Specific Growth Ratio Research Articles

Physical processing or supplementation of feeds with phytogenic compounds, alginate oligosaccharide or nucleotides as methods to improve the utilization of Gracilaria gracilis by juvenile European seabass (Dicentrarchus labrax)

This study assessed both the effectiveness of a physical-mechanical rupture method and the ability of feed additives (phytogenic compounds, alginate oligosaccharide and nucleotides) to enhance the utilization of G. gracilis by European seabass. A commercial-based diet was used as control diet (CTRL) and compared with five isoproteic (53.5% Dry matter, DM) and isolipidic (14.9% DM) diets containing 8% of G. gracilis. This seaweed was either unprocessed (diet GRA) or subjected to physical processing (diet GRAP). The three additive-containing diets were formulated by supplementing the GRA diet with either 0.02% phytogenic compounds (PHY), 2.5% oligo-alginate (OAS) or 0.08% free nucleotides (NUC). Triplicate groups of nineteen fish (29.7 ± 0.02 g) were distributed by 50 L tanks (11.3 kg m−3) and fed the experimental diets to satiety during 106 days. By the end of the trial, growth performance and nutrient utilization (specific growth ratio, feed conversion ratio, apparent digestibility coefficients, nutrient balance, intestinal brush border membrane enzyme activities and plasma metabolic parameters), gut histomorphology, antioxidant and immunological status of fish were evaluated. The ability of fish to digest seaweed-rich diets was largely improved by the technological processing of G. gracilis, albeit nil effect on fish specific growth rate (1.0 in all groups). This major achievement was associated with increased ability of GRAP to digest protein (84 vs 68% in GRA) and energy (64 vs 38% in GRA). The use of feed additives in Gracilaria-rich diets was less efficacious in improving European sea bass nutrient and energy ADCs, but have still improved the overall digestibility of those diets. Fish fed alginate oligosaccharide was mainly associated with increased activity of anterior intestine enzymes, particularly intestinal alkaline phosphatase (IAP; 174.4 vs 104.7–120.6 μm min−1 g−1 in Gracilaria-rich diets). Moreover, the algae technological processing and both the nucleotides and the alginate oligosaccharide seem to have positively affected the intestinal villus width compared to the negative impact seen in fish fed GRA. The tested additives had limited impact on oxidative stress, although glutathione peroxidase (GPx; 2.1 μmol min−1 mg protein−1) and catalase (CAT; 35 μmol min−1 mg protein−1) activities were lowest in fish fed NUC and PHY, respectively. It can be concluded that the physical processing of Gracilaria sp. or the addition of either oligo-alginate or nucleotides can effectively increase the nutritional value of this seaweed for European seabass diets.

Cyclical fasting and refeeding is not an advisable feeding strategy for white shrimp (Penaeus vannamei)

This study investigated the effects of cyclical fasting and refeeding on growth performance, digestibility, muscle composition and mTOR signaling pathway of Penaeus vannamei. Three feeding strategies were designed: feeding everyday of a week (control); fasting one day and refeeding six days of a week (F1), fasting two days and refeeding five days of a week (F2). Shrimp with initial body weight of 6.52 ± 0.46 g was used for feeding strategy experiments. The stocking density was 20 shrimps (130.4 g biomass) per 100 L seawater. There were no significant differences in growth performance (final weight, weight gain and specific growth ratio), muscle composition (moisture, crude protein, crude lipid and ash contents) and digestive enzyme activity (trypsin, α-amylase and lipase) among three treatments (P > 0.05). However, survival rate of control treatment was significantly higher than that of F1 and F2 treatments (P < 0.05). Feed efficiency (FE) of shrimp in F1 and F2 treatments were higher than that of shrimp in control treatments. The expression level of trypsin in F1 and F2 treatments were significantly up-regulated than that of control treatment (P < 0.05). Both tor and s6k expression levels of F1 and F2 treatments were up-regulated than those of control treatment. These results suggest that the compensatory growth response of shrimp caused by starvation and refeeding may be attributed to the high feed efficiency after starvation and refeeding or the cannibalism caused by starvation, which provides a better source of protein for shrimp and promotes the growth performance of shrimp. However, considering the low survival rate, cyclical fasting and refeeding is not an advisable feeding strategy for P. vannamei.

Dietary Different Replacement Levels of Fishmeal by Fish Silage Could Influence Growth of Litopenaeus vannamei by Regulating mTOR at Transcriptional Level.

