Optimum Dietary Protein Research Articles

Optimal Dietary Protein and Lipid Levels for Juvenile Yellowstripe Goby (Mugilogobius Chulae), a Proposed Laboratory Fish

Mugilogobius chulae is a small euryhaline or estuarine goby recently proposed as an ideal species for use in ocean environmental toxicology studies. However, the nutritional requirements of M. chulae remain unknown. Eight experimental diets at one of four protein levels (35%, 40%, 45%, or 50%) and two lipid levels (5% or 10%) were formulated to investigate the effects of differing dietary protein and lipid levels on the growth performance, body composition and liver morphological condition of M. chulae. Juvenile gobies (1760 individuals, 0.011±0.001 g fish-1) were randomly allotted to 32 tanks (four replicates of each of the eight treatments) and fed twice a day for 9 weeks. Weight gain (WG) and specific growth rate (SGR) increased significantly with increasing dietary protein from 35% to 45% (P 0.05). Whole-body crude lipid and linoleic acid (C18:2n-6) contents in juvenile M. chulae increased significantly with increasing dietary lipid content (P 0.05), and no pathological changes were observed in the liver, lipase activity significantly decreased (P < 0.05). The dietary protein level driving optimal WG and SGR also led to the highest trypsase activity. Thus, 45% crude protein and 5% lipidis sufficient to ensure good growth performance in juvenile M. chulae, and this diet appears to have no substantial adverse effects.

Digestible Protein Requirement of Pirarucu Juveniles (Arapaima gigas) Reared in Outdoor Aquaculture

Pirarucu (Arapaima gigas) is a fast-growing, carnivorous species reared commercially in Amazonian countries as Brazil. Lack of a nutritionally balanced and affordable diet is a major constraint in pirarucu aquaculture, and our investigation sought to estimate the dietary protein requirement for this species. Four diets were formulated to contain increasing concentrations of digestible protein (32, 35, 38, and 41%) and fed to triplicate groups of juvenile pirarucu of around 2 kg for 18 weeks. As result, pirarucu showed no differences in feed intake, survival, or fillet yield. However, regression analysis revealed that weight gain (WG) values showed a general increasing trend with increasing dietary digestible protein (DP) level up to 36.7%. In addition, feed conversion rates were also improved with increase in dietary DP up to 36.4%. Fish fed diets containing 32 and 41% had poor feed conversion rates. Thel protein retention rate (PRR) and protein efficiency index (PER) decreased as levels of DP increased. The optimal dietary protein content for juvenile pirarucu between 1.98 and 4 kg of BW is about 36% of digestible protein on diet.

Effects of increasing protein level on the performance, enzyme activity and body composition of the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879)

A six-week growth trial was performed to estimate the dietary protein requirements for maximum growth of juvenile Brazilian sardine (Sardinella brasiliensis) based on growth performance, feed utilization, body composition and digestive enzyme activity. Six isoenergetic diets were formulated to contain protein levels that increased from 250 to 500 g/kg. Each diet was randomly assigned to triplicate groups of 160 fish with mean initial body weight of 0.93 ± 0.13 g, which were fed four times a day to apparent satiation. Growth tended to increase with the increase in the dietary protein level up to 400 g/kg. Total protein intake was indirectly correlated to apparent protein utilization. No significant differences in whole-body composition were found between fish fed the different protein levels. Acid protease and neutral lipase activities did not show significant differences among the different protein dietary groups. Alkaline protease activity increased in fish fed up to 350 g/kg of protein and amylase activity in fish fed up to 400 g/kg. Using polynomial regression, 367 g/kg was estimated to be the optimum dietary protein requirement for maximum weight gain of juvenile Brazilian sardines.

