Dietary potassium requirement of juvenile grass shrimp Penaeus monodon

ABSTRACT: A feeding trial was conducted to estimate the minimal dietary potassium (K) requirement for juvenile grass shrimp Penaeus monodon . Purified diets with seven levels (0, 0.3, 0.6, 0.9, 1.2, 1.5, 2.0 g/100 g) of supplemental potassium were fed to P. monodon (mean initial weight 0.75 ± 0.01 g) for 8 weeks. Each diet was fed to three replicate groups of shrimp. The rearing water contained 360 mg/L potassium. Weight gain and protein efficiency ratio (PER) of shrimp improved as dietary potassium supplementation level increased up to 1.5 g K/100 g diet and thereafter declined significantly ( P < 0.05). Feed efficiency (FE) of shrimp also showed a similar trend. However, whole body K concentration of the shrimp kept an increasing trend up to 2.0 g K/100 g diet. Analysis of the weight gain (percent) and PER of the shrimp by polynomial regression indicate that the minimal dietary potassium requirement in growing P. monodon is approximately 1.2 g/100 g.     

Interaction of Salinity and Feed Protein Level on Growth of Penaeus vannamel

An intensive 42-day growth trial conducted in ourdoor tanks with Penaeus vannamei (stocking weight of 5.3g, density of 30/m²) indicated that there was a significant interaction between salinity and protein level of the feed. In 46 ppt water, shrimp fed feed containing 45% protein grew faster (2.98%/day) than shrimp fed 35 and 25% protein rations (2.84 and 2.73%/day, respectively). At 12 ppt, growth of shrimp fed 35% feed was faster (3.23%/day) than growth of shrimp fed 25% protein feed (3.07%/day). Shrimp fed the 45% protein feed did not grow faster 3.14%/day) than shrimp fed 35 an 25% protein feeds. At each protein level, growth at 12 ppt was greater than at 46ppt. Survival was not affeted by either salinity or feed protein level and averaged 86%. Results indicate that nutritional requirements vary with culture salinity and suggest that use of higher protein feeds under hypersaline culture conditions may produce higher yields.     

Effects of dietary chitosan on growth,survival and stress tolerance of postlarval shrimp,Litopenaeus vannamei

The effect of chitosan, a polymer of glucosamine obtained by the deacetylation of chitin, on growth, survival and stress tolerance was studied in postlarval Litopenaeus vannamei. An experiment was performed with postlarval shrimp (mean initial wet weight 1.2 mg) fed five isoenergic and isonitrogenous diets containing five supplemented levels of chitosan (0, 0.5, 1, 2 and 4 g kg^?1 diet, respectively). The five compound diets (C0, C0.5, C1, C2 and C4) sustained shrimp growth throughout the experiment. Growth performance (final body weights; weight gain; SGR: specific growth rate) in shrimp fed diet C2 was significantly higher than that in shrimp fed diets C0, C0.5 and C1 (P < 0.05), diet C4 treatment provided intermediate growth result. The survival in shrimp fed diet C1 was significantly higher than that in shrimp fed C0 diet (P < 0.05), other diets treatments gave the intermediate survival results. No significant differences were found in growth and survival between diet C2 and C4 treatments. After 9 days of a stress tolerance test, survival in shrimp fed diets C1, C2 and C4 was significantly higher than that in shrimp fed diets C0 and C0.5. We concluded from this experiment that the incorporation of a moderate dietary chitosan was beneficial to the development of postlarval L. vannamei. Considering the effect of chitosan on both growth and survival of postlarval L. vannamei, second‐degree polynomial regression of SGR and survival indicated optimum supplement of dietary chitosan at 2.67 and 2.13 g kg^?1, respectively, so the level of chitosan supplemented in the diet should be between 2.13 and 2.67 g kg^?1.     

