3.37 g/L) while female patients had 3.5% (2.29 g/L). There was a statistically significant increase in albumin value both for male (p &amp;lt; 0.001) and female patients (p = 0.002). In male patients the average increase was 12% (4.33 g/L), while in female patients it was 8.5% (3.04 g/L). After the introduction of warm meals, 50% of male patients had normal albumin values (vs. 9% before), while 25% of female patients reached normal albumin values (vs. 8.3% before). Conclusion Patients on chronic HD suffer from malnutrition which could lead to significantly higher mortality. Adequate nutrition is crucial for their wellbeing. This study has shown that having a warm meal (protein based) can lead to an increase of total plasma protein and albumin with a higher impact on male patients. In this way we could increase DPI of HD patients, reduce the chance of malnutrition and reduce the cardiovascular risk and mortality.

An approach to optimizing dietary protein to growth and body composition in walking catfish, Clarias batrachus (Linneaeus, 1758).

Clarias batrachus is a commercially important food fish. In the present study, effect of varying dietary protein levels was evaluated on the survival, growth parameters and proximate composition of C. batrachus. Diets comprising 25%, 30%, 35%, 40%, 45%, and 50% crude protein (CP) were supplied to fish in T1, T2, T3, T4, T5, and T6, respectively, at the rate of 5% of fish body weight for the entire 90 days, twice daily. Size of each stocked C. batrachus was recorded after 15 days. Results revealed 100% survival rate of C. batrachus in all treatments. Significantly highest (P<0.001) mean value of weight gain (g/fish), percent weight gain, daily growth rate, specific growth rate and protein efficiency ratio (PER) in C. batrachus were recorded, reared in T4 by feeding 40% CP in diet. The best FCR value (1.90±0.02) for C. batrachus was obtained in T4 by feeding 40%CP in diet. Mean value of water, ash, fat and protein contents (wet mass) were ranged 74.10-79.23%, 3.12-4.68%, 3.90-4.43% and 13.09-16.79% for C. batrachus in the studied treatment groups. Water content (%) was found significantly (P<0.05) higher in the body of C. batrachus for T1, T2, T3 and T6 than for T4 and T5. Ash was found significantly (P<0.05) higher in the fish reared in T4 and T5. Fat content in the wet body mass of C. batrachus was found significantly higher in T4 and T1. While, significant higher (P<0.05) values of mean protein content was noted in C. batrachus reared in T4 and T5. Body composition of C. batrachus was also categorically affected by body size, however, condition factor showed non-significant correlation in most of the relationships in the present study. Overall, results indicated that feeding appropriate diet (containing 40% CP) to the fish resulted good growth performance, lower FCR and higher protein content in the fish. Present study provides valuable knowledge of optimal dietary protein level in C. batrachus which will help in commercial success of aquaculture.

Effects of Varying Dietary Protein Levels on Growth Performance, Survival, Body Composition, Haemato-Biochemical Profile, and Metabolic Responses of Hypselobarbus jerdoni (Day, 1870) Juveniles

A 60-day feeding trial has been carried out to access the optimal dietary crude protein (DCP) requirement of juvenile Jerdon’s carp, Hypselobarbus jerdoni. Six isoenergetic (around 400 Kcal DE/100 g), isolipidic (60.80 g/kg), and heteronitrogenous diets were prepared with graded levels of protein, viz., 200, 250, 300, 350, 400, and 450 g/kg (TCP 20-TCP 45 with 50 g/kg incremental level). A completely randomised design (CRD) was used to distribute 270 Jerdon’s carp juveniles (6.12–6.18 g) in six experimental groups in triplicates (15 fish/tank, 200 l water capacity). After 60 days, the fishes of the TCP30 group showed significantly higher weight gain, final body weight, and percentage weight gain (WG%). The fish of the TCP30 group exhibited a significantly higher feed efficiency ratio and specific growth rate. On the other hand, a significantly lower feed conversion ratio is recorded in the TCP30 and TCP35 groups. The protein efficiency ratio of fish was reduced significantly with the elevated DCP level. Whole-body moisture, lipid, and total ash contents of H. jerdoni were remain unaffected by DCP levels. However, DCP levels significantly influenced the whole-body protein of H. jerdoni juveniles, with significantly higher values noticed in the TCP30 and TCP35 groups. The TCP35, TCP40, and TCP45 groups exhibited significantly higher (p&lt;0.05) protease activity, and the amylase activity showed a decreasing trend in response to dietary protein levels. A significantly (p&lt;0.05) higher SOD and CAT activity were observed in the TCP20 and TCP25 groups. However, lower hepatic glutamate pyruvate transaminase and glutamic-oxaloacetic transaminase activity were observed in the TCP30 and TCP35 groups, respectively. Furthermore, based on broken-line linear and second-order polynomial regression with respect to WG%, the optimal dietary crude protein requirement of H. jerdoni cultured for 60 days was found to be 309.72 and 316.40 g/kg.

