Effects of dietary n‐3HUFA on juvenile white shrimp,Litopenaeus vannamei: Growth,feed utilization,antioxidant enzymes activities and fatty acid compositions

Present study investigates the effects of n‐3 high‐unsaturated fatty acid (n‐3HUFA) levels on growth performance, antioxidant enzymes activities and fatty acid compositions of juvenile Litopenaeus vannamei. These represented seven iso‐nitrogenous and iso‐lipidic diets. Analysed n‐3HUFA concentrations were 0.16% (control), 0.48%, 0.74%, 1.39%, 2.39%, 2.92% and 3.44% respectively. A total of 840 juvenile L. vannamei were randomly stocked into 21 0.5 m³ tanks for 56 days. A significant increase (p < 0.05) was observed from 0.16% to 0.74% n‐3HUFA and a decrease when n‐3HUFA was above these levels in weight gain rate (WGR) and specific growth rate. Total cholesterol, triglyceride and low‐density lipoprotein in serum showed a significant decrease, high‐density lipoprotein showed a significant increase (p < 0.05). Phenoloxidase activity in serum and sodium‐potassium adenosine triphosphatase activity in gill were significantly affected by dietary n‐3HUFA (p < 0.05), both of them showing a downward trend after upward. Malic dehydrogenase and superoxide dismutase activities in serum were also significantly affected by dietary n‐3HUFA (p < 0.05), which rose first and then decreased in general, both of them have a maximum in 2.39% group. No significant differences of the activities of aspartate transaminase and alanine transaminase were observed among all groups (p > 0.05). With dietary n‐3HUFA increase, both ∑HUFA and n‐3HUFA contents gradually increased in hepatopancreas and tail muscles (p < 0.05). Based on broken‐line regression analysis of WGR, the optimal n‐3HUFA requirement is 0.89% for juvenile L. vannamei with initial weight of 0.50 ± 0.01 g.     

饲料蛋白质水平与投喂频率对吉富罗非鱼幼鱼生长及部分生理生化指标的影响

为探讨饲料蛋白质水平与投喂频率对罗非鱼生长及生理健康的影响,采用2×3双因子实验,研究饲料蛋白质水平(36.27%和26.02%)与投喂频率(1、2和3次/d)对吉富罗非鱼幼鱼生长、体成分、血清指标和肝胰脏结构的影响。养殖周期为42 d,结果表明:随饲料蛋白质水平的增加,实验鱼的末体质量(FW)、增重率(WGR)、特定生长率(SGR)、饲料效率(FE)、肥满度(CF)、去内脏全鱼灰分(EWA)、内脏水分(VM)、高密度脂蛋白胆固醇(HDLC)水平显著升高(P0.05),而摄食率(FI)、脏体比(VSI)、饲料成本(FC)、去内脏全鱼粗脂肪(EWF)、内脏粗脂肪(VF)、肝胰脏粗脂肪(HF)显著降低(P0.05);随投喂频率的增加,实验鱼的FW、WGR、SGR、肝体比(HSI)、CF、FC、EWF、VF、HF,血清中的总胆固醇水平(TCHO)、HDLC、低密度脂蛋白胆固醇(LDLC)、总蛋白(TP)、甘油三酯(TGK)水平显著升高(P0.05),而FE、蛋白质效率(PER)、去内脏全鱼水分(EWM)、EWA、VM、肝胰脏水分(HM)显著降低(P0.05)。饲料蛋白质水平和投喂频率对实验鱼的FW、WGR、SGR、VM和HDLC的交互作用显著(P0.05)。投喂26.02%蛋白质水平饲料的实验鱼,肝胰脏细胞肿大变形,呈现透明的空泡化,出现细胞核偏移;而投喂36.27%蛋白质饲料的实验鱼,大多数肝细胞胞浆清晰,可观察到的肝细胞空泡面积较小。综合考虑,饲料蛋白质含量为36.27%是适合吉富罗非鱼幼鱼的,其适宜的投喂频率为2次/d以上,可根据罗非鱼市场情况进行调节。     