Fish silage (FS) has been confirmed as a high-quality feed ingredient because of its balanced nutrition, low cost, and environmental friendliness. In the present study, we evaluated the performance of replacing fishmeal by FS in the diet of white shrimp, Litopenaeus vannamei. Five isonitrogenous (410 g kg–1) and isolipidic (75 g kg–1) diets were formulated with replacement of fishmeal by 0% (FM), 25% (FS25%), 50% (FS50%), 75% (FS75%), and 100% (FS100%) FS. After an 8-week trial, shrimps fed low FS diets (FM and FS25%) had significantly higher final weight (FW), weight gain (WG), and specific growth ratio (SGR) (P < 0.05). No significant differences were found in body composition and most antioxidant enzyme activities of all groups (P > 0.05). Compared to high FS groups (FS75% and FS100%), low FS replacement levels (0 and 25%) had enhanced trypsin activity. And trypsin transcriptional level presented a similar trend with trypsin activity. In terms of intestinal histopathology, no obvious histological damage was observed in the intestine of all groups. tor and s6k of low replacement level groups (FM and FS25%) were significantly upregulated (P < 0.05), which indicated activation of mammalian target of rapamycin (mTOR) signaling pathway in low FS groups at transcriptional level. The enhanced performances of growth and mTOR signaling pathway in low FS groups (FM and FS25%) provided us some insights into the regulation mechanism of nutrient signal on growth. Based on the above, dietary FS could influence the growth of shrimp by regulating mTOR at the transcriptional level, and FS is a potential substitute of fishmeal in shrimp feed.

Effects of corn starch level on growth performance, antioxidant capacity, gut morphology and intestinal microflora of juvenile golden pompano, Trachinotus ovatus

Carbohydrates are the cheapest source of dietary energy for fish. Utilization of carbohydrates in feed is beneficial to sparing protein consumption as energy source and saving feed cost. Therefore, 8-week feeding experiment was conducted to investigate the effects of starch level on growth performance, antioxidant capacity, serum biochemical parameters, intestinal morphology and intestinal microbiota of Trachinotus ovatus. Six isonitrogenous and isolipidic diets (D1, D2, D3, D4, D5 and D6) containing 0%, 5%, 10%, 15%, 20% and 25% corn starch were formulated, respectively. Each diet was randomly assigned to triplicate groups of fish (initial body weight 11.84 g) fed twice daily to apparent satiation. Results showed that percent weight gain, specific growth ratio, hepatosomatic index, total antioxidation capacity and glutathione content of fish fed with D6 diet were the highest among all experimental treatments. Feed conversion rate was significantly lower in fish fed with D5 and D6 diets, than in fish fed with D1-D4 diets. No significant differences were found in the survival rate, viscerasomatic index, malondialdehyde and serum triglyceride contents among all diet treatments. The superoxide dismutase activity of T. ovatus fed with D3-D6 diets were relatively higher than those fed with D1 and D2 diets. Fish fed with D3 diet showed the highest value of serum total cholesterol. High-density lipoprotein cholesterol / low-density lipoprotein cholesterol ratio of fish fed with D1 and D6 diets were relatively higher than those fed with D2-D5 diets. No significant pathological changes in the foregut were observed among all diet treatments. Dietary starch level lead to alterations in the intestinal microbiota in T. ovatus. D2-D5 dietary treatments increased the abundance of harmful bacteria such as Vibrio, Photobacterium, Mycoplasma. D1 and D6 dietary treatments had similar intestinal microbiota composition. In conclusion, 25% starch level was beneficial to the growth and health of T. ovatus.

Effect of the digestible protein-energy relationship on the growth performance of Nile tilapia (Oreochromis niloticus) fed fishmeal-free diets

