Effect of stocking density on growth performance,serum biochemical parameters,and muscle texture properties of genetically improved farm tilapia, <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

The objective of this study was to assess the effects of stocking density on growth performance, serum biochemical parameters, and muscle texture properties of genetically improved farmed tilapia (Oreochromis niloticus, GIFT). Juvenile GIFT with an average initial weight of 12.54?±?0.45 g (mean?±?SD) were randomly stocked in 16 tanks (80 L) in a recirculation aquaculture system at four densities of 10 (D1), 20 (D2), 30 (D3), and 40 (D4) fish per tank for 56 days, with quadruplicate for each density. There were no significant differences in water temperature among the four treatments (P?>?0.05). D4 had the significantly lowest dissolved oxygen content (5.52 vs 5.69–6.09 mg L^?1) (P?>?0.05) and pH (6.63 vs 6.87–7.20) (P?<?0.05). NO₂-N and NH₄-N concentrations significantly increased with increasing stocking density (P?<?0.05). Weight gain (WG) and specific growth rates (SGR) decreased with increasing stocking density. The lowest WG (617.20 vs 660.45–747.06%), SGR (3.52 vs 3.62–3.81% day^?1), and highest feed conversion ratio (1.68 vs 1.53–1.58) were observed in D4. Fish at D4 had significantly lower condition factor (3.11 vs 3.29–3.37%) and survival rate (91.25 vs 97.50%) than those from D1 and D2 (P?<?0.05). With increasing stocking density, serum total cholesterol, triglyceride, and total protein concentrations decreased (P <?0.05) and aspartate aminotransferase and alanine aminotransferase activities increased (P <?0.05). D4 fish had higher moisture content (78.80 vs 76.97%) and lower crude protein content (18.14 vs 19.39%) in muscle than D1 fish (P?<?0.05). Compared to D1 and D2, D3 and D4 had lower muscle hardness (1271.54–1294.07 vs 1465.12–1485.65 g), springiness (0.62–0.65 vs 0.70–0.72), gumminess (857.33–885.32 vs 1058.82–1079.28 g), and chewiness (533.04–577.09 vs 757.53–775.69 g) (P <?0.05). High stocking density resulted in growth inhibition, declines in flesh quality, and disturbance to several serum biochemical parameters.     

Dietary protein and carbohydrate requirement of juvenile Hawaiian limpet (<Emphasis Type="Italic">Cellana sandwicensis</Emphasis> Pease, 1861) fed practical diet

This study was conducted to evaluate dietary protein and carbohydrate requirement of juvenile Hawaiian limpets Cellana sandwincensis. A total of 64 juvenile limpets (3.12 ± 0.86 g) were fed five different dietary protein levels ranging from 270 to 470 g kg^?1 for 90 days. Carbohydrate and lipid levels were held constant at 180 and 49.7 g kg^?1, respectively. Weight gain and growth rates of the animals did not differ significantly (P > 0.05) among the protein levels ranging from 270 g kg^?1 (0.30 % day^?1) to 470 g kg^?1 (0.23 % day^?1). Next, opihi were fed four diets with protein levels from 210 to 500 g kg^?1 with a constant carbohydrate level at 120 g kg^?1. Weight gain and specific growth rates of opihi increased with increasing dietary protein from 210 to 350 g kg^?1, and significantly (P < 0.05) decreased at the 500 g kg^?1 diet. Highest weight gain, growth rates, and protein efficiency ratio were achieved at 350 g kg^?1. Elevated carbohydrate levels (180–370 g kg^?1) produced a significant difference (P < 0.05) in growth. The fastest growth rates of animals were obtained with 270 g kg^?1 (0.27 % day^?1) and 320 g kg^?1 (0.26 % day^?1). The weight gain of animals fed 180 and 370 g kg^?1 carbohydrate diets were significantly (P < 0.05) lower than those of animals fed 270 and 320 g kg^?1. We conclude that about 350 g kg^?1 protein and 320 g kg^?1 carbohydrate levels could be used for opihi.     