Effect of dietary substitution of sea tangle (ST), Laminaria japonica with rice bran (RB) on growth and body composition of juvenile abalone (Haliotis discus)

Dietary substitution effect of sea tangle (ST) with rice bran (RB) on growth and carcass composition of juvenile abalone (Haliotis discus) was determined. Juvenile abalone was acclimated to the experimental conditions for 4 weeks. Seventy juvenile abalone averaging 0.43 g were randomly distributed into each of the 18, 70 L plastic rectangular containers. The experimental diets were fed to abalone once a day at a satiation level with a little leftover. The feeding trial lasted for 16 weeks. Survival of abalone was not affected by dietary substitution of ST with RB. However, weight gain of abalone fed the RB40 diet was higher than that of abalone fed the all other diets except for the RB0 diet. No significant difference in weight gain was found in abalone fed between the RB0 and RB100 diets. SGR of abalone fed the RB40 diet was higher than that of abalone fed the all other diets. Also SGR of abalone fed the RB0 diet was higher than that of abalone fed the RB100 diet, but not different from that of abalone fed the RB20, RB60 and RB80 diets. Moisture, crude protein and ash content of the soft body of abalone were affected by dietary substitution of ST with RB. In conclusion, the 100% ST could be substituted with RB without a retardation of weight gain of abalone when the 20% ST was included into the experimental diet. However, the best growth performance was obtained in abalone fed the RB40 diet substituting 40% ST with RB.     

Influence of 18:2n‐6/20:5n‐3 ratio in diets on growth and fatty acid composition of juvenile abalone,Haliotis discus hannai Ino

A 120‐day feeding trial was conducted to examine the effects of the ratio of dietary linoleic acid (LA, 18:2n‐6) to eicosapentaenoic acid (EPA, 20:5n‐3) on the growth and fatty acid composition of juvenile Haliotis discus hannai (initial shell length 10.23 ± 1.48 mm; initial body weight 0.13 ± 0.05 g) in a recirculation water system. Five semipurified diets with 35 g kg^?1 total lipid were formulated to contain graded LA/EPA ratios (1 : 0, 0.75 : 0.25, 0.5 : 0.5, 0.25 : 0.75, and 0 : 1, respectively). Twenty‐five juveniles were stocked in a rearing unit, a plastic basket (20 × 20 × 10 cm), as a replicate, and there were three replicates for each dietary treatment. The results showed that abalone survival rates were generally high (90.1–98.3%) and independent of the dietary treatments. However, abalone growth was significantly affected by LA/EPA ratio (P < 0.05). The LA/EPA ratio of 0.25 : 0.75 (Diet 4) produced the highest weight gain rate (WGR, 416.3%), closely followed by the ratio of 0 : 1 (Diet 5, 412.9%), the ratio of 0.5 : 0.5 (Diet 3, 399.7%) and the ratio of 0.75 : 0.25 (Diet 2, 372.1%), but no significant differences were observed among these treatments. The abalone fed the diet without 20:5n‐3 (Diet 1) had the lowest WGR (Diet 1, 363.8%), which was significantly lower than that of Diet 4. Fatty acid profiles in abalone body reflected those of dietary lipids, especially for the polyunsaturated fatty acids. The contents of arachidonic acid (AA; 20:4n‐6) in abalone tissues were positively correlated with dietary level of 18:2n‐6 (P < 0.05). Similar correlation was also observed between the level of docosahexaenoic acid (DHA, 22:6n‐3) in abalone tissues and the level of dietary EPA. It is suggested that abalone, H. discus hannai, have the capacity to synthesize 20:4n‐6 from 18:2n‐6, and maybe 22:6n‐3 from 20:5n‐3.     

