饲料Vc对异育银鲫的生理效应及其适宜添加量

在精制饲料中分别添加不同剂量Vc(0、37.5、75、15 0、30 0、6 0 0和 12 0 0mg/kg) ,连续投喂异育银鲫 (方正银鲫♀×兴国红鲤♂ ) (Carassiusauratusgitelio) 8周。结果显示 ,当饲料中缺乏Vc时异育银鲫虽没有出现明显的缺乏症状 ,但日增重率、血红蛋白含量和血清POD酶活性均低于Vc添加组 ,而红细胞脆性极显著地高于高剂量Vc添加组 (P <0 .0 1) ;同时 ,经新复极差检验 ,在适宜范围内随着饲料Vc含量增加 ,异育银鲫日增重率、血红蛋白含量、POD活性等指标显著提高 ,而红细胞脆性明显下降 (P <0 .0 5 )。综合以上指标的非线性回归分析结果 ,建议生产上异育银鲫饲料Vc适宜添加量为 30 0～ 5 0 0mg/kg。     

Dietary essentiality of ascorbic acid in rohu larvae: Quantification with ascorbic acid enriched zooplankton

Carp larvae, like any other fish larvae dependon natural food during first few days of theirlife. In nursery conditions, high mortality andslow larval growth are of common occurrence;sub-optimal nutrition might be a possiblereason for such consequences. To improve thesituation the effect of feeding ascorbicacid-enriched live food on survival, growth,tissue biochemical composition includingascorbate level was evaluated in first feeding(3 days old) larvae (av. wt. 2.2 mg) of therohu carp, Labeo rohita (Ham.) for aperiod of 15 days (temp. 28.6 ± 1 °C)under natural photoperiod. The larvae (stockingdensity 10 l^–1) were offered enriched andnon-enriched zooplankton ad libitumfollowing a rigid schedule with four feedingregimes, each having 3 replicates. In treatmentT₁, non-enriched zooplankton (Moina,Daphnia, Cyclops, Diaptomus) and in T₂,T₃, T₄ ascorbic acid enriched (12 henrichment) zooplankton [@10%, 20% and 30%ascorbyl palmitate (AP) inclusion in diet ofzooplankton] were offered. Highest survival(90%) and growth (9563% live weight gain)could be seen in T₃ group and the lowestin T₁ (62% survival and 805% live weightgain), thus confirming the dietary essentialityof ascorbic acid for rohu larvae. Therequirement has been shown to be 1409 µg/gdry diet. Whole body tissue analyses for crudeprotein, total lipid and RNA: DNA ratiofollowed the same trend as that of growthresponse and percent survival. Significantpositive correlation (r = 0.949 and 0.861) couldbe found with muscle RNA/DNA ratio and muscleRNA content with specific growth rate indifferent treatments. Significant differencewas found in tissue ascorbate levels betweenenriched plankton fed groups, being highest in T₃. Such live foodmediated vitamin transfer might be an effectivemeans to provide higher plane of nutrition forhigh survival and rapid growth for rohu larva.     

Dietary inclusion of crystalline D- and L-methionine: effects on growth, feed and protein utilization, and digestibility in small and large Atlantic salmon (Salmon salar L.)

Use of crystalline methionine to optimize amino acid profiles in feeds for Atlantic salmon (Salmo salar L.) was studied in three experiments. A basic experimental diet with 25% of dietary protein from marine origin and the remaining 75% from soya protein concentrate was used either with or without supplementation of L ‐methionine, D ‐methionine or DL ‐methionine. A fishmeal‐based diet was used as control. In experiment 1, growth performance of 100 g salmon in seawater was improved by supplementation with the different methionine products. Growth performance was, however, inferior to that of fish fed the control. Feed conversion ratios (FCR) exhibited similar trends to specific growth rate (SGR) with methionine supplementation, but again not as the control. Protein retention, measured as productive protein value (PPV), was significantly better in the control and D ‐methionine groups as compared with either L ‐methionine or the nonsupplemented group. These trends were confirmed in experiment 2, using fish of the same size, where an absorption and digestibility study of D ‐ and L ‐methionine clearly indicated that D ‐methionine was absorbed as well as L ‐methionine. Results indicated that racemization of D ‐ into L ‐methionine occurs in liver and kidney in Atlantic salmon. Ornithine decarboxylase (ODC) activity in liver was significantly affected by dietary treatment and there was a good correlation with growth and feed utilization data. In experiment 3, a growth study with large salmon (1 kg) was performed using increasing supplementation of DL ‐methionine to the basic diet. Results indicated a methionine requirement for maximum growth of 9.2 g kg^–1 feed dry matter (DM) kg^–1 growth. This is slightly higher than that reported in the literature. The present study clearly shows that optimizing the amino acid profile by inclusion of a single crystalline amino acid (crystalline methionine) does not give the same protein utilization as that of a diet in which the amino acids are mainly protein bound. D ‐methionine was found to result in better protein utilization than L ‐methionine when measured as PPV.     