This study aimed to determine the best digestible protein: digestible energy (DP:DE) ratio for adult Nile tilapia (Oreochromis niloticus) fed diets formulated with vegetable ingredients (soybean and corn), and without fishmeal. Four hundred and twenty male Nile tilapia (GIFT strain) (initial mean weight 193 ± 12.6 g) were allocated to 60 plastic tanks (1000 L) connected to a water recirculation system, and there were 7 fish in each tank. The experimental design was a 5 × 4 factorial with three replicates for each diet treatment. The fish were fed one of 20 diets containing a combination of five digestible protein levels (140, 190, 240, 290 and 340 g/kg DP) and four digestible energy levels (10.89, 11.72, 12.56 and 13.40 MJ/kg DE) for 96 days. The fish were given three meals each day (8 AM, 1 PM and 6 PM) and feeding was to apparent satiation. At the end of the experimental period, diets presented an interactive effect (P < 0.05) in relation to the productive performance. Final weight (FW = 448.82 g), fillet yield (FY = 32.60 %) and specific growth ratio (SGR = 2.65 %) were increased and a decrease in feed conversion ratio (FCR = 1.20) was observed in diet containing 240 g/kg DP and 12.56 MJ/kg DE. Otherwise, the highest protein efficiency ratio (P < 0.05) was found in diet containing 140 g/kg DP and 12.56 MJ/kg DE. FW, WG, FY and SGR were increased significantly (P < 0.05) up to the 12.56 MJ/kg DE level, independent of digestible protein levels. A quadratic effect was observed for FW, WG and SGR, independent of energy levels. An increase in these variables was observed up to 250.78, 240.70 and 216.70 g/kg DP respectively, and the lowest FCR was 260.58 g/kg DP. A linear increase was observed for FY (P < 0.05) in diets containing higher DP levels. No interaction (P > 0.05) was observed in any treatment for fillet centesimal composition and whole body. However, an increase (P < 0.05) in crude protein of fillet and body moisture was observed in diets containing levels above 240 g/kg DP, independent of DE. The present findings indicate that the optimal DP:DE level was 240 g/kg DP and 12.56 MJ/kg DE in the fishmeal-free diets for males Nile tilapia, promoting adequate growth performance without affecting the proximal tissue composition.

Effects of the replacement of fishmeal by soy protein concentrate on growth performance, apparent digestibility, and retention of protein and amino acid in juvenile pearl gentian grouper.

Soy protein concentrate (SPC), as a protein source, is widely used to replace partial fishmeal (FM) in aquafeeds, especially for carnivorous fish. This study investigated the effects of partial FM replacement by SPC for juvenile pearl gentian grouper. The fish were fed with diets containing six levels of SPC (SPC 0, 15, 30, 45, 60, and 75) for 6 weeks. At the end of the feeding trial, average body weight gain (BWG), specific growth ratio (SGR), and weight gain ratio (WGR) had the highest values in fish fed with diet SPC 15, followed by that of fish fed with SPC 0 while fish fed with SPC 75 had the lowest values (P < 0.05). Fish fed with diet SPC 15 and SPC 30 had the highest protein efficiency ratio (PER) while fish fed with diet SPC 15, SPC 30, and SPC 45 had the highest feed conversion ratio (FCR) (P < 0.05). Daily feed intake (DFI) was significantly decreased in fish fed with diets containing any level of SPC (P < 0.05). Survival rate was significantly higher in fish fed with diets SPC 15, SPC 30, and SPC 45 as compared to other treatments. Fish fed the diet including less than 30% FM replacement showed a higher protein content in the muscle. The ADC of dietary protein and some amino acids were significantly higher in diets SPC 0, followed by SPC 15; while SPC 75 had the lowest content (P < 0.05). Similarly, fish fed with SPC 30 and SPC 15 showed significantly higher protein and amino acid (AA) retention than other dietary treatments. The optimal FM replacement with SPC for specific growth ratio (SGR) was estimated to be 14.41% using a non-linear higher order regression model. These results indicated that pearl gentian grouper has a limited ability to utilize SPC as a protein source, and the FM replacement with SPC should be less than 30% (FM45.5 g 100g -1 and SPC18g 100g -1).

Effect of dietary iron levels on growth, iron concentration in tissues, and blood concentration levels of transferrin and hepcidin in bighead carp (Aristichthys nobilis)

A 60‐day feeding trial was conducted to estimate the effects of dietary iron (Fe) levels on growth, Fe concentration in the liver, spleen, and blood, and transferrin and hepcidin concentrations in the blood of bighead carp (Aristichthys nobilis). The six experimental diets were formulated to contain different Fe levels (0, 43.1, 84.2, 123.3, 162.2 and 203.1 mg/kg of dry diet) using ferrous sulphate (FeSO₄) as the source. The weight gain (WG) and the specific growth ratio (SGR) of A. nobilis fed with a dietary Fe level of 123.3 mg/kg were significantly higher than that of the 0 mg/kg Fe group (p liver > whole body. When the Fe dietary content increases to 162.2 mg/kg, the blood concentrations of Fe significantly decreased and thereafter increased, hepcidin significantly decreased and thereafter decreased, and transferrin significantly increased and thereafter decreased. The results indicate that the transferrin blood content significantly increased with decreasing hepcidin of up to 264.63 μg/ml content and thereafter decreased. It could be concluded that after transferrin saturation, hepcidin functions to maintain iron balance in the blood of A. nobilis by decreasing transferrin content.