Effects of dietary protein and lipid levels on growth, feed utilization and body composition in juvenile goldfish, Carassius auratu

An 8-week feeding trial was conducted to determine the optimum dietary protein and lipid levels for growth, feed utilization and body composition of goldfish, Carassius auratus juveniles (1.66 ± 0.018 g). Six diets containing two protein levels (300 and 400 g/kg) and three lipid levels (40, 80 and 120 g/kg) were formulated. Fifteen fish were randomly allotted to 18 aquaria (0.6 × 0.3 × 0.45 m) and fed to apparent satiation. The results showed that weight gain and specific growth rate (SGR) increased in response to higher dietary proteins with highest weight gain and SGR recorded in diet containing 400 g/kg protein with 80 g/kg lipid. Both feed intake (FI) and protein efficiency ratio (PER) were dependent on dietary protein and lipid level (P less than 0.05). Lipid retention (LR) was negatively correlated while hepatosomatic index (HSI) and viscerosomatic index (VSI) was positively correlated with dietary lipid levels. Whole body protein content decreased (P less than 0.05) while, lipid content increased with increasing dietary lipid at each protein level. Second-order polynomial regression also revealed diet containing 400 g/kg protein level and 80 g/kg lipid level optimal for the growth and feed utilization of juvenile goldfish, C. auratus.

Effect of dietary protein and protein energy ratio on the growth performance of lemon fin barb hybrid (Hypsibarbus wetmorei X Puntius gonionotus) larvae

This study was carried out to determine basic requirement of larval Lemon Fin Barb hybrid. There were three experiments in this study. The first experiment is considered as preliminary experiment. The objective is to measure the mouth gape of the larvae. This was done in order to get the right particle size of formulated diet that will be utilized in experiment protein and protein energy ratio requirement of the larvae. The newly hatched larvae were collected from Aquaculture Extension Research Center, Perlok, Pahang, Malaysia. The feeding trial was done in twenty-one days by feeding the larvae with frozen crushed Artemia due to its small mouth gape size than size of Artemia nauplii which ranged from two hundred to four hundred micron. The mouth of larvae opened at the third day after hatched with 49 micrometer mouth gape at 45 degrees. Size of frozen crushed Artemia was 40.93 ± 4.12 micrometer. This size fit well with the mouth gape size of the larvae since day three after hatched. By referring to results obtained in mouth gape study, in subsequent protein and protein energy ratio studies, formulated diet was sieved with 50 micrometer sieve on third day after hatched, on thirteen day after hatched formulated diet was sieved with 100 micrometer sieve and on seventeen day after hatched onwards formulated diet was sieved with 150 micrometer sieve. A series of two experiments were conducted to study the optimum dietary protein level and protein to energy ratio of Lemon Fin Barb hybrid larvae. In experiment one, five formulated diets (4700 kilocalorie per kilogram) ranging from forty to sixty percents protein in five percents increments were fed for twenty-one days to triplicate groups of Lemon Fin Barb hybrid larvae (initial weight: 1.62 ± 0.03 miligram per fish). Larvae were weaned into formulated diet on day six after hatched. From day three to day five after hatched larvae were fed with frozen crushed Artemia in order to develop gustatory response to the digestive system of the larvae. Sampling was done at four days interval. Data on weight, length and survival were taken during sampling process. Weight gain of fish was proportional to the protein content of the diet up to an incorporation rate of fifty percents. Among formulated diets, diet with fifty percents protein recorded the highest weight gain (39.03 ± 0.71 miligram). The dietary protein level that yielded maximum growth was forty-nine percents based on a broken-line model estimation of weight gain. Due to this result, two dietary protein levels (45 percents and 50 percents) were used along with four energy levels at each protein level (4500, 4700, 4900 and 5100 kilocalorie per kilogram diet) in experiment two. In experiment two, eight diets were formulated consisting of protein level (45 percents and 50 percents) with energy level (4500, 4700, 4900 and 5100 kilocalorie per kilogram diet). The survival of fish fed diets containing 45 percents protein was significantly lower (P<0.05) than that of fish fed diets containing 50 percents protein regardless of energy level. Weight gain of fish was significantly (P<0.05) different at all dietary protein and energy levels. The best growth was observed in larvae fed diet 7 containing 50 percents protein with 4900 kilocalorie per kilogram energy with the highest weight gain (43.80 ± 0.64 miligram), best feed conversion ratio (1.05 ± 0.04) and protein energy ratio of 99.36 miligram per kilocalorie. In conclusion Lemon Fin Barb hybrid larvae started opening mouth on third day after hatched at 49 micrometer mouth gape at 45 degrees. The optimum protein level in diet for this new hybrid is fifty percents while the optimum energy is 4900 kilocalorie per kilogram with protein energy ratio of 99.36 miligram per kilocalorie.