Optimal dietary lipid requirement of postlarval white shrimp,Litopenaeus vannamei in relation to growth performance,stress tolerance and immune response

A 25‐day experiment was conducted to evaluate the optimal lipid level for postlarval Litopenaeus vannamei. Shrimp (1.7 mg) were fed five isonitrogenous diets containing grade levels of lipid (96.6, 114.3, 128.5, 136.5 and 154.5 g/kg diet, respectively). Each diet was assigned to four tanks (500 shrimp), and shrimp were fed six times a day. Weight gain was increased with the increasing dietary lipid levels, and the highest weight gain was observed in shrimp fed diet with 154.5 g/kg lipid (p < 0.05). On the contrary, the survival was lowest in shrimp fed the L15.45 and highest in shrimp fed the L11.43. Triglyceride in hepatopancreas was increased, and cholesterol was decreased with the increasing dietary lipid. Pyruvate kinase and AMPK mRNA expression were highest in shrimp fed the L12.85. Malondialdehyde in whole body was positively correlated with the dietary lipid levels. The mRNA expression of SOD and Caspase 3 was highest in shrimp fed the L12.85. After hypoxia stress, shrimp fed the L12.85 showed highest survival. The mRNA expression of superoxide dismutase and Akirin was highest in shrimp fed the L11.43 and L15.45, respectively. Based on the survival after 25‐day feeding trail and after the hypoxia stress, the optimal dietary lipid for postlarval L. vannamei should be 118–124 g/kg.     

Replacement of Fish Meal with Soybean Meal,Alone or in Combination with Distiller's Dried Grains with Solubles in Practical Diets for Pacific White Shrimp,Litopenaeus vannamei,Grown in a Clear‐Water Culture System

The objective of this study was to evaluate inclusion of distiller's dried grains with solubles (DDGS) as partial replacement of commercial, solvent‐extracted soybean meal (SBM) in fish meal‐free diets for Pacific white shrimp, Litopenaeus vannamei. Aquaria connected to a recirculating biofiltration system were utilized to evaluate growth, survival, and feed conversion of shrimp during the 8‐wk feeding trial. Each 110‐L aquarium was stocked with 15 shrimp (mean individual weight 0.99 g) and fed one of five diets: a diet containing 20% fish meal (FM), which served as the control (Diet 1); a diet containing 0% FM and 52.5% SBM (Diet 2); and diets containing 0% FM and either 10, 20, or 30% DDGS as partial replacement of SBM (Diets 3, 4, and 5, respectively). Shrimp were fed according to a pre‐determined feeding chart five times daily (0730, 1030, 1330, 1630, and 1930 h) and there were three replicates per dietary treatment. The results from the feeding trial demonstrated that final weight, weight gain (g), and percentage weight gain were significantly higher (P < 0.05) for shrimp fed Diet 1 (10.96 g, 10.01 g, and 1051%, respectively) compared to shrimp fed diets containing DDGS; however, shrimp fed diets containing DDGS had similar (P > 0.05) final weight, weight gain (g), and percentage weight gain as shrimp fed a diet containing 0% FM and 52.5% SBM (Diet 2). Feed conversion ratio (FCR) of shrimp fed Diet 1 (2.84) was significantly lower (P < 0.05) compared to shrimp fed any other diet. Survival (%) was not different (P > 0.05) among treatments and averaged 77.3% for the study. This study demonstrated that practical shrimp diets containing no FM had an adverse impact on growth performance of white shrimp when grown in a clear‐water system and that further research is needed to refine diet formulations when culturing shrimp in these systems when attempting to feed a diet without FM.     

A Standard Reference Diet for Crustacean Nutrition Research VI. Response of Postlarval Stages of the Caribbean King Crab Mithrax spinosissimus and the Spiny Lobster Panulirus argus

Two experiments were conducted to determine if two proposed crustacean reference diets, BML 81S or HFX CRD-84, could serve as nutritional standards for early postlarval stages of the Caribbean king crab Mithrax spinosissimus or the spiny lobster Panulirus argus . In the first study, after an eight week trial period, survival of postlarval crabs (initial mean weight = 20 mg) was higher ( P < 0.05) for crabs fed a control diet of commercial larval fish feed (66.7%) or BML-81S (45.8%) than for crabs fed HFX CRD-84 (16.7%). Final mean weight was also greater ( P < 0.05) for crabs consuming the fry feed than for crabs fed BML-81S or HFX CRD-84 (710 vs. 460 and 340 mg, respectively). In the second study, after a ten week trial period, survival of second stage postlarval spiny lobsters (initial mean weight = 0.20 g) was greater ( P < 0.05) for animals fed live adult Artemia (93.3%) than for lobsters fed HFX CRD-84 (26.7%) or BML-8lS (0%). Lobsters offered the casein-based BML-81S did not consume the feed and died within 25 days. Results suggest that BML-81S may be an acceptable reference diet for Mithrax spinosissimus , but that neither BML-81S nor HFX CRD-84 is adequate for the early postlarval stages of Panulirus argus .     