Emodin ameliorates metabolic and antioxidant capacity inhibited by dietary oxidized fish oil through PPARs and Nrf2-Keap1 signaling in Wuchang bream (Megalobrama amblycephala)

Dietary lipids and fatty acids are involved in cell metabolism and animal physiological regulation. However, oxidized lipids could induce oxidative stress and disorder normal growth and physiological health in fish. A 12-week rearing experiment with 6% fish oil (6F), 6% oxidized fish oil (6OF) and emodin supplemented diets (6F + E, 6OF + E) was conducted to evaluate the protective mechanism of emodin on oxidized fish oil stress in Megalobrama amblycephala. Results indicate that, under oxidized fish oil stress, emodin rescued the growth performance inhibition, improved special growth ratio (SGR), and reduced feed conversion ratio (FCR) and hepatosomatic index (HSI); rescued intestine histological impairment, ameliorated the structural expansion and membrane damage of mitochondria in intestine cells, and increased the length and intensity of intestinal villus. Moreover, emodin enhanced serum immune and antioxidant enzyme activity, increased metabolic activity through PPARs signaling, increased antioxidant capacity through PPARs and Nrf2-Keap1 signaling based on the transcriptional expression of specific genes. These results indicate emodin could be used as an effective immunostimulant to protect organism form oxidative stress induced by dietary oxidized lipid. This may provide insights for oxidized lipid prevention in aquaculture production.

Farklı Oranlarda Fındık, Soya Küspesi, Balık Unu ile Birlikte Fitaz İçeren Rasyonların Gökkuşağı Alabalığı (Oncorhynchus mykiss) Yavrularının Gelişimi Üzerine Etkileri

This study aimed to examine the effects of six trial diets (containing different amounts of fish meal, hazelnut, and soybean meal protein, also without the enzyme phytase “0 FTU” and with “1000 FTU”) on the rainbow trout (Oncorhynchus mykiss) juveniles. The study was conducted as three replicates. Live weight gain, feed consumption, feed conversion ratio, specific growth ratio and the protein efficiency ratio of the trial groups were calculated as 52.8-64.3g, 64.1-72.1g/fish, 1.12-1.22, 1.42-1.6% and 1.79-2.0, respectively (P&amp;lt;0.05). The dietary factors did not produce a significant effect on the organ indexes, body chemical composition, digestibility ratios of diets in the fish (P&amp;gt;0.05). But phytase enzyme affected significantly the dietary phosphorus ratio and the digestible energy ratio (P&amp;lt;0.05). Dry matter, crude ash, crude lipid, crude protein and phosphorus components in the fish bodies were found to be 30.7-31.8%, 2.2-2.3%, 11.8-12.8%, 14.5-15.2% and 0.56-0.62%, respectively. In the trial group fishes, values of the total nitrogen and phosphorus consumption, gain and retention were calculated as 1139-1173 mg/kg versus 248-279 mg/kg, 315-350 mg/kg versus 73-82 mg/kg, and 27.2-30.6% versus 26-33%, based on the average daily weight. Generally, the interaction between factors was found to be statistically insignificant (P&amp;gt;0.05).

Effects of chitooligosaccharides supplementation with different dosages, molecular weights and degrees of deacetylation on growth performance, innate immunity and hepatopancreas morphology in Pacific white shrimp (Litopenaeus vannamei)

Three trials were conducted to comprehensively evaluate the application of chitooligosaccharides (COSs) different dosages, molecular weights (MW) and degrees of deacetylation (DD) as a feed additive for Pacific white shrimp (Litopenaeus vannamei). In trial 1, COSs (3 KDa and 85% DD) at four different dosages (0.05%, 0.1%, 0.15% and 0.2%) were added to feed to investigate the appropriate dosages. The survival ratio (SR) of the shrimps was not significantly different (P > 0.05) between the control and treatment groups. The shrimps fed with 0.1% COSs supplementation exhibited the highest wet body weight (FBW), specific growth ratio (SGR), and weight gain (WG) and the lowest feed conversion ratio (FCR). In trial 2, COSs with different MW (85% DD and 0.1% dosage) were tested. Except for the group treated with the 12 KDa COSs, all shrimps fed with COSs had remarkably higher (P < 0.05) FBW, WG, and SGR and lower FCR (P < 0.05) than the control group, and shrimps fed with the 1 KDa COSs showed most positive effects. In trial 3, COSs with different DD (MW of 1 KDa and 0.1% dosage) were further studied. The different DD were DD5, DD25, DD50, DD75, and DD95. Shrimps fed COSs-supplemented diets of DD75 or DD95 exhibited higher (P < 0.05) FBW, WG and SGR and lower FCR than the other groups. The DD95 group had the highest FBW, WG and SGR and the lowest FCR, but there were no significant differences (P > 0.05) between the DD75 and DD95 groups. Moreover, for COSs supplementation, especially for the DD75 and DD95 groups, the antioxidant parameters were significantly different from those of the other groups. Furthermore, groups fed diets with COSs supplementation had higher (P < 0.05) trypsin activity than those fed control diets. In addition, immune and antioxidant gene expression and the morphology of the hepatopancreas were affected by the DD of COSs. Therefore, the additive dosages, molecular weights and degrees of deacetylation of COSs significantly affected the growth performance of the shrimps; therefore, it is particularly important to determine the optimum parameters of COSs.