Optimum Dietary Protein and Lipid Levels in Juvenile Filefish, Stephanolepis cirrhifer, Feed

AbstractA feeding trial was designed to assess the effects of dietary protein and lipid content on growth, feed utilization efficiency, body composition, and hematological indices of juvenile filefish, Stephanolepis cirrhifer. Eight experimental diets were formulated with a combination of four protein (35, 40, 45, and 50%) and two dietary lipid levels (7 and 14%). Each diet was fed to triplicate groups of fish (3.2 ± 0.06 g) to apparent satiation for 8 wk. Fish growth performance and feed utilization were significantly affected by increasing dietary protein and lipid levels, with no significant interactions between factors. The highest growth performance value, in terms of weight gain, was observed in groups fed the diets with 50% protein (399%). However, fish fed the diet containing 45% protein had comparable growth (357%) while achieving relatively higher protein efficiency ratio. Hepatosomatic index was significantly affected by interaction of dietary lipid and protein with the highest values observed in those fish fed the highest protein (45–50%) and lipid (14%) diets. There was a significant increase in body lipid content (5.1 to 6.6%) and a decrease in body protein (15.8 to 14.8%) and ash (2.47 to 2.16%) with increasing dietary lipid levels from 7 to 14%. Muscle lipid content was significantly affected by both dietary protein and lipid levels and tended to increase with increasing dietary protein and lipid levels, ranging from 0.13 to 1.20%. Liver lipid content (65.9 to 68.7%) was significantly increased with the increase in dietary lipid levels while liver moisture content (28.9 to 25.9%) showed a clear decreasing trend. Hematological values were also altered with the increase in either dietary protein or lipid levels. These findings may suggest that a diet containing 45% protein and 7% lipid, with a protein to energy ratio of 23.8 mg/kJ, could deliver sufficient nutrient and energy to support acceptable growth and feed utilization and avoid excessive fat deposition in juvenile filefish.

Influence of dietary protein/lipid ratio on growth performance and body composition of Aspikutum, a new hybrid of Leuciscus aspius ♀ × Rutilus frisii ♂ (Teleostei: Cyprinidae)

A 3×2 factorial experiment with six trial diets containing three protein levels (30, 35 and 40%) and two lipid levels (10 and 15%) was conducted to investigate the optimum dietary protein to lipid ratio of Aspikutum, Leuciscus aspius ♀ × Rutilus frisii ♂. In this experiment, 252 fish (31.22±0.38g; mean±SE) were stocked in 18 tanks with the volume of 400L and were fed 3 times daily for 60 days. The results indicated that growth performance and feed conversion ratio was significantly affected by protein content of the diet, so that these parameters increased significantly with increasing protein level from 30% to 35%, and then decreased in 40%. Protein efficiency ratio and hepatosomatic index decreased with increasing dietary protein level. Lipid efficiency ratio decreased with increasing dietary lipid level. Lipid content of carcass was decreased with increasing the dietary protein, so that the highest amount of lipid was observed in fish fed by 30% protein and 15% lipid. Also, body moisture of fish fed by 40% protein and 15% lipid was higher than those of other treatments. In general, the results indicated that diet containing 35% protein and 15% lipid is suitable for the optimum growth and feed utilization of Aspikutum in juvenile stage.

Adequate dietary protein level enhances stress resistance and immune status of blunt snout bream (Megalobrama amblycephalaYih, 1955)

This study hypothesized that an optimum dietary protein level might play an important role in improving stress tolerance, enhancing an immune function, and ultimately minimizing temperature stress. For this purpose, the present study conducted a 10-week feeding trial followed by a 7-day stress experiment to evaluate the effects of dietary protein levels (28%–36%) on the physiological performances and hepatic Hsp70 gene expression in blunt snout bream Megalobrama amblycephala fry under a high temperature challenge. Fish fry (initial weight, 16.08 ± 0.03 g, n = 25) were fed with their respective diets to apparent satiation, and samples taken once before stress and four times during high temperature stress days (0.125, 0.5, 2 and 7 days). Serum total protein and cholesterol contents before stress were affected by dietary protein levels; during stress these parameters showed no significant changes up until day 2, showing some changes thereafter. Regardless of 0.125, 0.5, 2 or 7 days during stress, cortisol and aspartate aminotransferase levels in the group fed 32% dietary protein were significantly lower than in the other groups. At 0.125, 0.5 or 2 days during stress, the complement component 3 (C3) and 4 (C4) levels increased significantly up to certain levels, declining thereafter. The expression level of Hsp70 mRNA before stress was not affected by dietary protein levels, but increased significantly from 0.125 to 0.5 days during stress, and was reduced thereafter. Overall, low cortisol and high C3, C4 and Hsp70 mRNA levels were found in the group fed 32% protein throughout the stress experiment, which indicated that an adequate protein level enhances stress resistance and immunity in fish.