Influence of dietary phospholipids level on growth performance,body composition and lipid class of early postlarval Litopenaeus vannamei

One experiment was conducted to determine the nutritive value of phospholipids on growth performance of early postlarval shrimp, Litopenaeus vannamei. Five isoenergic and isonitrogenous diets with five supplemented levels of phospholipids (P1, P2, P3, P4 and P5 with 0, 10, 20, 40 and 80 g kg^?1 diet, respectively) were fed to triplicate groups of L. vannamei (mean initial wet weight 0.8 mg) for 27 days. After the 27‐day feeding trial, the lowest weight gain (WG, %) and specific growth rate (SGR, % day^?1) was found in P1 treatment, the highest WG and SGR was found in P3, P4 and P5 treatments, P2 treatment provided intermediate result and showed significant difference compared to P1, P3, P4 and P5 treatments. Shrimp fed the P1 diet had significantly lower survival than shrimp fed other diets, while no significant difference was found in survival among P2, P3, P4 and P5 treatments. Broken‐line analysis on WG indicated that the optimum dietary phospholipids for early postlarval shrimp, L. vannamei, is 45.96 g kg^?1 diet.     

Evaluation of Distillers Dried Grains with Solubles as an Ingredient in Diets for Pond Culture of the Freshwater Prawn Macrobrachium rosenbergii

Distillers dried grains with solubles (DDGS) were evaluated as an ingredient in practical diets for pond culture of the freshwater prawn Macrobrachium rosenbergii . Juvenile prawns averaging 0.66 ± 0.47 g were stocked into nine 0.02 ha ponds at 19,760/ha. Three isonitrogenous diets (29% crude protein) containing 0, 20, or 40% DDGS were fed to shrimp in triplicate ponds. Average yield, survival, individual weight, and feed conversion did not differ significantly ( P > 0.05) among treatments. When averaged over the three diets, results were: yield, 833 kg/ha; survival, 75%; individual weight, 57 B; and feed conversion, 3.1. It appears that DDGS is a suitable ingredient for use in practical diets for freshwater prawns at levels of up to 40% of the total formulation, when prawns are stocked at the densities used in this study.     

Effects of Artificial Substrate and Stocking Density on the Nursery Production of Pacific White Shrimp Litopenaeus vannamei

Nursery production may be enhanced by the addition of artificial substrate to increase the surface area upon which shrimp graze and to serve as refuge. The objective of this study was to assess the effects of the artificial substrate, AquaMats^TM, on the performance of postlarval Pacific white shrimp Litopenaeus vannamei stocked at three densities. Eighteen 230-L tanks were stocked with 10-d postlarvae (mean weight < 0.01 g). Six treatments were evaluated and consisted of shrimp stocked at three densities (778 shrimp/m², 1,167 shrimp/ m², and 1,556 shrimp/m²) with and without access to artificial substrate. Shrimp in all treatments received a commercial diet ad libitum . After 6 wk, shrimp were harvested from each nursery tank, counted, and batch weighed. Mean final weight, survival, production, feed conversion ratio, and water quality parameters were analyzed by 2-way ANOVA. There were highly significant ( P < 0.001) density and substrate effects on final weight, but there was no significant interaction effect. Final weight was 26.0, 17.4, and 34.5% greater in treatments with substrate than without substrate when stocked at 778, 1,167, and 1,556 shrimp/m², respectively. There was no significant density, substrate, or interaction effect on survival or water quality. Mean survival was ± 89.1% for all treatments. Increased shrimp growth in the presence of added substrate was likely due to the availability of attached particulate organic matter on the AquaMats^TM that served as an additional food source. Results from this study indicate that artificial substrate can be used to mitigate the potential negative effects of high stocking density on growth of L. vannamei in nursery systems.     