仿刺参幼参对亮氨酸最适需求量的研究

为探究仿刺参幼参对亮氨酸的最适需求量,在基础饲料中分别添加0.00%、0.80%、1.60%、2.40%、3.20%和4.00%的包膜亮氨酸,配成亮氨酸含量分别为1.29%(D1,对照组)、1.63%(D2)、1.98%(D3)、2.22%(D4)、2.58%(D5)和2.97%(D6)的6组实验饲料,饲喂初始体质量为(16.40±0.14) g的仿刺参幼参60 d。结果显示,(1)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参幼参的增重率和特定生长率显著升高,在D3组增重率达到最大值100.84%,随亮氨酸含量进一步提高,增重率和特定生长率显著降低,但D3、D4和D5组增重率和特定生长率还是显著高于对照组;(2)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参体壁的粗脂肪含量显著升高,在D3组达到最大值5.50%,且显著高于其他组,随亮氨酸含量进一步提高,仿刺参体壁粗脂肪含量显著降低,各组间水分、粗蛋白质和粗灰分含量均无显著性差异;随饲料亮氨酸含量的升高,仿刺参体壁蛋氨酸含量显著提高;(3)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参肠道脂肪酶和蛋白酶活性显著提高,...     

鲈幼鱼对饲料中苏氨酸的需要量

以初始体质量(8.00±0.20)g的鲈为实验对象,在海水网箱(1.5 m×1.5 m×2.0 m)中进行为期8周的摄食生长实验,研究鲈对饲料中苏氨酸的需要量。通过在半精制基础饲料中添加晶体L-苏氨酸使饲料中苏氨酸含量分别达到0.75%、1.03%、1.36%、1.67%、2.04%和2.31%,配制成6水平等氮等能饲料(41.83%粗蛋白质,19.68 kJ/g总能)。每种饲料设3个重复,每个重复随机放养30尾鲈。实验采用表观饱食投喂方式,每天投喂2次(06:00和17:30),实验期间水温为26～32℃,盐度为22～28,溶解氧含量在7 mg/L左右。实验结果表明,各饲料处理组成活率(94.4%～98.9%)无显著差异。随着饲料中苏氨酸含量的增加,鲈的增重率显著升高(150.3%～256.9%)(P<0.05),且在1.67%苏氨酸饲料组达到最大值(256.9%),然而,随着饲料中苏氨酸含量的进一步增加,增重率有下降的趋势。鲈的氮累积率随着饲料中苏氨酸含量的增加而显著升高(13.18%～26.36%)(P<0.05),且在1.67%苏氨酸饲料组达到最大值(26.36%),随着饲料中苏氨酸含量的进一步增加,氮累积率有下降的趋势。饲料苏氨酸含量对鲈鱼体粗蛋白、粗脂肪和灰分含量无显著影响。以增重率和氮累积率为评价指标经二次回归分析得出,鲈对饲料中苏氨酸的需要量分别为1.77%和1.88%,占饲料蛋白质的4.21%和4.47%。     

Effects of dietary α‐lipoic acid on the growth and antioxidative responses of juvenile abalone Haliotis discus hannai Ino

A feeding experiment was conducted to determine the effects of α‐lipoic acid (LA) on the growth and antioxidative responses of juvenile abalone Haliotis discus hannai Ino. Six purified diets supplemented with 0, 200, 400, 800, 1600 and 3200 mg kg^?1 of LA, respectively, were fed to abalone for 16 weeks in a flow‐through water system. The results showed that the weight gain ratio (WGR) increased with the dietary LA levels, and reached the highest value in the group with 800 mg kg^?1 dietary LA supplement. Glutathione peroxidase activity in the 800 mg kg^?1 dietary LA group was significantly higher than that in the dietary LA‐deficient (0 mg kg^?1) group. Superoxide dismutase activities in the 200, 400 and 800 mg kg^?1 groups were significantly increased. Supplements of 200, 400 and 800 mg kg^?1 dietary LA elevated the total antioxidative capacity significantly. The glutathione level in the hepatopancreas increased significantly with the dietary LA supplements in a dose‐dependent manner (except for the 200 mg kg^?1 group). Catalase and malondialdehyde in the hepatopancreas were not significantly affected by dietary LA. In conclusion, dietary LA promoted the growth and stimulated the antioxidative defence capacity of abalone. Based on the data of WGR, the optimal dietary LA supplement for juvenile abalone was found to be 709 mg kg^?1 using piece‐wise linear analysis.     