Optimal dietary protein level and protein to energy ratio for hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) juveniles

Two consecutive growth trials were undertaken to study optimal dietary protein level and protein to energy ratio of hybrid grouper (Epinephelus fuscoguttatus ♀×Epinephelus lanceolatus ♂) juveniles. In the first trial (trial 1), seven isolipidic and isoenergetic experimental diets were formulated to contain 38%, 42%, 46%, 50%, 54%, 58%, or 62% dietary crude protein (CP) level (dry-matter basis), being abbreviated as P38, P42, P46, P50, P54, P58 and P62, respectively. Each diet was given to triplicate groups (initial average body weight, 3.58±0.05g/fish) for 7weeks. Weight gain (WG%) of fish fed with P38 and P42 were significantly lower (P<0.05) than fish fed with P46, P50, P54, P58 or P62. Fish fed with P46 had significantly lower WG% than fish fed with P62. Fish fed with P38 exhibited significantly higher feed conversion ratio (FCR) than fish fed with P46, P50, P54, P58 or P62. Based on the quadratic regression model at 95% of maximum response of WG%, optimal dietary protein level of hybrid grouper juveniles was estimated to be 53.5% of dry matter. In trial 2, the other seven isonitrogenous (53.5% of dry matter) experimental diets were formulated to contain various dietary protein/energy ratios of 191, 173, 157, 145, 134, 124 and 116mg/kcal (P/E191, P/E173, P/E157, P/E145, P/E134, P/E124 and P/E116), respectively. Each diet of trial 2 was given to triplicate groups (initial average body weight, 10.98±0.15g/fish) for 8weeks. WG% of fish fed the diet with P/E191 was significantly lower than that of fish fed the diet with P/E173 or P/E157, and there were no significant differences in WG% values among fish fed diets with P/E191, P/E145, P/E134, P/E124 and P/E116. Values of DFI of fish fed P/E191 and P/E173 were significantly higher than those of fish fed P/E134, P/E124 and P/E116. Fish fed P/E191 exhibited significantly higher FCR than fish fed P/E157, P/E145, P/E134, P/E124 or P/E116, and fish fed P/E173 showed significantly higher FCR than fish fed P/E124 or P/E116. IPF together with lipid contents of whole-body and liver were increased as dietary P/E ratio decreased. Results of trial 2 indicated that dietary P/E ratio of 157mg/kcal was optimal for hybrid grouper juveniles.

Protein/amino-acid modulation of bone cell function.

Nutrients (protein, carbohydrates and fats) have traditionally been thought of as fuels simply providing the energy for cellular metabolic activity. According to the classic view, if nutrients are available, then anabolic pathways are activated, and if nutrients are not available, catabolic pathways are activated. However, it is becoming increasingly clear that nutrient effects on bone cells (stem cells, osteoblasts and osteoclasts) are complex, some nutrients promote bone formation, whereas others interfere with bone formation or actually promote bone break down. At an organ level, nutrient intake can suppress bone breakdown and modulate the activity of the calcium/vitamin D/parathyroid hormone axis. At a cellular level, nutrient intake can impact cellular energetics either through a direct mechanism (binding or uptake of the nutrient into the cell) or indirect (by elevating nutrient-related hormones such as insulin, insulin-like growth factor 1 or incretin hormones). It is also becoming clear that within a nutrient class (for example, protein), individual components (that is, amino acids) can have markedly different effects on cell function and impact bone formation. The focus of this review will be on one nutrient class in particular, dietary protein. As the prevalence of inadequate dietary protein intake increases with age, these findings may have translational implications as to the optimal dietary protein content in the setting of age-associated bone loss.