Effect of Dietary Astaxanthin on Growth,Survival, and Stress Tolerance of Postlarval Shrimp,Litopenaeus vannamei

The effect of dietary astaxanthin on growth, survival, and stress tolerance was determined in postlarval Litopenaeus vannamei. An experiment was performed with postlarval shrimp (mean initial wet weight 1.2 mg) fed four isoenergic and isonitrogenous diets containing four supplemented levels of astaxanthin (0, 100, 200, and 400 mg/kg diet, respectively). Shrimp fed diets containing 100, 200, and 400 mg astaxanthin/kg diet for 30 d showed higher weight gain (WG, %) and survival compared to the control (without supplementation of astaxanthin). Specific growth rate (SGR, %/day) and final body wet weight (FBW, mg) showed the same pattern as WG. There were no significant differences in growth performance (FBW, WG, and SGR) among the groups fed the diets with astaxanthin supplementation at the termination of feeding trial. Survival of shrimp in the control and 100 mg/kg diet treatments was significantly lower than that of shrimp in the treatments with 200 and 400 mg/kg diet. After 9 d of a stress tolerance test, survival of shrimp in the 200 and 400 mg astaxanthin/kg treatments was significantly higher than that of shrimp in the 0 and 100 mg astaxanthin/kg treatments (P < 0.05). We concluded from this experiment that astaxanthin was a necessary ingredient for the development of larval L. vannamei. Considering the effect of astaxanthin on both, growth performance and survival of postlarval L. vannamei, the level of astaxanthin supplemented in the diet should be between 100 mg and 200 mg/kg of diet.     

Correlation Between Two Size Classes of Pacific White Shrimp Litopenaeus vannamei and Its Potential Implications for Selective Breeding Programs

Abstract.— The correlation between market weight (20–25 g) and broodstock weight (> 35 g) in Pacific white shrimp Litopenaeus vannamei has not been determined. Breeders may assume that the largest brood-stock shrimp were also the largest market shrimp. In this study, 120 market shrimp were individually tagged and grown to broodstock in an earthen pond. There was a significant relationship between market and broodstock weight ( P < 0.001) but it was not highly correlated ( r = 0.42). There was no correlation between market weight and post-market weight gain ( P = 0.477; r = 0.08). Of the largest 20 broodstock, only seven were among the top 20 at market weight. If the goal of a breeding program is to select the fastest growing individuals to market, shrimp should be individually selected at market weight and not as broodstock.     

Management Strategies for Production of the Atlantic White Shrimp Penaeus setiferus as Bait Shrimp in Outdoor Ponds

Abstract The geographic distribution of the Atlantic white shrimp Penaeus setiferus is in coastal waters from New York to Florida and around the Gulf of Mexico. Beside its value to commercial fisheries, this shrimp is sold as bait for recreational fishing. Previous data suggest that demand for live bait shrimp cannot be satisfied by commercial fleets. A 120-d trial was designed to study production of bait size P. setiferus at high densities in eight small outdoor ponds in south Texas. A 2^4–1 fractional factorial design was applied to study the effects of postlarval (PL) density (350 and 700 shrimp/m²), feed type (A and B), and water circulation methods (with and without airlift pumps or center pond dividers) on shrimp growth, survival and yield. No significant differences in survivals or yields were found between treatments (P = 0.2). Feed type ( P = 0.011), airlift pumps ( P = 0.021), and center dividers ( P = 0.026), had significant impacts on shrimp growth rates. Density effect on growth was not statistically significant ( P = 0.055). This study demonstrated that 6-d-old postlarvae can be stocked at 700 per square meter and reached a bait size (6.2 g) in 94 d with a 73.6% survival and a yield equivalent to 31,300 kg/ha when offered a commercial shrimp feed. A preliminary economic analysis based on this data suggests that operating a bait shrimp farm in Texas with two crops/yr will show profitability within 7 to 12 yr with an internal rate of return of 6.5 and 17.6%, respectively.     