An estimation of optimum dietary concentration of soy bean meal for carps (Catla catla, Labeo rohita and Cirhinus mrigala).

Soybean meal is an inexpensive plant origin protein which has been used in practical diets as a replacement of animal protein such as fish meal or chicken meal, due to the uneconomical price of animal protein diets. Consequently, a research study was conducted on some commercial species of Indian major carps i.e. Catla (Cattla cattla), Rohu (Labeo rohita) and Mrigala (Cirhinus mrigala) (Hamilton, 1822) to estimate optimum dietary protein requirement of soy bean meal in diet in an intensive polyculture. Three different diets (SBM I, SBM II and SBM III) were formulated by 80%, 50% and 20% replacement of fish meal with soybean meal from a 45% fish meal diet (control).Highest monthly mean weight gain was obtained by SBM II (with 35% CP and about 50% substitution of fish meal), while SBM III (45% Crude Protein and about 20% substitution of fish meal) was stood second. All tested diets respond enormously by producing high yield as compare to control diet, though SBM II generated highest yield among all. On the bases of the following research, it was revealed that the SBM can surrogate even50% fish meal without any augmentation of other amino acids in the diet of Indian major carps.

Do optimum dietary protein and early mild stress events prepare oscar (Astronotus ocellatus) for a stressful future?

This study aimed to investigate the effects of dietary protein (380 vs 510 g/kg) and duration of early mild stress (0, 2 and 4 weeks) on growth, haematology, serum biochemistry, immunological response, antioxidant system, liver enzymes, and stress responsiveness of oscar (Astronotus ocellatus; 4.7 ± 0.6 g). After the nine-week feeding trial, all fish were exposed to final acute AC stress (acute confinement stress) and sampled for serum and haematological parameters. Fish fed dietary 510 g/kg protein grew faster (gain 54.21 g vs 42.98 g) and had a higher condition factor (2.22 vs 1.81) than those fed diets containing 380 g/kg protein after ten weeks feeding ad libitum. After AC stress, oscars subjected to four-time stress (4EMS) had a higher survival rate than the 0EMS group (77.08% vs 64.59%). Additionally, white blood cells, blood performance, total protein, high-density lipoproteins, immunoglobulin M, complement component 4, complement component 3, superoxide dismutase, and glutathione peroxidase were significantly greater in the two-time stress (2EMS) group than the 0EMS treatments. Although fish welfare must be considered, mild stress during the trial can reduce glucocorticoid feedback sensitivity in fish, resulting in greater survival after the acute stress reaction at the end of the study.

Optimal dietary protein level for the growth and metamorphosis of bullfrog (Lithobates catesbeianus) tadpoles

This study investigated the effects of dietary protein levels on growth performance, antioxidant capacity, digestive enzyme activity, and metamorphosis rate of the bullfrog (Lithobates catesbeianus) tadpoles. Seven isolipidic and isoenergetic diets were formulated with 24.61%, 28.49%, 33.74%, 37.50%, 44.06%, 48.39% and 53.92% crude protein. Triplicate replicates of tadpoles (growth stage 25 and 0.009 g) were fed with experimental diets two times daily for 11 weeks, and the daily feeding amount was 6.50% of the tadpole's body weight. Weight gain (WG), specific growth rate (SGR), the total antioxidant capacity (T-AOC) and catalase (CAT) activity in the liver, the intestinal trypsin activity (TPS) and metamorphosis rate at stage 42 of bullfrog tadpoles all increased with increasing dietary protein level from 24.61% to 44.06% and then decreased. Based on the second-order polynomial regression analysis of the weight gain and metamorphosis rate at stage 41 vs. dietary protein level, the optimal dietary protein level for bullfrog tadpoles was 42.49% and 46.50%, respectively. In conclusion, the optimum dietary protein level of bullfrog tadpoles was estimated to be 42.49%–46.50% of the diet.