Effects of dietary protein levels on growth performance and body composition of juvenile parrot fish, Oplegnathus fasciatus

The present study was conducted to evaluate the effects of dietary protein levels on growth, biometrics, hematology and body composition in juvenile parrot fish Oplegnathus fasciatus. Fish averaging 7.1 ± 0.06 g (mean ± SD) was randomly distributed into 15 net cages (each size: 60 × 40 × 90 cm, W × L × H) as groups of 20 fish. Five isocaloric diets (16.7 kJ/g energy) were formulated to contain crude protein levels (CP) as 35 (CP35), 40 (CP40), 45 (CP45), 50 (CP50) and 60 % (CP60) in the diets. Fish were fed one of the experimental diets at apparent satiation twice a day in triplicate groups. At the end of 8-week feeding trial, weight gain (WG) of fish fed with CP50 and CP60 diets were significantly higher than those of fish fed with CP35, CP40 and CP45 diets. Fish fed with CP45, CP50 and CP60 diets had higher feed efficiency (FE) and specific growth rate (SGR) than those of fish fed with CP35 and CP40 diets. Protein retention efficiency (PRE) decreased with increase of dietary protein levels among fish fed with the experimental diets. Whole-body crude protein and lipid contents increased with the dietary protein level up to CP50 diet. In conclusion, analysis of variance (ANOVA) revealed that the optimum dietary protein level could be 50 % for maximum growth of juvenile parrot fish, while the broken-line analysis of WG suggested that the level could be 48.5 %, in a diet containing 16.7 kJ/g energy.

Re-evaluation of the optimum dietary protein level for maximum growth of juvenile barred knifejaw Oplegnathus fasciatus reared in cages

We determined the optimum dietary protein level in juvenile barred knifejaw Oplegnathus fasciatus in cages. Five semi-purified isocaloric diets were formulated with white fish meal and casein-based diets to contain 35, 40, 45, 50, and 60 % crude protein (CP). Fish with an initial body weight of 7.1 ± 0.06 g (mean ± SD) were randomly distributed into 15 net cages (each size: 60 cm × 40 cm × 90 cm, W × L × H) as groups of 20 fish in triplicates. The fish were fed at apparent satiation level twice a day. After 8 weeks of feeding, the weight gain (WG) of fish fed 45, 50, and 60 % CP diets were significantly higher than those of fish fed 35 and 40 % CP diets. However, there were no significant differences in WG among fish fed 45, 50, and 60 % CP diets. Generally, feed efficiency (FE) and specific growth rate (SGR) showed a similar trend as WG. However, the protein efficiency ratio (PER) was inversely related to dietary protein levels. Energy retention efficiency increased with the increase of dietary protein levels by protein sparing from non-protein energy sources. Blood hematocrit content was not affected by dietary protein levels. However, a significantly lower amount of hemoglobin was found in fish fed 35 % CP than in fish fed 40, 45, 50, and 60 % CP diets. Fish fed 60 % CP showed the lowest survival rate than the fish fed 35, 40, 45, and 50 % CP diets. Broken-line analysis of WG showed the optimum dietary protein level was 45.2 % with 18.8 kJ/g diet for juvenile barred knifejaw. This study has potential implication for the successful cage culture of barred knifejaw.

Optimum Dietary Protein Level and Protein‐to‐energy Ratio for Growth of Juvenile Parrot Fish, Oplegnathus fasciatus

AbstractAn 8‐wk feeding trial was conducted to estimate the optimum dietary protein level and protein‐to‐energy (P/E) ratio in juvenile parrot fish, Oplegnathus fasciatus. Eight experimental diets were formulated with two energy levels and four protein levels for each energy level. Diets containing crude protein (CP) at 35, 40, 45, and 50% had either 12.5 or 14.6 kJ/g of energy. Fish averaging 7.1 ± 0.06 g (mean ± SD) were fed one of the experimental diets for 8 wk. At the end of the feeding trial, weight gain (WG) of fish fed 45 and 50% CP in the 12.5 kJ/g diet was significantly higher than fish fed the 35% CP diet (P &lt; 0.05). WG of the fish fed 45 and 50% CP in the 14.6 kJ/g diet was significantly higher than fish fed the 35 and 40% CP diets (P &lt; 0.05). Fish fed the 14.6 kJ/g diet had a higher WG compared with fish fed the 12.5 kJ/g diet at all CP levels. Feed efficiency (FE) and specific growth rate (SGR) showed a similar trend to the WG. WG, FE, and SGR improved with increasing dietary protein levels up to 45% and remained constant at 50% CP for both energy levels. However, protein efficiency ratio was negatively related to dietary protein levels. The results suggested that the optimum level of protein and the optimum P/E ratio for juvenile parrot fish should be 45% and 31.1 mg protein/kJ, respectively, in a diet containing 14.6 kJ/g energy.