Dietary histidine requirement of juvenile blunt snout bream (Megalobrama amblycephala)

An eight‐week feeding trial was conducted to determine the dietary histidine requirement of juvenile blunt snout bream. The results showed that final body weight, weight gain rate and specific growth rate significantly increased with increasing dietary histidine levels up to 9.9 g/kg (p < .05) and decreased gradually thereafter, while feed conversion ratio showed a converse trend. The survival rate, condition factor, viscerosomatic and hepatosomatic index were not significantly affected by the graded dietary histidine levels (p > .05). About 9.9 g/kg dietary histidine level significantly improved whole‐body protein and lowered moisture content. The contents of plasma total protein, cholesterol, urea and triglyceride levels were not significantly affected by dietary histidine levels. About 9.9 g/kg dietary histidine level significantly upregulated target of rapamycin and insulin‐like growth factor mRNA levels (p < .05), and 12.1 g/kg and 14.2 g/kg dietary histidine levels significantly upregulated eukaryotic translation initiation factor 4E‐binding protein 2 and ribosomal protein S6 kinase‐polypeptide 1 mRNA levels (p < .05). Based on second‐degree polynomial regression analysis of weight gain rate, and specific growth rate against dietary histidine levels, the dietary histidine requirement for juvenile blunt snout bream was estimated to be 11.2 g/kg of diet, corresponding to 36.1 g/kg of dietary protein.     

Dietary methionine affects growth and the expression of key genes involved in hepatic lipogenesis and glucose metabolism in cobia (Rachycentron canadum)

Juvenile cobia (Rachycentron canadum), a carnivorous fish, was chosen to examine the effects of methionine (Met) supplementation of low fishmeal diets on growth and the expression of key genes related to hepatic lipogenesis and glucose metabolism. Seven isonitrogenous and isolipidic diets were formulated to contain 7.2, 9.0, 10.0, 12.4, 14.1, 16.3 and 18.6 g/kg dietary Met levels. Healthy cobia (initial average weight ± SE = 9.79 ± 0.04 g) were randomly assigned into seven groups in triplicate with 40 individuals per sea cage for 8 weeks. The results showed that the weight gain rate (WGR) of fish increased as the dietary Met was increased up to 12.4 g/kg and then decreased. The expression of insulin‐like growth factor‐I (IGF‐I) and target of rapamycin (TOR) genes was inhibited by the Met‐deficient diets. The mRNA levels of fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP1) genes increased with increasing dietary Met until 12.4 g/kg after which the former remained constant, whereas the latter decreased from 12.4 to 18.6 g/kg Met. The mRNA levels of pyruvate kinase (PK) increased as the dietary Met levels increased, reaching a peak at 12.4 g/kg, and then decreased with further increases in Met. However, the mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) decreased as the dietary Met was increased up to 12.4 g/kg and then remained constant from 12.4 to 18.6 g/kg Met. In conclusion, based on the straight broken‐line analysis of WGR against dietary Met levels, the optimal dietary Met requirement for juvenile cobia was estimated to be 12.4 g/kg (26.9 g/kg dietary protein). A diet with the optimal level of Met induces fish growth and is associated with increased IGF‐I and TOR.     