Dietary lipid requirement of whiteleg shrimp Litopenaeus vannamei juveniles cultured in biofloc system

An eight‐week feeding trial was conducted to evaluate the contribution of biofloc on dietary lipid requirement in whiteleg shrimp Litopenaeus vannamei. Five diets with graded levels of dietary lipid (45, 60, 90, 120 and 150 g/kg) were fed to juvenile shrimp. Final weight, weight gain and specific growth rate of shrimp fed diets with 60, 90 and 120 g/kg lipid levels were significantly higher than those of shrimp fed diets with lipid levels 45 and 150 g/kg (p < .05). Feed efficiency and protein efficiency ratio of shrimp fed 60, 90 and 120 g/kg were higher than those fed 150 g/kg diet. Plasma total cholesterol and triglyceride levels were lower in shrimp fed 45 g/kg compared with those fed the 90 g/kg (p < .05). Also, lysozyme activity for 90 g/kg group was higher than the 15 g/kg group. Hepatopancreas lipase and amylase activities of shrimp fed 90 and 120 g/kg diets were significantly higher than those of shrimp fed 45 and 150 g/kg diets. Broken‐line regression analysis for weight gain indicated that the dietary lipid requirement of whiteleg shrimp juveniles reared in a biofloc system was estimated to be higher than 56 g/kg but <60 g/kg.     

Prediction of culture performance of juvenile Litopenaeus vannamei by in vitro (pH-stat) degree of feed protein hydrolysis with species-specific enzymes

Rapid in vitro methods for measuring digestibility may be useful in analysing aqua feeds if the extent and limits of their application are clearly defined. The pH‐stat protein digestibility routine with shrimp hepatopancreas enzymes was previously related to apparent protein digestibility with juvenile Litopenaeus vannamei fed diets containing different protein ingredients. The potential of the method to predict culture performance of shrimp fed six commercial feeds (T3, T4, T5, T6, T7 and T8) with 350 g kg^?1 declared crude‐protein content was assessed. The consistency of results obtained using hepatopancreas enzyme extracts from either pond or clear water‐raised shrimp was further verified in terms of reproducibility and possible diet history effects upon in vitro outputs. Shrimps were previously acclimated and then maintained over 56 days (initial mean weight 3.28 g) on each diet in 500‐L tanks at 114 ind m^?2, clear water closed system with continuous renewal and mechanical filtering (50 μm), with four replicates per treatment. Feeds were offered four times daily (six days a week) delivered in trays at feeding rates ranging from 4.0% to 7.0% of stocked shrimp biomass. Feed was accessible to shrimp 4 h daily for 1‐h feeding period after which uneaten feed was recovered. Growth and survival were determined every 14 days from a sample of 16 individuals per tank. Water quality was monitored daily (pH, temperature and salinity) and managed by water back flushing filter cleaning every 7–10 days. Feeds were analysed for crude protein, gross energy, amino acids and pepsin digestibility. In vitro pH‐stat degree of protein hydrolysis (DH%) was determined for each feed using hepatopancreas enzyme extracts from experimental (clear water) or pond‐raised shrimp. Feeds resulted in significant differences in shrimp performance (P < 0.05) as seen by the differences in growth rates (0.56–0.98 g week^?1), final weight and feed conversion ratio (FCR). Shrimp performance and in vitro DH% with pond‐raised shrimp enzymes showed significant correlation (P < 0.05) for yield (R² = 0.72), growth rates (R² = 0.72–0.80) and FCR (R² = ?0.67). Other feed attributes (protein : energy ratio, amino acids, true protein, non‐protein nitrogen contents and in vitro pepsin digestibility) showed none or limited correlation with shrimp culture performance. Additional correlations were found between growth rates and methionine (R² = 0.73), FCR and histidine (R² = ?0.60), and DH% and methionine or methionine+cystine feed contents (R² = 0.67–0.92). pH‐stat assays with shrimp enzymes generated reproducible DH% results with either pond (CV ≤ 6.5%) or clear water (CV ≤ 8.5%) hepatopancreas enzyme sources. Moreover, correlations between shrimp growth rates and feed DH% were significant regardless of the enzyme origin (pond or clear water‐raised shrimp) and showed consistent R² values. Results suggest the feasibility of using standardized hepatopancreas enzyme extracts for in vitro protein digestibility.     