Growth performance and immune responses of gibel carp, <Emphasis Type="Italic">Carassius auratus gibelio</Emphasis>, fed with graded level of rare earth-chitosan chelate

A 12-week feeding trail was conducted to assess the effect of rare earth-chitosan chelate (RECC) on growth performance and immune responses of gibel carp, Carassius auratus gibelio. Isonitrogenous and isolipid experimental diets were supplemented with graded levels of rare earth-chitosan chelate (RECC 0, 0.8, 4 and 8 g Kg^?1). A total of 720 gibel carps (initial body weight about 14.32 g) were divided randomly into four groups with six replicates, respectively. Fish were fed with the experimental diets three times every day. At the end of the feeding trail, the survival rate was higher than 96 %. Weight gain rate and specific growth rate (SGR) significantly increased with RECC supplementation up to 0.8 g Kg^?1 (P < 0.05) and tended to decline at higher supplementation levels, while feed conversion ratio was not significantly different between groups (P > 0.05). Based on broken-line regression analysis of SGR, the optimum dietary RECC was estimated to be 0.71 g Kg^?1 of the diet. Condition factor and viscerosomatic index were not significantly affected by RECC (P > 0.05), while hepatosomatic index in the group fed with 0.8 g Kg^?1 RECC (3.45 ± 0.10 %) was significantly lower than in other groups (P < 0.05). Plasma ALT was significantly affected by RECC (P < 0.05), while AST was not. Plasma total protein and albumin were increased with RECC supplementation up to 0.8 g Kg^?1 and decreased significantly at higher supplementation levels (P < 0.05). RECC supplementation significantly decreased plasma urea and glucose concentration and increased plasma creatinine concentration significantly (P < 0.05). Respiratory burst activity of phagocytes and myeloperoxidase activity were not significantly different between groups, while superoxide dismutase activity and nitrogen monoxide concentration were increased with the increasing level of RECC in the diets. In conclusion, RECC could enhance growth performance and improve immunity of gibel carp.     

Effect of dietary chitosan on growth performance,hematological parameters,intestinal histology and stress resistance of Caspian kutum (<Emphasis Type="Italic">Rutilus frisii kutum</Emphasis> Kamenskii, 1901) fingerlings

This study was conducted to investigate the effects of dietary chitosan on growth performance, hematological parameters, intestinal histology, stress resistance and body composition in the Caspian kutum (Rutilus frisii kutum, Kamenskii, 1901) fingerlings. Fish (1.7 ± 0.15 g) were fed diets containing chitosan at different levels (0, 0.25, 0.5, 1 and 2 g kg^?1 diet) for a period of 60 days. Results showed that the feed conversion ratio significantly decreased in fish fed diet containing 1 g kg^?1 of chitosan compared to the other groups (P < 0.05), but there were no significant differences between treatments in terms of specific growth rate and condition factor (P > 0.05). Leukocyte increased in fish fed diet containing 2 g kg^?1 of chitosan compared to the other groups (P < 0.05). Lymphocytes, eosinophils and neutrophils did not significantly change among dietary treatments (P > 0.05). Also, the chitosan supplementation did not affect the whole-fish body composition (P > 0.05). Light microscopy demonstrated that the intestinal villus length increased in fish fed diet containing 1 g kg^?1 of chitosan compared to control group (P < 0.05). While 11 and 13 ‰ salinity and 30 °C thermal stress had no effect, 1 g kg^?1 of chitosan (P < 0.05) showed highest survival rate (70 %) in 34 °C thermal stress. The results showed that chitosan in the diet of the Caspian kutum fingerlings could improve feed conversion ratio, the nonspecific defense mechanisms and resistance to some of the environmental stresses.     

Demographic and competition studies on <Emphasis Type="Italic">Brachionus ibericus</Emphasis> and <Emphasis Type="Italic">Proales similis</Emphasis> in relation to salinity and algal (<Emphasis Type="Italic">Nannochloropsis oculata</Emphasis>) density

We isolated the rotifers Brachionus ibericus and Proales similis from the sediment of shrimp tanks and studied their individual demographic characters and competition between them at two food levels (0.25?×?10⁶, 1.00?×?10⁶ cells ml^?1 of Nannochloropsis oculata at 25 °C) and salinities ranging from 10 to 30‰. Our hypothesis was that growth rates would be higher with increasing food levels and salinities. Observations were taken twice a day for life table studies and daily once for population growth experiments. Using survivorship and fecundity data, we derived various life history variables. Although the average life span (7.6?±?0.4 days) and gross reproductive rate (33.8?±?2.9 neonate female^?1 day^?1) of B. ibericus were higher than those of P. similis (average life span 5.4?±?0.6 days and gross reproductive rate 13.0?±?0.6 neonate female^?1 day^?1), the population growth experiments showed that P. similis had higher r values (0.32?±?0.005 day^?1) than B. ibericus (0.23?±?0.002 day^?1) at 1.0?×?10⁶ cells ml^?1 of N. oculata. The rotifer P. similis was more adversely affected due to the presence of B. ibericus than vice versa. The data are important for developing techniques for a large-scale culture of these rotifers as food in aquaculture.     