Dietary lysine requirement of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to determine dietary lysine requirement of juvenile Pseudobagrus ussuriensis (initial body weight: 0.60 g). Six isonitrogenous (crude protein, 400 g/kg) and isolipidic (crude lipid, 50 g/kg) diets were formulated to contain graded levels of dietary lysine (12.8, 19.9, 26.5, 34.0, 40.8 and 44.1 g/kg dry diets, respectively). The results indicated that weight gain, specific growth rate, productive protein value and protein efficiency ratio increased, while feed conversion ratio decreased with increasing dietary lysine level up to 34.0 g/kg dry diet and then levelled off. Fish fed diet with 12.8 g/kg lysine had the lowest lysine content (58.6 g/kg dry matter) in muscle, while fish fed diet with 34.0 g/kg lysine had the highest value (61.6 g/kg dry matter; p < .05). Broken‐line analysis on the basis of weight gain showed that the optimal dietary lysine requirement for maximum growth of juvenile Pseudobagras ussuriensis is 33.5 g/kg dry diet (82.4 g/kg dietary protein). Quadratic regression analysis of protein efficiency ratio against dietary lysine levels indicated that the optimal dietary lysine requirement of juvenile Pseudobagras ussuriensis is 36.4 g/kg dry diet (89.5 g/kg dietary protein).     

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.     

A comparative study on protein‐sparing effects among juvenile Erythroculter ilishaeformis line,Ancherythroculter nigrocauda line and their hybrid F1 fed diets with different protein to carbohydrate ratios

To investigate the mechanism underlying the difference of dietary protein requirements among Erythroculter ilishaeformis line, Ancherythroculter nigrocauda line and their hybrid F₁ (E. ilishaeformis♀×A. nigrocauda ♂), juvenile fish of these three species with initial body weight (5.86 ± 0.10 g) were fed the six isoenergy diets with different dietary protein/carbohydrate ratios (P/C ratios were 0.56, 0.78, 1.11, 1.61, 2.52 and 4.43, respectively) for 8 weeks. The results showed that the hybrid culter had the higher weight gain rate (WGR), protein efficiency ratio and protein deposition ratio compared with its parents lines; using WGR as a response criteria, the dietary carbohydrate tolerant level of juvenile E. ilishaeformis line, A. nigrocauda line and their hybrid was 24.3%, 28.5% and 29.7%, respectively, and the optimal P/C ratio was 1.69, 1.35, 1.22 and respectively. Dietary carbohydrate activated hepatic protein kinase B (Akt), dietary protein activated hepatic target of rapamycin (TOR) and the induction of mRNA expression of hepatic phosphoenolpyruvate carboxykinase and pyruvate kinase showed a similar change in hybrid F₁ and its parents. A. nigrocauda had the highest enzymes activities in intestinal protease and amylase, and hybrid culter had the highest intestinal lipase activities. Our results demonstrated that the hybrid culter has the better protein‐sparing effects by increasing carbohydrate metabolism than its parent lines.     

Grow-out culture of tropical abalone, Haliotis asinina (Linnaeus) in suspended mesh cages with different shelter surface areas

Thisstudy investigated the effects of shelter surface area (SSA) on the feeding,growth and survival of the donkey-ear abalone, Haliotisasinina reared in mesh cages (0.38×0.38×0.28m) suspended in flow-through tanks (water volume = 6m³). Cages had sections of polyvinylchloride (PVC) thatprovided shelters with surface area of 0.22 m², 0.44m² and 0.66 m².Hatchery-produced abalone with initial shell length of 32 ± 1mm and wet weight of 7.5 g were stocked at 50individuals cage^–1 that corresponded to stocking densities ofca. 227, 113 and 75 abalone m^–2 of SSA. The ratios of sheltersurface area to cage volume (SSA:CV) were 5.5, 11 and 16.5. Abalones wereprovided an excess red seaweed Gracilariopsis bailinae(= Gracilaria heteroclada) at weekly intervals overa 270-day culture period. Feeding rates (18–20% of wet weight), foodconversion ratio (26–27) and percent survival (88–92%) did notdiffer significantly among treatments (p > 0.05). Body size at harvest rangedfrom 56 to 59 mm SL and 52 to 57 g wet body weightwith significant differences between abalone reared at SSA 0.22m² and 0.66 m² (p < 0.05).Abalone reared in cages with 0.66 m² SSA grewsignificantly faster at average daily growth rates of 132 m and188 mg day^–1. Stocking densities of 75–113m^–2 SSA in mesh cages suspended in flow-throughtanks resulted in better growth of abalone fed red seaweed.     