Effects of the protein/carbohydrate ratio of extruded diets on protein synthesis, protein growth and body composition in juvenile brown trout (Salmo trutta)

High levels of protein in fish feeds result in higher costs and nitrogen waste. Therefore, studies focused on protein substitution by alternative energy sources are necessary. Here we examine whether the protein:carbohydrate ratio in extruded diets affects protein-turnover parameters and the main tissue components in brown trout. Juvenile fish were adapted to two extruded diets: one higher in protein and lower in carbohydrate, C: 45/28 and the other higher in carbohydrate and lower in protein, HC: 37/40. Gross energy was 19 MJ kg⁻¹ DM in both diets. Protein and lipid digestibility were high and similar in both groups (≈90%), whereas total and carbohydrate digestibility and digestible energy were lower in the HC-fed group than in the C-fed group. Consequently, when fish were adapted to the diets, plasma levels of glucose and insulin differed between diets. HC-group presented higher plasma glucose levels and lower plasma insulin levels than C-group. Protein synthesis rates in white muscle, liver and whole body did not differ significantly between diets. In contrast, protein accretion rate of white muscle and whole body were significantly lower in the HC group, indicating an increase of protein degradation in these tissues and a decrease of synthesis retention efficiency. In spite of the daily protein intake of HC group was lower than C-group, the anabolic stimulation efficiency was increased by 34% in HC group. Protein and lipid contents in white muscle and liver were stable throughout the experiment. No hepatomegalia or increased fat deposition was observed in fish fed HC. Differences in specific growth rates (C: 0.88%; HC: 0.77%) were associated more with the lower protein consumption rate and the lower level of digestible energy in fish fed HC than with the higher dietary carbohydrate content of the diet.     

Improving cereal grain carbohydrates for diet and health

Starch and cell wall polysaccharides (dietary fibre) of cereal grains contribute to the health benefits associated with the consumption of whole grain cereal products, including reduced risk of obesity, type 2 diabetes, cardiovascular disease and colorectal cancer. The physiological bases for these effects are reviewed in relation to the structures and physical properties of the polysaccharides and their behaviour (including digestion and fermentation) in the gastro-intestinal tract. Strategies for modifying the content and composition of grain polysaccharides to increase their health benefits are discussed, including exploiting natural variation and using mutagenesis and transgenesis to generate further variation. These studies will facilitate the development of new types of cereals and cereal products to face the major health challenges of the 21st century.     

雷笋膳食纤维的制备工艺及其特性研究

以雷笋笋肉及加工后的下脚料笋壳等为原料,探讨了制取雷笋膳食纤维的最佳工艺条件。通过正交试验设计,采用绿色木霉发酵法制备雷笋膳食纤维,并对其化学成分、持水力、溶胀性、对重金属束缚能力等特性进一步研究。结果表明:最佳发酵条件为8%的接种量,于32℃,pH为7.0条件下培养48 h;产品的膳食纤维含量为85.23%,可溶性膳食纤维为30.43%,持水力和溶胀性分别达到7.82 g/g和689 mL/g,对重金属Cd2+和Pb2+的最大束缚量分别为38.8μmol/g和37.4μmol/g。     