Use of thraustochytrid <Emphasis Type="Italic">Schizochytrium</Emphasis> sp. as source of lipid and fatty acid in a formulated diet for abalone <Emphasis Type="Italic">Haliotis asinina</Emphasis> (Linnaeus) juveniles

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day^?1; DISL: 265 μm day^?1) and Diet 2 (SGR: 5.2 % BW day^?1; DISL: 255 μm day^?1). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet.     

The effects of starvation on fast-start escape and constant acceleration swimming performance in rose bitterling (<Emphasis Type="Italic">Rhodeus ocellatus</Emphasis>) at two acclimation temperatures

To investigate the effects of starvation and acclimation temperature on the escape ability of juvenile rose bitterling (Rhodeus ocellatus), we measured the fast-start escape and constant acceleration swimming performance of fish fasted for 0 (control), 1 and 2 weeks and half-lethal periods (6 or 4 weeks) at two temperatures (15 and 25 °C). Fish acclimated at a high temperature exhibited shorter response latency (R), higher maximum linear velocity (V _max) and longer escape distance during escape movement (D _120ms) than those at the low temperature. Starvation resulted in a significant decrease in V _max and D _120ms at either low or high temperature and a significant increase in R at only the high temperature in the half-lethal period groups (P < 0.05). The relationship between V _max (Y, m s^?1) and starvation time (X, week) was Y ₁₅ = ?0.062X + 1.568 (r = ?0.665, n = 36, P < 0.001) at low temperature and Y ₂₅ = ?0.091X + 1.755 (r = ?0.391, n = 40, P = 0.013) at high temperature. The relationship between U _cat (Y, cm s^?1) and starvation time (X, week) was Y ₁₅ = ?1.649X + 55.418 (r = ?0.398, n = 34, P = 0.020) at low temperature and Y ₂₅ = ?4.917X + 62.916 (r = ?0.793, n = 33, P < 0.001) at high temperature. The slopes of equations showed a significant difference between low and high temperature (F _1,63 = 9.688, P = 0.003), which may be due to the different energy substrate utilization when faced with food deprivation at different temperatures.     

Growth,hematological and biochemical indices of common carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> fed diets containing corn gluten meal

The effects of replacing fish meal (FM) with corn gluten meal (CGM) on growth and physiological performance were evaluated in common carp (Cyprinus carpio). Six experimental diets were formulated by substituting 0 (control), 20, 40, 60, 80, and 100% CGM protein for FM protein. The concentrations of dietary protein in the experimental diets were 27.8–29% and the P:E ratios were 14.7–15.46 mg/kJ. Eighteen fish with an initial weight of 13.5?±?0.1 g were allocated to each of 18 circular tanks (450 L) to give triplicate groups for each dietary treatment. The fish were fed to satiation for 8 weeks. At the end of the feeding trial, growth indices, body proximate composition, and hematological and biochemical parameters were measured. Blood samples were taken from six fish in each tank. Final weight and total length were significantly higher in fish fed 100% CGM (27.8?±?1.2 g and 11.9?±?0.3 cm) than for those fed the control (22.7?±?1.4 g and 10.9?±?0.5 cm) or 20% CGM (22.3?±?1.2 g and 11?±?0.4 cm) diets. No effect of FM replacement by CGM was observed for condition factor or hepatosomatic index (P?>?0.05). The highest value of protein productive value (14.31?±?0.65) was observed in fish fed 20% CGM (P?<?0.05). There were no significant differences in percentage body moisture and fat, but percentages of protein and ash were significantly different among experimental groups; the highest values of protein (15.6?±?0.24%) and ash (3.01?±?0.26%) were recorded in fish fed 40% CGM. For hematological parameters, the highest number of white blood cells (4.1?±?0.1?×?10³ mm^?3) was observed in fish fed 100% CGM (P?<?0.05). In addition, the highest hematocrit (42.1?±?0.7%) and triglyceride (294.11?±?23.82 mg dl^?1) were seen in fish fed the diet containing 40% CGM, while 80% CGM gave the highest cholesterol level (204.44?±?9.0 mg dl^?1; P?<?0.05). Replacement of FM with CGM had no negative effects on growth and physiological parameters of common carp fingerlings in this short (8 weeks) trial, suggesting that it may be feasible to replace FM with CGM in diets formulated for juvenile common carp.     