The growth of disk abalone, Haliotis discus hannai at different culture densities in a pilot-scale recirculating aquaculture system with a baffled culture tank

The growth rate of disk abalone, Haliotis discus hannai, energy consumption and changes in water quality were monitored in a pilot-scale recirculating aquaculture system (RAS) for 155 days. Baffles were installed in the RAS culture tanks to enlarge the attachment area and clean out solid waste materials automatically by hydraulic force only. The experimental disk abalones, of shell length 24.5 ± 0.5 mm, were cultured at three stocking densities, 700, 1300 and 1910 individuals/m² bottom area, in triplicate. The abalones were fed with sea mustard, Undaria pinnatifida, once a week. The abalone feed conversion rates and daily growth rates ranged from 24.5 to 25.9 and 0.32 to 0.36%, respectively. Their daily shell increments and survival rates ranged from 67.7 to 78.6 μm/day and 87.6–92.2%, respectively. The growth in weight tended to decrease at a culture density of 1300 individuals/m² bottom area, while shell increments and survival rates were acceptable at this density. The total power consumption for heating was 1185.4 kW, comprising 30.2% of the total power consumption, while the average water exchange rate was only 2.9% per day. The total ammonia nitrogen stabilized below 0.07 mg/L, after conditioning of the biofilter. The NO₂⁻–N, NO₃⁻–N and total suspended solid concentrations were also maintained within acceptable ranges for the normal growth of disk abalone. The use of the RAS with these newly designed culture tanks for disk abalone culture produced 1300 individuals/m² bottom area with a water exchange rate of only 2.9% per day and used about one-tenth of the heat energy of a conventional flow-through system.     

Dietary value of gametophytes and juvenile sporophytes of the brown macroalga <Emphasis Type="Italic">Eisenia bicyclis</Emphasis> for juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis>

The dietary value of juvenile stages (gametophyte and juvenile sporophyte) of the brown macroalga Eisenia bicyclis for post-larval and juvenile abalone Haliotis diversicolor of 2.0–6.5 mm in shell length (SL) was examined and compared with that of a benthic diatom, Nitzschia sp., in laboratory experiments. Most abalone actively fed on these diets, but there were large variations in the growth rate among the diets and among the growth stages of abalone. Growth rates of abalone fed on Nitzschia sp. were highly variable within each growth stage, but showed no clear differences among growth stages. In contrast, in abalone fed gametophytes or juvenile sporophytes, growth rates linearly increased as abalone grew. Growth rates of >60 μm SL/day were observed in juveniles of >3 mm SL fed gametophytes, and juveniles of >5 mm SL fed juvenile sporophytes. These results indicate that the dietary value of the juvenile stages of E. bicyclis for the abalone changes as they grow, and with growth juvenile abalone begin to efficiently utilize gametophytes and juvenile sporophytes in that order.     

Dietary calcium requirement of red swamp crayfish (Procambarus clarkia)