Characterisation of the microbiota associated with intestine of Atlantic cod (Gadus morhua L.): The effect of fish meal, standard soybean meal and a bioprocessed soybean meal

Populations of aerobic heterotrophic bacteria present in the gastrointestinal (GI) tract of healthy Atlantic cod (Gadus morhua L.) fed three different diets, fish meal, standard or a bioprocessed soybean meal (BPSBM), were estimated using the dilution plate technique. A total of 944 isolates were characterised by biochemical and physiological properties and 425 isolates were identified further by sequencing the 16S rRNA genes. Our results showed that gut microbiota were affected by dietary manipulation. The GI tract of fish fed fish meal was dominated by Gram-positive bacteria of the genera Brochothrix and Carnobacterium. The Gram-negative bacteria Chryseobacterium spp. and Psychrobacter glacincola, and Gram-positive bacteria belonging to Carnobacterium, dominated in the digestive tract of fish fed soybean meal. In contrast to these results, genus Psychrobacter dominated in the GI tract when fish were fed BPSBM.Until recently, it was generally suggested that the gut microbiota of fish were less diverse than in homoeothermic animals. However, the present study identified several “new” bacterial species isolated from the alimentary tract of Atlantic cod. These “new” bacterial species are not normally isolated from the GI tract of fish. Based on our finding we suggest that the GI tract microbiota of fish might not be as simple as believed.Antagonistic activity of carnobacteria regarding inhibition of growth of two fish pathogens (Aeromonas salmonicida ssp. salmonicida and Vibrio anguillarum) was observed. However, some difference in the antibacterial activity of Carnobacterium spp. was observed. Whether this antagonistic activity has any effect in challenge studies will be discussed, especially in relation to the finding that the digestive tract is one of the major infection routes in fish.     

Effect of taurine supplemented practical diet on growth performance and taurine contents in whole body and tissues of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effect of dietary taurine on juvenile Japanese flounder was determined by feeding three taurine-supplemented experimental diets (TAU) and a commercial diet (CD) to evaluate a practical diet for juvenile Japanese flounder. Juvenile Japanese flounder were reared on the three experimental diets supplemented with taurine at 0, 0.5, 1.0% and CD. These diets were fed to juvenile Japanese flounder of an initial mean body weight of 0.2 g for 6 weeks at 20°C and the taurine contents of the whole body and tissues were analyzed. The final average body weight of juvenile Japanese flounder fed the 1.0% TAU was significantly higher than that of the other groups. Taurine contents in the whole body and tissues increased with the increase in dietary taurine level. These results indicate that juvenile Japanese flounder require at least 15 mg/g taurine in the diet, even though a combined mix of fish, krill and squid meal was the main protein source in the experimental diets.     

Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.     

Supply of tree-holes limits nest density of cavity-nesting birds in primary and logged subtropical Atlantic forest

Tree cavities are proposed to limit populations and structure communities of cavity-nesting birds. Although the greatest diversity of cavity-nesting birds is found in tropical and subtropical moist forests, little is known about how tropical logging affects the abundance of cavities or cavity-nesting birds. We compared the abundance of cavities and cavity nests between primary and selectively-logged subtropical moist Atlantic forest in Argentina, and conducted the first before-after controlled nest-box addition experiment to determine whether nest sites limit the breeding density of cavity-nesting birds in tropical or subtropical moist forest. Visual inspection of 86 cavities identified through ground-surveys revealed that only 19% were suitable for nesting birds, suggesting that cavity abundance may be overestimated in the literature on tropical forests. Suitable cavities were found in fewer than 1% of 1156 trees <60 cm dbh but 20% of 20 trees >100 cm dbh. Logged forest had half the basal area of primary forest, one third the density of large trees, nine times fewer cavities suitable for nesting birds, and 17 times fewer active nests. When we added nest boxes, nesting density increased on treatment plots but not on control plots in both logged and primary forest, suggesting that cavity supply can limit nest density even in relatively undisturbed forest. This is the first experiment to show how reduced cavity supply in logged tropical forest can limit breeding density of cavity-nesting birds. International initiatives such as forest certification should promote tropical timber management strategies that conserve large live cavity-bearing trees.