Effects of nucleotides on growth performance,immune response,disease resistance and intestinal morphology in shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> fed with a low fish meal diet

Nucleotides (NT) are widely used as an immunostimulant in aquaculture. A 10-week feeding trial was conducted to evaluate the effects of dietary NT on the growth performance, immune response, disease resistance and intestinal morphology of the Pacific white shrimp Litopenaeus vannamei (initial mean body weight: 0.39 ± 0.00 g). Five isolipidic (about 7 % crude lipid) and isonitrogenous (about 39 % crude protein) practical diets were supplemented with graded levels of NT (0, 60, 90, 120 and 1200 mg kg^?1), respectively. These diets were named as N1, N2, N3, N4 and N5. Each diet was randomly fed to six tanks of shrimps, and each tank contained 40 shrimps. The shrimps were fed four times daily (07:00, 11:00, 16:00 and 21:00 h). The results showed that there were no significant differences in survival, final weight, specific growth rate, feed intake, feed conversion ratio and whole-body compositions among all the treatments (P > 0.05). Shrimps fed the control diet had the significantly lowest activities of superoxide dismutase, total nitric oxide synthase and lysozyme (P < 0.05). However, those parameters increased when dietary NT increased from 60 to 120 mg kg^?1 and decreased as inclusion level increased to 1200 mg kg^?1 (P < 0.05). The cumulative mortality of the shrimps challenged with Vibrio parahaemolyticus was significantly higher in the treatments without dietary NT supplementation than those in treatments with dietary NT (≥90 mg kg^?1) (P < 0.05). The jejunum wall thickness in shrimps fed the control diet was significantly lower than that in the treatments of N2, N3 and N4 (P < 0.05). For the villus height, the highest value (49.29 µm) was found in N3. In summary, the present study showed that 90 mg kg^?1 of dietary NT is the optimum dietary level for good gut health, immune response and disease resistance of Pacific white shrimp fed a diet with 18 % fish meal.     

The effects of starvation and re-feeding on growth and swimming performance of juvenile black carp (<Emphasis Type="Italic">Mylopharyngodon piceus</Emphasis>)

We investigated the effects of starvation and re-feeding on growth and swimming performance and their relationship in juvenile black carp (Mylopharyngodon piceus). We measured the specific growth rate (SGR), resting metabolic rate (RMR) and constant acceleration test speed (U _CAT, the maximum swimming speed at exhaustion by constant acceleration test with 0.1667 cm s^?2 rate) in a treatment group (21 days of starvation then 21 days of re-feeding) and control group (routine feeding) (n = 20). Starvation resulted in a 17 % decrease in body mass of black carp (P < 0.05). After 21 days of re-feeding, body mass was greater than that of pre-starvation but still less than that of the control group at 42 days. During the re-feeding phase, the SGR of the treatment group was higher than that of the control group (P < 0.05). Starvation resulted in a significant decrease in the RMR and U _CAT. After 21 days of re-feeding, both the RMR and U _CAT recovered to the pre-starvation levels. In the control group, individual juvenile black carp displayed strong repeatability of the RMR and U _CAT across the measurement periods (P ≤ 0.002). In the treatment group, RMR showed significant repeatability between pre-starvation and re-feeding (P = 0.007), but not between pre-starvation and starvation or between starvation and re-feeding. U _CAT showed significant repeatability between pre-starvation and starvation (P = 0.006) and between pre-starvation and re-feeding (P = 0.001), but not between starvation and re-feeding. No correlation or only a weak correlation was found between any two variables of RMR, U _CAT and SGR, whereas the increment of the U _CAT (ΔU _CAT) was negatively correlated with that of SGR during the starvation phase (r = ?0.581, n = 20, P = 0.007) and re-feeding phase (r = ?0.568, n = 20, P = 0.009). This suggested that within individual black carp, there is a trade-off between growth and maintenance (or development) of swimming performance under food-limited conditions.     