Reassessment of dietary protein and lipid requirements for large yellow croaker, Larimichthys crocea, reared in net pens

AbstractAt present, large yellow croaker, Larimichthys crocea, a carnivorous fish ranked fifth in aquaculture production among marine finfishes in the world, still relies on raw fish diet because formulated feed alone is not able to sustain rapid growth of the fish. The present study evaluated growth, feed utilization efficiency, body composition and antioxidant capacity of large yellow croaker fed diets containing four protein (430, 460, 490 and 520 g/kg) and three lipid (60, 90 and 120 g/kg) levels. Fish weighing 11.4 ± 2.8 g were fed with the test diets in net pens for 8 weeks. Final body weight and nitrogen retention efficiency (NRE) were dependent on dietary protein and lipid levels and their interaction. Weight gain, body protein content, serum catalase (CAT) activity and liver glutathione peroxidase (GSH‐Px) activity were dependent on dietary protein and lipid levels. Phosphorus retention efficiency was dependent on dietary protein level and interaction between protein and lipid levels. Hepatosomatic index, body lipid and energy contents, activities of superoxide dismutase (SOD) and GSH‐Px in serum, and CAT activity and malondialdehyde content in liver were dependent on dietary lipid level. The final body weight and weight gain of fish fed at 490 g/kg protein level did not significantly differ from those fed at 520 g/kg protein level. The final body weight, weight gain and NRE of fish fed at 90 g/kg lipid level were higher than those fed at 60 g/kg lipid level, but did not significantly differ from those fed at 120 g/kg lipid level. The maximum weight gain occurred in fish fed the diets either containing 520 g/kg protein or 90 g/kg lipid. The body lipid content, as well as SOD and GSH‐Px activities in serum, were higher in fish fed the diets with 90 and 120 g/kg lipid compared to fish fed the diets with 60 g/kg lipid. The present study reveals that the optimal dietary protein and lipid levels for large yellow croaker reared in net pens were 490–520 g/kg and 90 g/kg, respectively.

Optimal dietary energy and protein levels for breeding pigeons in the winter "2 + 3" lactation pattern

The nutritional requirements of breeding pigeons depend on their physiological period, breeding pattern, and environmental conditions. Despite works on reduced litter size in winter production to combat high mortality and the poor welfare of squabs, there are few studies on the related nutritional requirements of these pigeons. A total of 432 pairs of European Mimas pigeons were randomly divided into 9 groups in which 3 crude protein (CP) levels (15, 16.5, and 18%) and 3 metabolizable energy (ME) levels (12.2 MJ/kg, 12.4 MJ/kg, and 12.6 MJ/kg) were tested to determine the optimal energy and protein requirements of breeding pigeons in the winter "2+3" breeding pattern. The results showed that ME and CP levels had little effect on the body weight, feed intake, and egg quality of breeding pigeons during the lactation period. An 18% CP diet significantly increased the laying rate and hatchability (P < 0.05), but there was no difference in the laying rate with 18% CP and 16.5% CP during the whole reproductive cycle (P > 0.05). There was a significant interaction between ME and CP levels, and the laying interval of breeding pigeons in group 9 (18% CP; 12.6 MJ/kg) was significantly shortened (P < 0.05). For squabs, the ME level had no effect on growth performance, slaughter performance, or meat quality. The body weight of 21-day-old squabs in the 18% CP group increased by 3.16% compared with that of the 15% CP group, but there was no difference between the 18% CP and 16.5% CP groups. Compared with other experimental groups, group 7 (18% CP; 12.2 MJ/kg) had the fastest growth rate in squabs (P < 0.05), and the corresponding slaughter weight was also the heaviest (P < 0.05). We further found that the height of the squab intestinal epithelium was significantly increased in both the 16.5% CP and 18% CP groups of squabs (P < 0.01), but male breeding pigeons showed a certain degree of oxidative stress with an increase in CP level. In conclusion, the effects of 15 to 18% CP levels and 12.2 to 12.6 MJ/kg ME levels on the reproductive metabolism of breeding pigeons and the growth and development of squabs in the "2+3" breeding pattern during winter are small. For economic efficiency, we suggest that the CP level can be reduced to 16.5% while the ME level should not be less than 12.2 MJ/kg in practical production.