To investigate dietary calcium requirement of red swamp crayfish (Procambarus clarkia), six semi‐purified diets were formulated to contain different concentrations of calcium (2.7(control group), 6.1, 11.9, 17.6, 23.5 and 29.1 g/kg calcium). Each diet was hand‐fed to triplicate of 15 crayfish with average initial body weight (6.22 ± 0.87) g for 8 weeks. The results showed that weight gain rate (WGR) significantly increased and feed conversion ratio (FCR) significantly decreased from 11.9 to 23.5 g/kg groups (p < .05). Protease activities in intestine and hepatopancreas and parathyroid hormone concentrations in serum significantly decreased with increasing dietary calcium levels (p < .05), while calcium and phosphorus contents in exoskeleton, calcium content in muscle and calcitonin concentrations in serum significantly increased (p < .05). The activities of lipase and amylase in intestine and hepatopancreas, serum alkaline phosphatase and total vitamin D concentrations in serum had significant increase as dietary calcium content increased up to 11.9–17.6 g/kg (p < .05). The inorganic phosphorus content in 29.1 g/kg group was significantly lower than those in other groups (p < .05). Broken‐line model analysis based on WGR and quadratic curve model analysis based on FCR showed that optimal dietary calcium requirement of red swamp crayfish ranged from 12.7 to 17.1 g/kg.     

Cholesterol requirement and phytosterols efficiency in semi‐purified diets of juvenile Pacific white shrimp Litopenaeus vannamei

Studies pertaining to cholesterol requirement are limited based on the levels evaluated and statistical analysis. Two trials were conducted to refine cholesterol requirement in Pacific white shrimp Litopenaeus vannamei feeds. The basal diet was supplemented with graded levels of cholesterol (ranging from 0.48 to 1.85 g/kg) in trial 1. Since the shrimp (initial weight: 0.24 g) growth response was very linear without reaching a plateau, it was not clear whether the requirement was met. Hence, a second trial was designed using eight diets designed with an increased range of cholesterol levels from 0.45 to 4.57 g/kg of diets. The shrimp (0.38 g initial weight) reached a final weight of (4.31–7.43 g) or per cent weight gain from 1,014%–1,874% (n = 4) after 6 weeks. Saturation kinetic model and broken‐line models with linear or quadratic ascending portions were used to evaluate dose–response relationships of feed efficiency (FE), thermal‐unit growth coefficient (TGC), whole‐body cholesterol (CHOL) and cholesterol deposition (CHOLD) against dietary cholesterol. The cholesterol requirement of shrimp was estimated at 1.9 (1.1–4.3) g/kg, 1.7 (1.1–3.4) g/kg, 2.5 (2.3–2.9) g/kg and 2.7 (2.4–3.1) g/kg of shrimp diet for FE, TGC, CHOL and CHOLD, respectively. Additionally, based on improved growth, the inclusion of phytosterol can serve as a partial replacement for cholesterol.     

饲料糖脂比对吉富罗非鱼生长、血液指标和肝脏糖代谢关键酶活性及基因表达的影响

为探讨糖脂比对吉富罗非鱼幼鱼生长性能、血液生化指标和肝脏糖代谢关键酶的影响,本实验设计了5种不同糖脂比(1.5、2.3、3.9、7.0、16.5)的等氮等能饲料,以吉富罗非鱼幼鱼为实验对象,进行了为期8周的饲养实验。结果显示,随饲料中糖脂比升高,吉富罗非鱼特定生长率(SGR)、增重率(WGR)和蛋白质效率(PER)先升高后降低,糖脂比为3.9和7.0时,WGR、SGR和PER最高。饵料系数(FCR)的变化趋势与此相反,在糖脂比为3.9和7.0组显著低于其他组。随着饲料糖脂比的增加,吉富罗非鱼全鱼粗脂肪含量逐渐下降,在糖脂比为16.5时达到最低水平,但仅与1.5组存在显著差异。血浆甘油三酯在糖脂比最高组也出现显著降低,血浆胆固醇同样在糖脂比最高组显著低于3.9组。然而血糖的变化趋势相反,当糖脂比为16.5时显著高于其他组。随着糖脂比的升高,吉富罗非鱼幼鱼肝脏中丙酮酸激酶(PK)的活性及mRNA表达量逐渐升高,而磷酸烯醇式丙酮酸羧激酶(PEPCK)的活性及mRNA表达水平则逐渐下降。根据二次回归模型得出,在等氮等能的饲料条件下,吉富罗非鱼幼鱼最适宜的糖水平和脂肪水平分别为49.69%和9.53%,其对应的糖脂比为8.4。     