Effects of salinity,stocking density,and algal density on growth and survival of Iwagaki oyster <Emphasis Type="Italic">Crassostrea nippona</Emphasis> larvae

To determine the optimal salinity, stocking density, and algal density for hatchery culture of the Iwagaki oyster Crassostrea nippona larvae, three experiments with salinities of 14, 18, 22, 26, 30, and 34 practical salinity unit (PSU); stocking densities of 0.5, 1, 2, 4, 8, and 12 larvae ml^?1; and algal densities of 10, 20, 40, and 100?×?10³ cells ml^?1 were designed, which included the developmental stages from newly hatched D-larvae to pediveligers. Results showed that larval growth of C. nippona was the fastest at a salinity of 26 PSU, and when salinity was adjusted to a level that was lower or higher than this salinity, survival and growth rate of larvae declined (P <?0.05), resulting both in a decreased mean shell length and a high mortality. Larval growth decreased significantly with increasing stocking density. Larvae reared at 4 larvae ml^?1 had the smallest shell length (198.9 μm) and lowest survival rate (7.9%), whereas larvae reared at 0.5 larvae ml^?1 had the largest shell length (245 μm) and highest survival rate (66.3%) on day 13. And the shell length of larvae reared at 0.5 and 1 larvae ml^?1 was significantly (P?<?0.05) larger than the values in other treatments, except those reared at 2 larvae ml^?1 (P?>?0.05). When feeding the single-algal diet of Isochrysis galbana (clone T-ISO), the shell length of larvae increased markedly as the algal density was increased. Larvae reared at the highest algal density (100?×?10³ cells ml^?1) had the largest mean shell length; however, under the conditions of our experiment, there was no significant difference (P?>?0.05) in growth and survival rates between the treatments at algal densities of 40?×?10³ and 100?×?10³ cells ml^?1. For a large-scale culture, based on the results of this study, a salinity of 26 PSU, stocking density of 0.5–1 larvae ml^?1, and algal density of 40?×?10³ cells ml^?1 are recommended for an early development of C. nippona.     

Physiological response,blood chemistry profile and mucus secretion of red sea bream (<Emphasis Type="Italic">Pagrus major</Emphasis>) fed diets supplemented with <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> under low salinity stress

Environmental stressors caused by inadequate aquaculture management strategies suppress the immune response of fish and make them more susceptible to diseases. Therefore, efforts have been made to relieve stress in fish by using various functional feed additives in the diet, including probiotics. The present work evaluates the effects of Lactobacillus rhamnosus (LR) on physiological stress response, blood chemistry and mucus secretion of red sea bream (Pagrus major) under low salinity stress. Fish were fed four diets supplemented with LR at [0 (LR0), 1 × 10² (LR1), 1 × 10⁴ (LR2) and 1 × 10⁶ (LR3) cells g^?1] for 56 days. Before stress, blood cortisol, urea nitrogen (BUN) and total bilirubin (T-BIL) showed no significant difference (P > 0.05), whereas plasma glucose and triglyceride (TG) of fish-fed LR2 and LR3 diets were significantly lower (P < 0.05) than those of the other groups. Plasma total cholesterol (T-CHO) of fish-fed LR3 diet was significantly (P < 0.05) lower than that of the other groups. Furthermore, total plasma protein, mucus myeloperoxidase activity and the amount of mucus secretion were significantly enhanced in LR-supplemented groups when compared with the control group (P < 0.05). After the application of the low salinity stress test, plasma cortisol, glucose, T-CHO and TG contents in all groups showed an increased trend significantly (P < 0.01) compared to the fish before the stress challenge. However, plasma total protein and the amount of secreted mucus showed a decreased trend in all groups. On the other hand, BUN, T-BIL and mucus myeloperoxidase activity showed no significant difference after exposure to the low salinity stress (P > 0.05). In addition, the fish that received LR-supplemented diets showed significantly higher tolerance against low salinity stress than the fish-fed LR-free diet (P < 0.05). The physiological status and the detected immune responses, including total plasma protein and mucus myeloperoxidase activity in red sea bream, will provide a more comprehensive outlook of the effects of probiotics to relieve stress in fish.     