Characteristics of Growth and Fluorescence of Certain Types of Algae during Acclimation to Different Temperatures under Culture Conditions

The paper examines the temperature dependence of the specific growth rate and ratio of variable to maximum fluorescence (FV/FM) in a number of marine planktonic algae from collections of cultures. It determines the optimum growth temperatures (Topt), upper and lower limits of the tolerance zone, and in some cases, changes in the dynamics of these parameters outside the tolerance zone. Temperature characteristics of the species corresponded to the growth conditions of these species in a natural environment. Prolonged stress exposure to a low positive temperature (4–6°C) was reversible; recovery of the growth rate and FV/FM was observed immediately after the temperature increased. In diatoms, temperatures 2–3°C above the Topt for diatoms induced gradual degradation of the culture, which, depending on the duration of exposure, could lead to the death of algae. Springtime dinoflagellates exhibited higher temperature resistance and remained viable at temperatures 5–8°C above Topt with lower specific growth rates. The increasing portion of temperature dependence of the specific growth rate approximated a linear dependence; the regression coefficient is 0.08–0.13 for diatoms and 0.03–0.11 for dinoflagellates. The normalized values for this parameter (the relative value of change in the specific growth rate, %) was 5.3 ± 0.4 for diatoms and 6.4 ± 0.5 for dinoflagellates for 1°C of temperature change. Dinoflagellates exhibited larger values for the Q10 parameter. FV/FM for most species had high values in the entire range of temperatures at which the algae maintained a steady-state growth. A drop in this parameter outside the limits of the tolerance zone was associated with the temperature-induced inhibition of growth processes.

Growth Performance, Digestive Enzymes, and TOR Signaling Pathway of Litopenaeus vannamei Are Not Significantly Affected by Dietary Protein Hydrolysates in Practical Conditions.

Protein hydrolysates have been widely reported as the protein source of aquatic feed. However, previous studies on protein hydrolysates focused on fish under experimental conditions. In this study, a 6-week feeding trial in a greenhouse was conducted to investigate the effects of partially replacing fishmeal by protein hydrolysates on growth performance, digestive enzymes, and TOR signaling pathway of Litopenaeus vannamei under practical conditions. This involved randomly selecting 72,000 shrimps (initial body weight 2.26 ± 0.02 g) and placing them in groups inside nine concrete tanks (L 5 m × W 5 m × H 1 m) (3 treatments × 3 replicates × 8000 individuals per concrete tank). Two isonitrogenous (430 g kg-1) and isolipidic (80 g kg-1) diets were prepared: fishmeal diet (FM) containing 400g kg-1 fishmeal, and protein hydrolysates diet (PH) in which 15% of the fishmeal was replaced by protein hydrolysates. A commercial diet (CD) was used as reference. The final weight (FW), percent weight gain (PWG), specific growth ratio (SGR), and total weight for each tank (TW) of L. vannamei fed with FM and PH diets were not significantly different (P > 0.05). However, shrimp fed with PH diet had significantly higher FW, PWG, SGR, and TW values than those fed with CD diet (P < 0.05). Trypsin activity was significantly lower in shrimp fed with CD diet, than in shrimp fed with FM and PH diets (P < 0.05). However, trypsin activity of L. vannamei fed with FM and PH diets were not significantly different (P > 0.05). The mRNA expression of tor, s6k, and 4e-bp genes were not significantly affected between FM and PH diets, while tor and s6k expression levels of CD diet were significantly down-regulated. Based on the above data, 15% replacement of fishmeal with protein hydrolysates did not make any difference on shrimps compared with FM group. Therefore, protein hydrolysates can partially replace fishmeal as the protein source of shrimp formula feed in practical conditions.