Evaluation of optimal dietary protein levels and meat quality of adult hybrid abalone (Haliotis discus hannai♀ × H. fulgens♂) under two representative water temperatures

In this study, the optimal dietary protein levels for adult hybrid abalone (H. discus hannai♀ × H. fulgens♂) were evaluated at two representative temperatures, and the interactive influences of dietary protein and water temperature on abalone meat quality were examined. Six isoenergetic and isolipidic diets containing graded levels of protein (15%, 20%, 25%, 30%, 35%, and 40%) were fed to the hybrid abalone for 90 days. Based on the specific growth rate, the optimum dietary protein levels for adult hybrid abalone using a quadratic curve model were estimated to be 28.07% and 26.47% of the diet at 23 °C (optimum temperature) and 27 °C (high temperature), respectively. The amount of crude protein in the abalone body increased linearly with the dietary protein levels and water temperature. Antioxidation enzyme activities of abalone muscle, including GPx and GST were significantly affected by the interaction of dietary protein levels and water temperature. As for texture analysis, the abalone kept at 23 °C exhibited higher meat hardness than those fed the same diets at 27 °C. The n-3 PUFAs (particularly DHA and EPA) in abalone meat were significantly influenced by dietary protein levels, and the highest content was observed in the 30% dietary protein group. These levels were not affected by water temperature. In addition, higher dietary protein levels and water temperatures increased the total contents of free amino acids and flavor amino acids (Asp + Glu + Gly + Ala + Arg + Tau). The cooking loss of abalone meat was reduced with increased protein levels and was significantly lower in the 23 °C group, along with a higher meat postmortem pH value. The collagen fiber ratio and collagen content of abalone meat were higher in the 23 °C group. In summary, for multiple diet feeding strategies in practical production of abalone aquaculture, the balance between the seasonally specific feeds cost benefits and the abalone meat quality should be carefully evaluated.

The Requirement and Protective Effects of Dietary Protein against Chronic Ammonia Exposure in Juvenile Genetically Improved Farmed Tilapia (Oreochromis niloticus).

Ammonia is a key risk factor in intensive aquaculture systems. This experiment is aimed at investigating the influence of dietary protein levels on genetically improved farmed tilapia (GIFT, Oreochromis niloticus) under chronic ammonia stress. GIFT juveniles of 4.00 ± 0.55 g were exposed to high ammonia level at 0.88 mg/L and fed with six diets comprising graded protein levels at 22.64%, 27.26%, 31.04%, 35.63%, 38.47%, and 42.66% for 8 weeks. The fish in negative control was fed the diet with 31.04% protein in normal water (0.02 mg ammonia/L water). Our results showed that high ammonia exposure (0.88 mg/L) caused significant decrease in fish growth performance, hematological parameters, liver antioxidant enzymes (catalase and glutathione peroxidase), and gill Na+- and K+-dependent adenosine triphosphatase (Na+/K+-ATP) activity. When fish were under high ammonia exposure, the weight gain rate, special growth rate, feed efficiency, and survival rate elevated significantly with dietary protein supplementation increase to 35.63%, whereas protein efficiency ratio, hepatosomatic index, and viscerosomatic index showed a decreased tendency. Dietary protein administration significantly enhanced crude protein but reduced crude lipid contents in the whole fish. Fish fed diets with 35.63%-42.66% protein had higher red blood cell counts and hematocrit percentage than fish fed 22.64% protein diet. The values of serum biochemical indices (lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase), hepatic antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), and gill Na+/K+-ATP activity were all elevated with the increment of dietary protein. Moreover, histological analysis indicated that dietary protein administration could prevent the ammonia-induced damages in fish gill, kidney, and liver tissues. Based on weight gain rate as a response criterion, the optimal dietary protein requirement for GIFT juveniles under chronic ammonia stress was 37.9%.