The changes in cortisol and expression of immune genes of GIFT tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> (L.) at different rearing densities under <Emphasis Type="Italic">Streptococcus iniae</Emphasis> infection

The present study was conducted to investigate the effects of stocking density on serum cortisol (COR) levels and expression of immune genes in the head kidney of juvenile GIFT tilapia (Oreochromis niloticus) after Streptococcus iniae (S. iniae) infection. Juveniles (2700) were distributed into 30 tanks at five stocking densities (150, 300, 450, 600 and 750 g/m³), and each treatment had six replicates. After a 45-day feeding trial, a S. iniae challenge study was conducted for 96 h. Differences in mortality, serum COR and gene expression of C-type lysozyme, heat-shock protein 70 (HSP70), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were analyzed. The levels of serum COR at all infected treatments were significantly higher compared with the levels of pre-infection (P < 0.05). At 96 h post-infection, serum COR levels of high stocking densities (600 and 750 g/m³) were significantly higher than those of low-density groups (P < 0.05); the mRNA levels of C-type lysozyme, HSP70, IL-1β, TNF-α and IFN-γ were significantly lower in tilapia reared at 600 g/m³ group than in those reared at 300 g/m³ group (P < 0.05). Fish reared in high-density treatments (600 and 750 g/m³) exhibited significantly higher post-challenge mortality (43.3 and 40.0 %) at 96 h following S. iniae infection, and it was significantly higher than other groups (P < 0.05). The data suggest that when living in high stocking density, GIFT tilapia showed decrease in immune capability, together with increased serum COR and susceptibility to S. iniae.     

Enhancing the dietary value of palm oil in the presence of lysolecithin in tiger shrimp, <Emphasis Type="Italic">Penaeus monodon</Emphasis>

The effect of four iso-nitrogenous and iso-lipidic diets containing soy lecithin and lysolecithin with fish oil (sardine) and palm oil on growth, digestibility, and fatty acid composition of tail muscle and non-muscle portions of tiger shrimp, Penaeus monodon, was evaluated. Shrimp fed with lysolecithin diets had significantly (P?<?0.05) higher daily growth coefficient values (1.40–1.45% day^?1) than those fed with soylecithin containing diets (1.32–1.37% day^?1). Correspondingly, lysolecithin-supplemented diets showed significantly higher (P?<?0.05) apparent digestibility coefficients (ADC) of fatty acids with both the oils due to higher emulsification ability of small micelle forming by lysolecithin. However, there were no significant differences in survival and FCR among all treatments. The fatty acid composition of the test diets reflected to a certain extent in the fatty acid composition of the muscle and non-muscle portions of shrimp. Arachidonic, eicosapentaenoic, and docosahexaenoic acid contents of muscle and non-muscle portions of shrimp were significantly (P?<?0.05) higher in lysolecithin-supplemented diet compared to soylecithin-supplemented diet. The present results suggest that lysolecithin improved the fatty acid digestibility with its high emulsification properties that reflected in better performance by improving dietary value of palm oil.     

Effect of nitrite exposure on oxygen-carrying capacity and gene expression of <Emphasis Type="Italic">NF-κB</Emphasis>/<Emphasis Type="Italic">HIF-1α</Emphasis> pathway in gill of bighead carp (<Emphasis Type="Italic">Aristichthys nobilis</Emphasis>)

Nitrite (NO₂^?) contamination of water can severely impact the health of aquatic life and is a major concern for commercial aquaculture. In order to study the effect of nitrite on Aristichthys nobilis, we investigated the oxygen-carrying capacity, NF-κB/HIF-1α pathway, and the gill tissue structure under nitrite stress. In the current study, bighead carp (initial weight 180.05?±?0.092 g) were exposed to nitrite (48.634 mg/L) for 96 h and then for 96 h recovery test. After nitrite exposure for 6 h, hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-κB (NF-κB) mRNA expression increased significantly in the gill of bighead carp (P?<?0.05). After nitrite exposure for 12 h, hemoglobin (Hb) and methemoglobin reductase (MHBR) content in blood decreased significantly (P?<?0.05); TLR4 mRNA expression increased significantly (P?<?0.05). After nitrite exposure for 24 h, methemoglobin (MetHb) content increased significantly (P?<?0.05). After recovery test, all the indicators except TLR4 mRNA expression level recovered to initial level. In conclusion, nitrite exposure can affect hemoglobin dynamics, as oxidization of nitrite by hemoglobin results in the reduction of Hb to MetHb leading to hypoxia and nitrite exposure can also result into gill tissue damage. In the face of nitrite exposure, NF-κB and HIF-1α mRNA expression level increased immediately to protect the body from oxidative damage and eased hypoxic condition caused by nitrite. It was also observed that nitrite damage is recoverable in Aristichthys nobilis, but it may be need more than 96 h.     