Oil sources administered to tambaqui (Colossoma macropomum): growth, body composition and effect of masking organoleptic properties and fasting on diet preference

Tropical fish feeding behaviour and food intake are regulated by a number of environmental factors (e.g.: stress in intensive aquaculture; type or seasonality of food), and also by complex homeostatic mechanisms that involve nutritional requirements. When access to food is not restricted, e.g. controlled laboratory conditions, fish growth and behaviour remain relatively unaffected. Moreover, fish need dietary fatty acids and, while some are remarkably beneficial, such as long-chain omega-3 oils, other fats can be associated with poor health, mainly under adverse conditions. This study aimed to evaluate the performance and body composition of tambaqui juveniles fed different oil sources (fish, linseed, and corn) (Experiment 1) and the influence of post-absorptive signals or orosensorial properties of the dietary oil source on diet preference (Experiment 2). For Experiment 1, juvenile tambaqui (42.79±0.92g) were placed into eighteen 100L tanks (10 fish per tank). Three diets (treatments) were formulated with three oil sources (corn, linseed and fish oil). Three groups of fish were fed each separate diets twice a day for 7 weeks. Experiment 2 assessed tambaqui’s ability to select oil sources without coming into contact with the sensorial properties of diet. The same diets of Experiment 1 were used, but diets were encapsulated to isolate sensorial properties. Forty-eight fish (41.26±1.00g, mean±SD) were distributed into six 250L tanks (eight fish per tank). In experiment 1, we found no effects of diet on growth parameters, such as final body weight, weight gain, feed intake, feed efficiency ratio, specific growth ratio and protein efficiency (p≥0.05). However, body crude protein was higher in the fish fed the corn oil diet (p≤0.05), but this value did not affect the protein efficiency ratio (p≥0.05). No differences among treatments were observed for moisture, lipid and ash (p≥0.05). The fatty acid composition of muscle reflected the dietary oil source. However, the tambaqui fed vegetable oil displayed high levels of polyunsaturated fatty acids, while the linseed oil diet resulted in a greater incorporation of n-3 highly unsaturated fatty acids. In Experiment 2, at first fish did not show the ability to select an oil source without orosensorial properties, but a nutritional challenge of food deprivation (10days) enabled fish to select among the diets that contained fish oil sources (p=0.002) by using post-ingestive signals. Our findings contribute to the understanding of the mechanisms that relate to lipid metabolism and feeding behaviour in freshwater Amazon species, which goes beyond growth parameters.

Evaluation of the red alga Gracilaria lemaneiformis and brown alga Sargassum horneri as ingredients in diets for white spotted snapper Lutjanus stellatus Akazaki juveniles

This study evaluated the red alga Gracilaria lemaneiformis and brown alga Sargassum horneri as ingredients to partially replace fishmeal in diets for white spotted snapper Lutjanus stellatus Akazaki (initial mass 12.0 ± 0.1 g). Nine test diets containing 0 (control), 5, 10, 15, and 20% G. lemaneiformis or S. horneri were prepared; each diet was assigned to triplicate groups of fish in a total of 27 floating sea cages (each cage contained 30 fish). After a 60-day feeding trail, significantly lower final body weight, weight gain, and specific growth ratio were found in fish fed 20% G. lemaneiformis diet (P < 0.05), whereas the poorest fish growth performance was obtained with the 20% S. horneri diet. Lipid content in muscle of fish fed 20% G. lemaneiformis diet was significantly lower than that of other groups (P < 0.05); however, body protein was higher than that in other groups. The lowest lipid and moisture contents in muscle were recorded in fish fed 5 and 15% S. horneri diets, and protein content in whole body of fish fed 20% S. horneri diet was significantly lower than that of control and 5% diets (P < 0.05). Activities of pepsin in the stomach and lipase and amylase in the intestine were significantly suppressed in fish fed 20% G. lemaneiformis diet compared with that of control (P < 0.05). The lowest pepsin activity in stomach and lipase activity in intestine were observed in fish fed 20% S. horneri diet. Based on a quadratic regression model of weight gain, the results suggested that the maximum incorporation of G. lemaneiformis and S. horneri in diets should be 16.44 and 15%, respectively, for juvenile white spotted snapper.