Insulin-like growth factor II, a marker gene for determining the optimum dietary protein level in clownfish Amphiprion ocellaris.

In vivo study was conducted to determine the role of insulin-like growth factors (IGF-II) related to dietary protein utilization. For this early juvenile stage of marine false clownfish Amphiprion ocellaris, 300 numbers of 20-day-old larvae (initial body weight of 18.2±0.027 mg/fish) were used as an experimental animal. Animals were fed for 12 weeks with different dietary protein levels (35, 40, 45, 50, and 55%), using Spirulina maxima as a major protein source. Proximate compositions and amino acid profile of the formulated diet were analyzed by the standard methods. Eventually, significant (P<0.05) mean, body weight gain, absolute growth rate, specific growth rate, and feed conversion ratio were obtained in the fishes fed with 50% of dietary protein, whereas, poor growth performance was noticed in 35% of the dietary protein level fed juveniles. The growth-responsible gene IGF-II expression studies showed the significant upregulation in the growth of the juveniles at 2.05±0.11 for 40%, 3.13±0.20 for 45%, 4.97±0.13 for 50%, and 4.33± 0.24 for 55%, which were higher than the control group 35%. The study concluded that 50% of dietary protein level is optimal for better growth indices in clownfish; A. ocellaris juveniles and IGF-II can be used as a potential marker gene to assess the growth indices in A. ocellaris.

Effects of Different Dietary Protein Levels on the Growth Performance, Physicochemical Indexes, Quality, and Molecular Expression of Yellow River Carp (Cyprinus carpio haematopterus)

A 12-week rearing trial was carried out to estimate effects on the growth performance, physicochemical indexes, quality, and the molecular expression of Yellow River Carp (Cyprinus carpio haematopterus) using five practical diets, including dietary protein levels of 220, 250, 280, 310, and 340 g/kg. The results illustrated that the fish's weight gain (WG) and specific growth rate (SGR) were significantly influenced, with an ascending dietary protein level of up to 250 g/kg (p < 0.05). The carp muscle contents of total saturated fatty acids (∑SFA), monounsaturated fatty acids (∑MUFA), polyunsaturated fatty acids (∑PUFA), and fatty acids (∑FA) decreased significantly with the ascending dietary protein levels, except for the 250 g/kg protein diet (p < 0.05). Only the glutamic acid and total essential amino acid (∑EAA) contents were significantly influenced by the ascending dietary protein levels (p < 0.05). The relative GH expression of the carp muscle significantly decreased with the increase in the dietary protein level up to 310 g/kg, and then it significantly increased (p < 0.05). In the intestines, the peak relative TOR expression was observed on the 220 g/kg protein diet, while the relative 4EBP1 expression was significantly influenced by the dietary protein level up to 250 g/kg (p < 0.05). In the muscle, the peak relative TOR and 4EBP1 expression levels were observed on the 250 g/kg protein diet. In gills, the lowest relative Rhag, Rhbg, and Rhcg1 expression levels were observed on the 250 g/kg protein diet. Based on all of the aforementioned results, the optimal dietary protein level for Cyprinus carpio haematopterus (160.24 ± 15.56 g) is 250-280 g/kg.

Dietary Protein Requirement of Juvenile Dotted Gizzard Shad Konosirus punctatus Based on the Variation of Fish Meal.