Biofloc management with different flow rates for solids removal in the <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> BFT culture system

Different water flows for solids removal in the Litopenaeus vannamei BFT system were evaluated. One control (no solids removal) and two treatments using different water flows, high (3945 L h^?1—HF) and low (1750 L h^?1—LF), were used with no water replenishment after each process, and the total dry weight of the solids was measured. L. vannamei (0.18 ± 0.06 g; 350 individuals m^?2) were stocked in 35-m^?3 tanks. For 17 weeks, the physical and chemical parameters were maintained within the recommended. To keep the total suspended solids concentrations at approximately 500–600 mg L^?1, clarifying was performed. The average water volume flowed by clarifiers was significantly different (p < 0.05) between HF (205 ± 34 m³) and LF (114 ± 24 m³). There was a significant decrease (p < 0.05) in the final tank volume in HF (28.09 ± 0.92 m³) and LF (28.62 ± 1.38 m³) due to the clarifying. Before clarifying (initial sample) and at the end of experiment (final sample) were not significantly different (p > 0.05) for crude protein, moisture or ash. The crude lipid of the LF in the final period was significantly lower (p < 0.05) compared to others in both periods. The survival, productivity and food conversion ratio were significantly better (p < 0.05) in the HF and LF treatments compared to those of the control. The best shrimp performance was obtained with solids removal. The lower flow in the clarifier facilitated particle settling, allowing adjustment of the flow.     

<Emphasis Type="Italic">Virgibacillus proomii</Emphasis> and <Emphasis Type="Italic">Bacillus mojavensis</Emphasis> as probiotics in sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>) larvae: effects on growth performance and digestive enzyme activities

This study examined the effects of two probiotics (Virgibacillus proomii and Bacillus mojavensis) on the digestive enzyme activity, survival and growth of Dicentrarchus labrax at various ontogenetic stages in three separate experiments. These probiotics were incorporated as single or mixed into fish feed for a period of 60 days. The growth parameters, proximate composition of whole body, digestive enzymes and gut microbiology were monitored at regular. The increments in length and weight and the survival were significantly higher (P < 0.05), and the values of food conversions were significantly lower (P < 0.05) in fishes fed the probiotic. The administration of V. proomii and B. mojavensis in diet resulted in an increase (P > 0.05) in body ash and protein content and in the specific activity of phosphatase alkaline and amylase in the digestive tract of all the fishes. V. proomii and B. mojavensis persisted in the fish intestine and in the feed in high numbers during the feeding period (group 1: 5.8 × 10⁴ CFU/ml, group 2: 9.6 × 10⁴ CFU/ml, and group 3: 9.8 × 10⁴ CFU/ml day 60). The two probiotics V. proomii and B. mojavensis were adequate for improved growth performance and survival and for healthy gut microenvironment of the host.     

Corn gluten meal in pacu <Emphasis Type="Italic">Piaractus mesopotamicus</Emphasis> diets: effects on growth,haematology, and meat quality

Corn gluten meal (CGM) has a high protein content and absence of antinutrients. However, it has high levels of carotenoids that can cause a yellowing of fish fillets and impair further commercialisation. Graded levels of CGM were incorporated in pacu diets to replace soybean meal (SM) protein. The experimental diets were formulated to be isonitrogenous (220 g kg^?1 digestible protein) and isoenergetic (13.4 MJ kg^?1 digestible energy) with 0, 25, 50, 75, and 100 % replacement of SM protein by CGM protein over a 60-day period. One hundred fish (32.79 ± 3.43 g) were randomly distributed in 20 experimental cages (70 L) placed within five (1000 L) aquaria with continuous water renewal. The experimental design was completely randomised with five treatments and four replicates. A quadratic effect (P < 0.05) was observed for fillet and carcass yields, feed conversion ratio, weight gain, and specific growth rate, with the optimum values for replacement of SM protein by CGM protein estimated as 21.95, 29.13, 30.94, 37.71, and 38.75 %, respectively. There were no differences (P > 0.05) for blood parameters, proximal composition, water-holding capacity, pH, lipid oxidation, and a* value of fillets. The L* and b* values of fillets showed differences (P < 0.05). Replacement between 21.95 and 38.75 % of SM protein by CGM protein (5.37 and 9.48 % of inclusion in the diet) improves the growth performance and body yield of pacu juveniles without altering blood parameters or affecting the fillet quality.     