Dietary protein requirement of juvenile obscure puffer,Takifugu obscurus

A 10-week feeding experiment was conducted to determine the optimum dietary protein requirement of juvenile obscure puffer (Takifugu obscurus). Six isoenergetic (20 MJ kg−1 gross energy) diets were formulated to contain graded levels of 34%, 38%, 42%, 46%, 50% or 54% crude protein (as dry matter basis). The results showed final body weight, weight gain and specific growth rate (SGR) increased significantly with increasing protein levels up to 42% and then decreased thereafer. Second-order polynomial regression analysis (y = −0.0024x2 + 0.1788x − 1.3196, R2 = 0.9032) indicated a maximum SGR at protein level of 37%. Feed conversion ratio (FCR) decreased with increasing levels of dietary protein up to 42% and increased thereafter. Second-order polynomial regression analysis (y = 0.0054x2 − 0.4351x + 10.391, R2 = 0.753) indicated a minimum FCR at protein level of 40%. Protein efficiency ratio (PER) of fish fed the 34%, 38% and 42% diets was significantly higher than that of fish fed the 46%, 50% and 54% diets, and broken-line analysis indicated PER tended to decrease when dietary protein level was higher than 40%. Generally, whole body lipid content, total cholesterol, low-density lipoprotein cholesterol and triacylglycerol decreased with increasing levels of dietary protein. Fish fed the 42% protein diet showed the highest essential amino acids (histidine, isoleucine, leucine, lysine and threonine) and non-essential amino acids (aspartic acid and glutamic acid) in muscle. Based on the second-degree polynomial regression analysis of SGR and FCR and broken-line analysis of PER, the optimal dietary protein level of obscure puffer is estimated to be between 37% and 40% (% as dry matter basis).

Development of a nutritional model to define the energy and protein requirements of cobia, Rachycentron canadum

This study assessed the protein and energy requirements of Cobia (Rachycentron canadum) using a bio-energetic factorial approach. Using a series of inter-related studies, several parameters were defined to enable the construction of a bio-energetic factorial model for this species. The studies included two controlled laboratory experiments and also extensive field-data collection from commercial and research farms in Vietnam. The devised model includes parameters for both maintenance and protein demands; the effect of fish live-weight on maintenance protein (LW0.697), lipid (LW0.972), and energy demands (LW0.815); the efficiencies of protein, lipid and energy utilisation at various protein, lipid and energy intake levels; and the variability in whole body composition with varying live-weight. The protein utilisation efficiencies (0.456·[protein intake]−0.445), lipid utilisation efficiencies (1.292·[lipid intake]−1.120) and energy utilisation efficiencies (0.651·[energy intake]−48.41) were similar to other carnivorous fish species. However, the maintenance requirements for both energy (74.3kJ/kgBW0.8/d− at 28°C) and protein (0.99g/kgBW0.7/d at 27.9°C) were about double to other species. Using this modelling approach it was possible to iteratively derive optimal dietary protein and energy specifications for this species.

Optimal dietary protein level improved growth, disease resistance, intestinal immune and physical barrier function of young grass carp (Ctenopharyngodon idella).