投喂不同饵料对长薄鳅生长的影响

在水温18.6～21.6℃条件下,将初始体质量为(3.91±0.22) g的长薄鳅幼鱼随机分为5组,每组3个重复,每个重复10尾鱼,饲养在圆形玻纤缸(直径1 m、高0.8 m)中,分别投喂刀额新对虾、鳙鱼、配合饲料(粗蛋白≥46.0%)、虾+饲料、鱼+饲料5种饵料,以筛选适宜于长薄鳅幼鱼的适宜饵料投喂模式。75 d的饲养结果表明,不同投喂模式对长薄鳅的存活率无显著性影响(P>0.05),而对长薄鳅的生长影响显著(P<0.05)。试验结果表明,虾组、鱼组、饲料组、鱼+饲料组的长薄鳅最终体质量无显著性差异(P>0.05),但虾+饲料组最终体质量和体质量特定生长率显著高于其他4组(P<0.05),依次为虾+饲料组>饲料组>虾组>鱼组、鱼+饲料组。5个试验组鱼的体长特定生长率无显著性差异(P>0.05),依次为虾+饲料组>虾组>饲料组、鱼+饲料组>鱼组。试验结束时,各试验组鱼的生长离散均有所升高,生长离散变化依次为鱼组>鱼+饲料组>饲料组>虾组>虾+饲料组。各试验组长薄鳅的的摄食率差异显著(P<0.05),摄食率依次为鱼组>虾组>鱼+饲料组>虾+饲料组>饲料组;虾组和鱼组的饵料系数无显著性差异(P>0.05),但显著高于其他3组(P<0.05),其他3组间无显著性差异(P>0.05)。不同投喂模式下长薄鳅幼鱼的生长系数b值均小于3,呈负异速生长,但虾+饲料组的长薄鳅幼鱼生长系数b值最大。试验过程中各组鱼的肥满度均下降。研究结果显示,在本试验的不同饵料投喂模式中,投喂虾+饲料更利于长薄鳅的摄食和生长。     

A Preliminary Evaluation of Naturally Occurring Organisms,Distillery By-Products,and Prepared Diets as Food for Juvenile Freshwater Prawn Macrobrachium rosenbergii

The relative acceptability and suitability of naturally occurring pond organisms identified as likely natural food items for juvenile freshwater prawn, Macrobrachiurn msenbergii, were evaluated under controlled conditions. The potential of direct consumption of materials used as organic pond fertilizer (distillers dried grains with solubles [DDGS] was also evaluated. Growth and survival of prawn fed gastropods, oligochaetes, zooplankton, or DDGS were compared with those fed a nutritionally-complete pellcted diet (control). Groups of five juvenile prawn (average weight 1.66 ± 0.10 g) were stocked into eighteen 7.5-L glass aquaria. Dietary treatments were evaluated in triplicate aquaria for 21 days. Prawn fed live zooplankton exhibited a significantly higher rate of weight gain (P < 0.05) than drawn in other treatments, as measured by differences in slopes of regression lines for weight gain over time. There were no significant differences (P > 0.05) in rates of gain for prawn fed a complete diet and those fed DDGS or gastropods. Prawn fed oligochaetes grew significantly slower (P < 0.05) than those fed the prepared diet. Results indicate that juvenile prawn as large or larger than 2g can utilize live zooplankton and that DDGS may be consumed directly by prawn. Thus, DDGS may serve a dual role as a feed and pond fertilizer. Additional research in pond management strategies that maximize zooplankton and gastropod numbers and the potential of DDGS as a combination food/fertilizer in freshwater prawn production ponds should be conducted.     

Comparison of growth and survival of white shrimp postlarvae (Litopenaeus vannamei) fed dried Artemia biomass versus four commercial feeds and three crustacean meals

The use of dried Artemia biomass meal as an exclusive feed for postlarval white shrimp (Litopenaeus vannamei) was compared with four commercial feeds and three crustacean meals in a series of trials. Postlarvae (PL1–PL6) were stocked at a density of 1.5–2.5/litres in 16 tanks (100 litres volume) and fed, ad libidum, five times a day, over 23–29 days. Feeding postlarval shrimp with dried Artemia biomass resulted in a significantly larger size than feeding with three of the commercial feeds, and the crustacean meals. There was no significant size difference observed in animals fed with Artemia biomass and the commercial 'Golden Pearls' feed for postlarvae, however the coefficient of variation among the size of the 'Golden Pearls' fed animals was significantly higher. The weight increase of animals fed with Artemia biomass was higher than in animals fed with all the tested feeds. The survival rate was not significantly different in animals fed with Artemia flakes from 'Salt Creek', 'Bio-Marine', 'Golden Pearls' and Artemia biomass, however the survival rate was significantly larger in animals fed with Artemia biomass than in animals fed with the crustacean meals and 'Artemac.' Results suggest that dried Artemia biomass is a well-suited feed for postlarval L. vannamei.     