Dietary manganese requirement of juvenile hybrid grouper,Epinephelus lanceolatus × E. fuscoguttatus

An 8‐week feeding trial was conducted to estimate the optimum dietary manganese (Mn) requirement for juvenile hybrid grouper, Epinephelus lanceolatus × E. fuscoguttatus. The basal diet was formulated to contain 520 g/kg crude protein from casein and fishmeal. Manganese methionine was added to the basal diet at 0 (control group), 2.5, 5, 10, 20 and 40 mg Mn/kg diet providing 7.48, 10.34, 13.76, 19.72, 31.00 and 53.91 mg Mn/kg diet, respectively. Each diet was randomly fed to triplicate groups of juveniles, and each tank was stocked with 20 fish (initial weight, 60.06 ± 0.68 g). The manganese content in rearing water was monitored and kept below 0.01 mg/L. Results showed that the weight gain ratio (WGR), protein efficiency ratio (PER), specific growth rate (SGR), Mn contents in whole body, liver and vertebra, and activities of hepatic Mn superoxide dismutase (Mn‐SOD), total SOD (T‐SOD) and glutathione peroxidase (GSH‐PX) were significantly improved by dietary Mn supplementation (p < .05). However, dietary Mn did not affect arginase (DArg) activity. The highest feed conversion ratio (FCR) was observed in fish fed the basal diet (p < .05). No significant differences were found on the Cu and Zn contents in whole body by supplementing dietary Mn. Supplemented Mn in diets had significantly effect on liver and vertebral trace element deposition (p < .05). Fish fed the basal diet had the highest Fe and Zn contents in vertebra (p < .05). There were no significant differences on hepatic pyruvate decarboxylase (PDC) activity with supplemented Mn levels below 13.76 mg/kg. As biomarker of oxidative stress, malondialdehyde (MDA) content in liver was significantly higher in fish fed the basal diet (p < .05). Using the broken‐line models based on SGR, dietary Mn requirement of the juvenile hybrid grouper was estimated to be 12.70 mg/kg diet.     

脱脂亮斑扁角水虻幼虫粉替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响

为研究脱脂亮斑扁角水虻幼虫粉(DBSFLM)替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响,本实验选用平均体质量为(1.67±0.01) g的黄颡鱼幼鱼480尾,随机分为4个处理组,分别投喂基础饲料(T0)和实验饲料[脱脂亮斑扁角水虻幼虫粉分别替代鱼粉20%(T20)、40%(T40)和60%(T60)],每个处理组3个重复,每个重复40尾鱼,养殖8周。结果显示,随着DBSFLM替代量的增加,黄颡鱼生长呈先增加后降低的趋势;T20组的终末均重、增重率和特定生长率最高,且显著高于T60组;实验组T20和T60的摄食量显著高于对照组和T40组;实验组的腹脂指数、灰分和钙沉积率呈下降趋势,其中T60组的腹脂指数、T40和T60组的灰分和钙沉积率达到显著水平;与对照组T0相比,实验组的肥满度、脏体比、肝体比、肠体比和胃体比、蛋白质、脂肪和磷沉积率及黄颡鱼体蛋白、体脂肪和灰分均没有显著差异;血清胆固醇和甘油三脂显著降低,高密度/低密度脂蛋白胆固醇显著升高,实验组T40的胃蛋白酶活性有增加趋势、肠道胰蛋白酶活性显著增加。研究表明,在本实验条件下,脱脂亮斑扁角水虻幼虫粉替代鱼粉不影响黄颡鱼幼鱼的生长性能和体组成含量,并可降低腹脂指数、血清甘油三酯、胆固醇含量及灰分、钙的沉积率,还可增加蛋白酶活性,以20%替代比例生长最佳,且优于对照组。