An 8-week feeding trial was conducted to investigate the effects of dietary protein levels on growth performance, feed utilization, and energy retention of juvenile dotted gizzard shad Konosirus punctatus based on the variation of fish meal. Fish meal was used as the sole protein source; five semi-purified diets were formulated with varying crude protein (CP) levels of 22.52%, 28.69%, 34.85%, 38.84%, 45.78% (CP1-CP5 diets). A total of 300 uniform juveniles with initial body weight 3.61 ± 0.20 g fish-1 were randomly divided into five groups with three replicates in each group. The results showed that different CP levels did not significantly affect the survival of juvenile K. punctatus (p > 0.05). The values of weight gain (WG) and specific growth ratio (SGR) showed a general enhancing trend and then weakened with increasing dietary CP levels (p > 0.05). Feed utilization also improved with increasing dietary CP levels (p > 0.05), and the optimal feed conversion ratio (FCR) value was found in fish fed the diet with CP3 (p > 0.05). The rise of dietary CP from 22.52% to 45.78% enhanced the daily feed intake (DFI) and protein efficiency ratio (PER) values of K. punctatus (p < 0.05). With the increase of dietary CP levels, daily nitrogen intake (DNI), energy retention (ER), and lipid retention (LR) elevated, while retention (NR), daily energy intake (DEI), and daily lipid intake (DLI) reduced (p < 0.05). No statistical differences in the content of water, crude protein, and crude lipid were observed among different treatments (p > 0.05). The activity of lipase in CP3 and CP4 diets was significantly higher than that of the CP1 diet (p < 0.05). Fish fed CP2 and CP3 diets had significantly higher amylase activity than that of the CP5 diet (p < 0.05). The levels of alanine aminotransferase (GPT) first enhanced and then decreased as dietary CP levels raised. The second-order polynomial regression model analysis of the WG and FCR indicated that the optimal dietary protein level for K. punctatus is about 31.75-33.82% based on the variation of fish meal.

Optimal Dietary Protein Requirement of Subadult Australian Hybrid Abalone (Haliotis rubra × Haliotis laevigata) at Different Rearing Temperatures

Australian abalone aquaculture is characterised by a prolonged culture period and slow and variable growth, and abalone is cultured in fluctuating water temperatures ranging between 10 and 25°C with distinct seasons. Temperature is a crucial environmental factor influencing abalone’s physiology and energetics, leading to a change in nutritional requirements. However, feeds are generally formulated to match the nutritional requirements at their optimal temperature. Hence, there is a need to optimise dietary protein levels to match temperature-specific requirements during extreme conditions (winter and summer). Given this, a growth trial evaluating five experimental feeds consisting of graded protein inclusion levels (320, 350, 380, 410, and 440 g·kg−1) was conducted on subadult hybrid abalone (Haliotis rubra × H. laevigata) at three different temperatures reflecting winter (12°C), summer (22°C), and the annual average water temperature (17°C) for 143 days. At lower water temperature (12°C), there was a marginal improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1. However, at higher water temperatures (when the culture water temperature is above 17°C), there was a significant improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1 as evidenced by an improved weight gain, specific growth rate, and feed conversion ratio. Furthermore, increasing dietary protein levels did not compromise the nutritional quality of the abalone tissue at all three tested temperatures. Therefore, during periods of higher water temperatures, feeding Australian hybrid abalone with a relatively high dietary protein level (410 g·kg−1) is expected to result in improved growth, shorter culture duration, and profit maximisation.

Optimal dietary protein to carbohydrate ratio for black soldier fly (Hermetia illucens) larvae

Black soldier fly (Hermetia illucens, BSF) larvae can utilise biowaste streams and convert them into high-quality larval biomass. However, the nutritional requirements of BSF larvae are largely unknown and remain to be identified to optimally use biowaste streams for BSF rearing. The current study thus investigated the optimal dietary protein to carbohydrate ratio for industrially reared BSF larvae for food and feed applications. In addition to a chicken feed control with a crude protein to non-fibre carbohydrate ratio (P:C) of 1:3, six isoenergetic and isolipidic experimental substrates were formulated with the P:C ratios ranging between 1:1 – 1:9. Each substrate was fed to triplicate groups of 5-days old larvae (n=10,000 per box) reared under commercial scale conditions for 11 days before harvesting. Highest overall performance was observed for larvae reared on substrates with P:C ratios between 1:2 – 1:3, corresponding to protein to energy ratios (P:E) of 11.2-14.4 g/MJ. Larvae reared on these substrates had the highest final yield, highest survival, and the lowest feed conversion ratio. Feeding the most protein-biased substrates (P:C ratios of 1:1 – 1:1.5) or the most carbohydrate-biased substrate (P:C ratio of 1:9) significantly lowered larval survival. Additionally, larvae fed a more carbohydrate-biased substrate resulted in a prolonged development time. In summary, the study found that P:C ratios of 1:2 – 1:3 (11.2-14.4 g/MJ P:E) were most optimal in terms of obtaining the highest larval yield and ensuring the best utilisation of feed resources for BSF production while meeting larval macro-nutritional requirements.