This study investigated the effects of dietary proteins on the growth, disease resistance, intestinal immune and physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp (264.11±0.76g) were fed six diets containing graded levels of protein (143.1, 176.7, 217.2, 257.5, 292.2 and 322.8g digestible protein kg(-1) diet) for 8 weeks. After the growth trial, fish were challenged with Aeromonas hydrophila and mortalities were recorded for 14 days. The results indicated that optimal dietary protein levels: increased the production of antibacterial components, up-regulated anti-inflammatory cytokines, inhibitor of κBα, target of rapamycin and ribosomal protein S6 kinases 1 mRNA levels, whereas down-regulated pro-inflammatory cytokines, nuclear factor kappa B (NF-κB) P65, NF-κB P52, c-Rel, IκB kinase β, IκB kinase γ and eIF4E-binding proteins 2 mRNA levels in three intestinal segments of young grass carp (P<0.05), suggesting that optimal dietary protein level could enhance fish intestinal immune barrier function; up-regulated the mRNA levels of tight junction complexes, B-cell lymphoma protein-2, inhibitor of apoptosis proteins, myeloid cell leukemia-1 and NF-E2-related factor 2, and increased the activities and mRNA levels of antioxidant enzymes, whereas down-regulated myosin light chain kinase, cysteinyl aspartic acid-protease 2, 3, 7, 8, 9, fatty acid synthetase ligand, apoptotic protease activating factor-1, Bcl-2 associated X protein, p38 mitogen-activated protein kinase, c-Jun N-terminal protein kinase and Kelch-like-ECH-associated protein 1b mRNA levels, and decreased reactive oxygen species, malondialdehyde and protein carbonyl contents in three intestinal segments of young grass carp (P<0.05), indicating that optimal dietary protein level could improve fish intestinal physical barrier function. Finally, the optimal dietary protein levels for the growth performance (PWG) and against enteritis morbidity of young grass carp were estimated to be 286.82gkg(-1) diet (250.66g digestible protein kg(-1) diet) and 292.10gkg(-1) diet (255.47g digestible protein kg(-1) diet), respectively.

Effects of protein levels on growth, feed utilization, body composition, amino acid composition and physiology indices of juvenile chu's croaker,Nibea coibor

A 49-day feeding trial was conducted to determine the optimal dietary protein level for juvenile chu's croaker Nibea coibor in sea cages. Five isocaloric diets were formulated to contain graded levels of protein: 360 (D36), 400 (D40), 440 (D44), 480 (D48) and 520 (D52) g kg−1 diet. Each diet was randomly assigned to triplicate groups of 25 fish (mean 76.0 ± 0.8 g) in a total of 15 floating cages. Specific growth rate (SGR), protein retention efficiency (PRE), feed efficiency and feed intake were significantly higher at D44 and D48. Consumed protein (CP) obtained the maximum at D48, and protein efficiency ratio was significantly higher in fish fed with D44 and D48 compared with fish fed with D36 and D52. Hepatosomatic index and condition factor were not affected. Body protein and moisture content increased with increasing dietary protein, while lipid and ash content were not affected. Individual and total essential amino acids maximized at D44. Digestive enzymes and physiology indices in intestine, liver and plasma were differentially affected. Based on polynomial regression analysis of SGR, PRE and CP, we suggested that the optimum dietary protein level for juvenile chu's croaker was 444–478 g kg−1 diet.

Effects of Dietary Protein Level on Nitrogen and Energy Budget of Juvenile Chinese Soft‐shelled Turtle, Pelodiscus sinensis, Wiegmann

AbstractThe effects of dietary protein level on nutrient digestibility and utilization of protein and energy of juvenile Chinese soft‐shelled turtle, Pelodiscus sinensis, were investigated. Seven isoenergetic diets containing graded levels of protein (25, 27, 29, 31, 33, 35, and 43%) were fed to turtles initially averaging 4.8 ± 0.7 g for 8 wk at 30 ± 0.5 C. The apparent digestibilities of dry matter, protein, and energy were generally increased with dietary protein level. Proportions of nitrogen intake (CN) allocated to excretory nitrogen (UN) were higher in 25 and 43% protein diets than the other diets. UN proportion was lowest in the 33% protein diet, whereas retained (growth) nitrogen (RN) followed an inverse pattern with UN. Percentages of gross energy intake (IE) used for excretory energy (UE) generally increased when dietary protein levels increased. Turtles fed 25–29% protein diets showed a markedly higher proportion of metabolizable energy (ME) than those fed 31–43% protein diets. Analysis by second‐order polynomial regression using RN as the indicator indicated that the estimated optimal dietary protein level was 34.6%. The lowest and highest percentages of retained (growth) energy (RE) were observed in the 25 and 33% protein groups. Nitrogen and energy budget equations of turtles fed 33% protein diet were 100 CN = 8.22 FN + 37.48 UN + 54.30 RN and 100 IE = 10.88 FE + 2.82 UE + 65.60 ME + 20.69 RE, respectively. Diets with excessive protein resulted in high proportions of protein and energy used for excretion.