Effect of dietary leucine on growth performance, hemolymph and hepatopancreas enzyme activities of swimming crab,Portunus trituberculatus

An 8-week feeding trial was conducted to determine the dietary leucine requirement for juvenile swimming crabs reared in cement pools. Six isonitrogenous and isolipidic practical diets (430 g/kg crude protein and 70 g/kg crude lipid) were formulated to contain graded leucine levels which ranged from 16.7 to 26.7 g/kg (dry weight). Each diet was randomly assigned to triplicate groups of 60 juvenile swimming crabs (initial average weight 3.75 ± 0.12 g) that were stocked in rectangle plastic baskets. The results of the present study indicated that dietary leucine levels significantly influenced weight gain (WG) and specific growth ratio (SGR) (p < .05), crab fed the diet containing 22.7 g/kg leucine had significantly higher WG and SGR than those fed the other diets. Feed efficiency and protein efficiency ratio were not significantly affected by the dietary leucine levels (p > .05). Total protein, cholesterol, triglyceride and glucose in serum were significantly affected by the dietary leucine levels. Aspartate aminotransferase (AST) and alanine aminotransferase activities in hemolymph, AST and superoxide dismutase activities in hepatopancreas were significantly affected by dietary leucine levels; moreover, crab fed the 16.7 g/kg leucine diet had higher malondialdehyde in hemolymph and hepatopancreas than those fed the other diets. Crab fed the diet containing 24.9 g/kg leucine had higher phenoloxidase activity in hemolymph than those fed the other diets. Based on two-slope broken-line model of SGR against dietary leucine levels, the optimal dietary leucine requirement for growth was estimated to be 22.1 g/kg of the dry diet (corresponding to 51.4 g/kg of dietary protein on a dry weight basis). In summary, findings of this study indicated that dietary leucine could improve growth performance and antioxidant status.

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeriBrandt♀×A. schrenckiiBrandt♂

The growth performance, body composition, fillet fatty acid content, serum hepatic enzymes and postprandial changes in serum lipid metabolism of hybrid sturgeon (70.8 ± 0.5 g) were investigated to determine the effects of total replacement of 80 g kg-1 fish oil (diet A) with linseed oil (diet B) and soybean oil (diet C), respectively. No significant differences in weight gain rate and specific growth ratio were observed among all fish groups (p > .05). Diet A fish group had the highest, but diet B fish group had the lowest feed intake (p .05). In summary, total replacement of fish oil with linseed oil or soybean oil had no significant adverse effects on hybrid sturgeon growth during 84-day period, and linoleic acid and linolenic acid in fillet were modified by dietary treatments.

Effect of salinity on the growth performance, osmolarity and metabolism-related gene expression in white shrimp Litopenaeus vannamei

An 8-week feeding trial was conducted to study the effect of long-term low-salinity stress on the growth performance, and expression of osmolarity and metabolism-related genes (Na+-K+-ATPase α-subunit and in gills, trypsin and chymotypsin in hepatopancreas) in white shrimp (L. vannamei). Four groups of the white shrimp (mean initial weight, 0.31±0.02g) were cultivated at salinity of 2, 10, 20 and 30psu for 8-week. All treatments were conducted in triplicate of 40 each. The results indicated that shrimps reared at salinity 20psu and 30psu were significantly higher in final weight, weight gain and specific growth ratio than the other treatments (p<0.05 when compared to 2 and 10), and those reared at salinity 2psu were significantly lower than the other treatments in growth performance and survival (p<0.05 when compared to other treatments). Quantitative real-time PCR (qRT-PCR) results indicated that Na+-K+-ATPase α-subunit and carbonic anhydrase mRNA levels at salinity 2psu and 10psu were increased significantly 1.79-, 1.65-fold and 3.22-, 2.31-fold respectively according to salinity 20psu, chymotrypsin and trypsin mRNA level at salinity 10psu and 2psu decreased significantly 15%, 36% and 72%, 45% respectively according to salinity 30psu. In conclusion, low salinity could, to some extent, reduce growth performance and survival significantly, and influence transcript levels of Na+-K+-ATPase α-subunit, carbonic anhydrase in gills and chymotrypsin, trypsin in hepatopancreas.

Survival and growth of early life stages of leaf fish (Monocirrhus polyacanthus , Heckel 1840) cultured under different stocking densities and live food densities

The objective of this study was to evaluate the effects of different live foods, (Artemia sp. and Moina minuta), and different stocking densities on the larval rearing success of the leaf fish, Monocirrhus polyacanthus. A completely randomized factorial design (3 × 3; three replicates) was used. Two subsequent experiments were performed for each live food, using three food densities (100, 200 and 300 prey per larva) and three stocking densities (10, 15 and 20 larvae L−1). Fish were fed twice a day. Water quality parameters pH (4.08–4.02), dissolved oxygen (3.7–3.6 mg L−1), temperature (27.9–27.8°C), conductivity (147.2–127.4 μs cm−1) and total ammonia (0.78–0.38 μg L−1) were determined. Weight gain, specific growth rate (SGR), body mass, relative condition factor and survival were evaluated. The water quality was influenced by the live food and stocking densities. Fish fed M. minuta showed better weight gain, specific growth ratio (SGR), biomass gain, relative condition factor and survival than in the other treatment. Artemia sp. showed no improved influence on the larvae performance subjected to different treatments. The beneficial role in growth and survival of leaf fish larva when fed with M. minuta is discussed.