Effects of Dietary Magnesium on Growth and Tissue Magnesium Content of Blue Tilapia Oreochromis aureus

Juvenile blue tilapia Oreochrornis aureus (mean weight 0.5 ± 0.05 g) were stocked into 38 liter glass aquaria receiving Row-through well water containing 0.1 mg magnesium/L and fed semipurified, casein-based diets containing graded levels of magnesium (0.003, 0.008, 0.023, 0.037, 0.050 and 0.065% magnesium, dry weight). Magnesium supplements were provided as anhydrous magnesium sulfate (MgSO₄). No treatment-related mortalities occurred and no visible magnesium deficiency symptoms were observed in any treatment group during the 18 week experimental period. Magnesium concentrations in scale and bone of tilapia fed diets containing 0.023 to 0.065% magnesium were greater ( P < 0.05) than in fish fed diets containing 0.003 to 0.008%. Scale and bone magnesium concentrations did not differ ( P > 0.05) among fish that received dietary magnesium levels of 0.023% or greater. The magnesium content of muscle was higher ( P < 0.05) in fish fed 0.037 to 0.065% magnesium than in those fed 0.003 to 0.008% magnesium. Muscle magnesium concentrations did not differ ( P > 0.05) among fish that received 0.037% or more dietary magnesium. Adequate weight gain and superior feed efficiency occurred in fish fed 0.05 to 0.065% magnesium. Results indicated that diets for O. aureus should contain at least 0.05% magnesium (500 mg Mg/kg dry diet) for optimum growth and normal tissue mineralization.     

Efficacy of silicone-coated ascorbic acid and ascorbyl-2-polyphosphate to fast-growing tiger shrimp (Penaeus monodon)

Growth, survival, tissue ascorbate concentration and collagen content were studied in fast-growing Penaeus monodon fed two ascorbic acid (AA) derivatives. Prior to the experimental trial, shrimp (initial body weight: 0.9 ± 0.4 g) were fed on a diet lacking vitamin C for 5 weeks. During the following 13-week experiment, the shrimp (initial body weight: 8.2 ± 0.7 g) were given one of five squid-meal-based diets. The dietary treatments consisted of a diet lacking vitamin C, two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of silicone-coated AA, and two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of ascorbyl-2-polyphosphate. Shrimp gained 18.3 g in 13 weeks. The AA-free diet group exhibited the lowest growth rate, feed intake and survival (26.8%) after 4 weeks. Hepatopancreatic ascorbate and muscle collagen content were significantly ( P < 0.05) lower in AA-deprived shrimp. At the end of the feeding trial, growth rate and survival were not significantly ( P > 0.05) different among groups fed AA-supplemented diets. Hepatopancreatic and haemolymphatic ascorbate concentrations were significantly ( P < 0.05) higher in groups given ascorbyl-2-polyphosphate than in groups given silicone-coated AA. A supplement of 500 mg AA kg⁻¹ diet in the form of either silicone-coated AA or ascorbyl-2-polyphosphate was adequate for optimal growth. But ascorbate concentrations in tissues remained much below saturation levels with a supplement of 1000 mg AA kg⁻¹ diet. It is questionable whether the established vitamin C requirements for P. monodon are adequate to maintain tissue ascorbate in fast-growing juveniles.     

Effect of feeding frequency and feeding time on growth of Penaeus vannamei (Boone)

Abstract. An intensive growth trial conducted In pens in an earthen pond indicated that growth of Penaeus vannamei (Boone) increased with feeding frequency and suggested that day feedings produce greater growth than night feedings. The differences in growth due to feeding frequency were significant, instantaneous growth rates (IGR) increasing from 1·62% to 1·66% to 1·71%/day as the number of feedings increased from one to two to four per 24 h. Comparison of the IGR of shrimp fed at night (1·64%/day) to that of shrimp fed during the day (1·68%/day) suggested ( P = 0·0633) that growth was greater for shrimp given day feedings than for shrimp given night feedings. Survival of shrimp was not significantly different due to feeding frequency or due to time of feeding and averaged 74·7 ± 6·1%. Results indicate that P. vannamei cultured under conditions similar to those tested should be fed a minimum of four times daily and suggest that feeding during the day is at least as good as and may be preferable to feeding at night.