Dietary protein requirement of juvenile bluegill sunfish (Lepomis macrochirus)

Five semi-purified diets were formulated with varying crude protein (CP) level (ranging from 20.77 to 45.69%) to assess the dietary protein requirement of juvenile bluegill sunfish (Lepomis macrochirus). Each diet was given to triplicate groups (20 fish per group, 1.20g per fish) for 10weeks. In this study, the weight gain (WG) values showed a general increasing trend with increasing dietary CP level up to 40.23%, and then no further improvement of growth was observed with further increase in dietary CP level. In addition, feed efficiency (FE) also improved with increase in dietary CP level; the maximum value was observed in fish fed diet with 40.23% CP. Besides, fish fed diets with 20.77 and 28.16% CP had significant higher daily feed intake (DFI) and lower energy retention (ER), lipid retention (LR) and nitrogen retention (NR) values than other treatments (P<0.05). Moreover, fish fed 20.77% CP diet with the highest starch content showed the highest hepatosomatic index (HSI) and relatively higher liver glycogen content than other groups. However, no significant difference in liver lipid content was observed among all dietary treatments. Fish fed diets with 20.77 and 28.16% CP had a relatively lower whole body protein and dorsal muscle protein content than other treatments. Based on broken-line regression analysis, the optimal dietary protein content for sunfish is about 41.51 to 42.37%. Statement of RelevanceThe main aim of this study is to quantify the optimum amount of dietary protein for juvenile bluegill sunfish (L. macrochirus).The research outcomes will develop formulated diets for L. macrochirus and will have good potential of being commercialized.

Optimizing energy, protein and amino acid needs in diet of starting and growing Aseel chicks

A study was conducted involving day-old Kadaknath chicks (n=288) to evaluate their optimum dietary energy, protein and amino acid levels for 0–20 weeks of age. Six dietary treatments with two levels of energy (2700 kcal and 2500 kcal ME/kg) each with three levels of protein (20, 18 and 16%), following 2 x3 factorial design, were formulated. Each of such diet was randomly allotted to 4 replicated groups of 12 chicks each kept in battery brooder cages for 0–12 weeks of age. In second experiment female Kadaknath growing chicks 12 wks of age (n=120) were randomly re-distributed to six dietary treatments with two levels of energy (2700 kcal and 2500 kcal ME/kg) each with three levels of protein (16, 14 and 12%) following a 2 x 3 factorial design were formulated and each of such diet was randomly offered to 4 replicated groups of 5 growing chicks each kept in growing cages from 12 to 20 wks of age. Results indicated that body weight gain of chicks (0-12wk) fed 2700 kcal ME/kg diet was significantly higher (P<0.01) than those fed diets with 2500 kcal ME/kg. Feed conversion ratio was better in 2700 kcal ME/kg in comparison to those fed 2500 kcal ME/kg. Body weight gain of chicks (0–12 wks) fed 18 and 20% CP was significantly higher in comparison to chicks those fed 16% CP. The gain in body weight during 12–20 weeks of age remained similar in all the protein levels and protein x energy interaction but significantly higher gain in body weight was recorded at low energy than higher energy diet. Feed intake was recorded significantly higher (P<0.001) at low energy than high energy diet but feed conversion efficiency remained similar due to different energy levels. The feed conversion efficiency and ME efficiency were significantly lower in low protein diet whereas protein efficiency was comparable in different protein levels in diet. The results revealed that the optimum dietary energy, protein and amino acid levels for 0–12 wks age Kadaknath chicks were 2700 kcal ME/kg, 18% CP and 1.12% lysine, 0.50% methionine and 0.70% threonine, respectively. Whereas during 12–20 weeks of age, dietary energy level of 2500 kcal ME/kg with 14% CP, 0.66% lysine, 0.30% methionine and 0.54% threonine was optimum.