Effect of starvation on growth, biochemical, hematological and non-specific immune parameters in two different size groups of grey mullet, Mugil cephalus (Linnaeus, 1758)

The present research aims to shed lights on some physiological parameters induced by food deprivation in grey mullet Mugil cephalus charaterized with different weights and sizes (A and B). Growth (final weight, weight gain percent (WG%), specific growth ratio (SGR), condition factor (CF) and hepatosomatic index (HSI)), hematological (hematocrit, hemoglobin, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), Red Blood Counts (RBCs) and White Blood Counts (WBCs) and mean corpuscular haemoglobin concentrations (MCHC)), biochemical (crude protein, crude lipid, ash and moisture, serum total protein, glucose, cholesterol, cortisol, aspartate aminotransferase (AST) and alanine aminotransferase (ALT)) and immunological (lysozyme activity) parameters in two different sized grey mullet (size A: 9.52±0.98cm, total length, 7.46±1g and size B: 12.05±0.86cm, total length, 21.01±3.07g weight) in a 30day starvation period compared to fed fish were measured. Throughout the experiment, blood hematocrit, hemoglobin, MCV, MCHC, MCH and RBC, AST, ALT were not affected upon starvation in significant manner. As for the starved group, CF, HIS and WBCs levels were recorded in significant manner than fed one in both different sized fish. Moreover, since day 20th onwards, serum lysozyme activity was increased significantly in starved grey mullet characterized with two different sizes. The present results indicate that fasting in the starved group, size A can decrease significantly growth parameters, crude lipid, carcass ash, cholesterol levels, and cortisol and glucose concentrations.

The effects of dietary carbohydrate on the growth, antioxidant capacities, innate immune responses and pathogen resistance of juvenile Black carp Mylopharyngodon piceus.

The present study was focused on the growth, antioxidant capacities, innate immune responses and pathogen resistance in juvenile Black carp Mylopharyngodon piceus fed with graded levels of dietary carbohydrate (CHO) (0.6, 106.5, 194.3, 288.4, 379.1 and 473.8gkg(-1)) for 9 weeks. Results showed that highest weight gain and special growth ratio was obtained at 288.4gkg(-1) dietary CHO. And adequate dietary CHO content (288.4gkg(-1)) could significantly increase the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gpx), promote reduced glutathione (GSH) content and then increase the total antioxidant capacities (TAOC) in the liver of M.piceus. However, the malondialdehyde (MDA) levels in the fish liver could be significantly aggravated by excessive dietary CHO. Serum cortisol (COL) levels could be significantly increased in juvenile Black carp M.piceus fed with 379.1gkg(-1) dietary CHO compared with CHO-deficient diets. Activities of alanine transaminase (GPT) and aspartate transaminase (GOT) were both decreased in the serum of juvenile Black carp M.piceus fed with 194.3gkg(-1) dietary CHO compared with CHO-deficient diets (0.6 and 106.5gkg(-1)) or CHO-excess diets (379.1 and 473.8gkg(-1)). In addition, 288.4gkg(-1) dietary CHO could significantly up-regulate the mRNA expression levels of hepcidin (HEPC), natural resistance-associated macrophage protein (NRAMP), tumor necrosis factor-α (TNF-α) and interferon (IFN), lysozyme (LYZ) and complement component 3 (C3) in the blood and liver samples of juvenile Black carp M.piceus compared with the CHO-deficient diets (0.6 and 106.5gkg(-1)). Moreover, 288.4gkg(-1) dietary CHO could also enhance the contents of C3 and plasma nitrogen monoxide (NO), and increase the activities of LYZ and total nitric oxide synthase (t-NOS) in the serum compared with the CHO-deficient or CHO-excess diets. Furthermore, the survival rates were also increased by adequate dietary CHO (194.3 and 288.4gkg(-1)) fed to juvenile Black carp M.piceus after infection with Aeromonas hydrophila. In conclusion, these results suggest that adequate dietary CHO (288.4gkg(-1)) could increase growth, reduce oxidative stress, enhance innate immune responses, improve the health states and then promote disease resistance in juvenile Black carp M.piceus.