Gastrointestinal and hepatic enzyme activities in juvenile silvery-black porgy (<Emphasis Type="Italic">Sparidentex hasta</Emphasis>) fed essential amino acid-deficient diets

As amino acids (AAs) are vital molecules in the metabolism of all living organisms and are the building blocks of enzymes, a 6-week feeding trial was conducted for determining the influence of dietary essential amino acid (EAA) deficiencies on pancreatic, plasma, and hepatic enzyme activities in silvery-black porgy (initial weight 4.7?±?0.01 g) juveniles. Eleven isoproteic (ca. 47%) and isoenergetic (ca. 20.5 MJ kg^?1) diets were formulated including a control diet, in which 60% of dietary nitrogen were provided by intact protein (fish meal, gelatin, and wheat meal) and 40% by crystalline AA. The other 10 diets were formulated by 40% reduction in each EAA from the control diet. At the end of the experiment, fish fed with threonine-deficient diet showed the lowest survival rate (P?<?0.05), whereas growth performance decreased in fish fed all EAA-deficient diets, although the reduction in body growth varied depending on the EAA considered. Pancreatic enzymes (trypsin, lipase, α-amylase, and carboxypeptidase A) activities significantly decreased in fish fed the EAA-deficient diets in comparison with fish fed the control diet (P?<?0.05). Fish fed with the arginine-deficient diet had the highest plasma and liver alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels (P?<?0.05). Plasma and liver lactate dehydrogenase and superoxide dismutase showed the highest and lowest values, respectively, in fish fed the arginine and lysine-deficient diets (P?<?0.05). Plasma metabolites were significantly affected by dietary EAA deficiencies (P?<?0.05). The results of this study suggesting dietary EAA deficiencies led to reduction in growth performance as well as pancreatic and liver malfunction. Furthermore, arginine and lysine are the most limited EAA for digestive enzyme activities and liver health in silvery-black porgy.     

Dietary supplementation of yeast (<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>) improves growth,stress tolerance,and disease resistance in juvenile Nile tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>)

The yeast Saccharomyces cerevisiae is one of the commonest probiotics incorporated in aquafeeds. An 84-day feeding trial was conducted to evaluate the effects of varying dietary inclusions of S. cerevisiae, 0% (control), 3% (YF3), 5% (YF5), and 7% (YF7), on growth, stress tolerance, and disease resistance in juvenile (body mass ~?21 g) Nile tilapia (Oreochromis niloticus). Fish were randomly distributed in groups of 20 into 12 1-m³ hapas and fed isoenergetic (~?17 kJ g^?1 gross energy) and isonitrogenous (~?300 g kg^?1 crude protein) diets at 3% of their bulk weight daily. Specific growth rates were significantly higher for the yeast-fed fish (0.77–0.78% day^?1) than for the control fish (0.60% day^?1) and resulted in significantly higher mean final weights for the yeast-treated groups. Protein and lipid retention efficiencies were also significantly higher in the yeast-fed fish than in the control group. In subsequent stress challenge trials, the yeast-fed fish had greater tolerance to acute heat as well as hypoxia exposure than the control fish. Survival rates of the yeast-treated groups following sudden exposure to elevated water temperature (40 °C) ranged from 82.5 to 100% compared to 15% for the control. Mean survival rates following a 24-h hypoxia exposure were also generally significantly higher for the yeast-fed fish. The probiotic groups recorded a relative percent survival (RPS) of 75% after a 14-day Aeromonas hydrophila infection challenge. The results of this study indicate that S. cerevisiae as an additive in Nile tilapia diets has beneficial impacts on growth, stress tolerance, and disease resistance.