兰州鲇对4种饲料原料的离体消化率和酶解能力

采用离体消化法,测定了离体状态下兰州鲇(Silurus lanzhouensis)(278.6±26.7)g的胃、肠道及肝胰脏对鱼粉、豆粕、菜粕和棉粕等4种饲料原料的消化率和酶解速度。结果显示:离体状态下兰州鲇消化道各部位的消化能力和酶解能力依次为前肠、中肠、肝胰脏、后肠和胃。离体状态下,胃、肠道及肝胰脏对鱼粉的干物质和粗蛋白的消化率最高,其次为豆粕、菜粕和棉粕(P<0.05);对鱼粉的酶解速度最高,其次为豆粕、菜粕和棉粕。结果表明,兰州鲇前肠和中肠消化能力较强,饲料的消化主要集中在这两个部位;在离体状态下,鱼粉的蛋白易于被各部位酶解产生氨基酸,比其他3种饲料更易被兰州鲇吸收。     

Response of gastrointestinal melatonin,antioxidants, and digestive enzymes to altered feeding conditions in carp (<Emphasis Type="Italic">Catla catla</Emphasis>)

The purpose of present study was to ascertain whether the response of gastrointestinal (gut) melatonin to altered feeding conditions was related to the levels of different antioxidants and digestive enzymes in the same gut tissues of a sub-tropical carp (Catla catla). Accordingly, the fish were subjected to food deprivation for 4 or 8 days and separately to re-feeding for 4 or 8 or 12 days after deprivation of food for 8 days, and their gut tissue homogenates were used to measure the levels of melatonin, both enzymatic [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST)] and non-enzymatic [reduced glutathione (GSH)] antioxidants, as well as different digestive enzymes (α-amylase, cellulase, protease, and lipase). Notably, the gut levels of melatonin, SOD, CAT, GPx, and GST underwent gradual increase with the progress of food deprivation, but a sudden fall after restoration of food supply for 4 days and a rise thereafter. Conversely, the activity of all the digestive enzymes significantly decreased after deprivation of food, but started increasing when food supply was reinforced. Gut melatonin concentrations by showing a positive correlation with the titers of different antioxidants (in both food-deprived and re-fed fish groups) and a negative (in food-deprived fish) or a positive (in re-fed fish) correlation with the activity of each digestive enzyme underlined possible physiological interplay between them. Collectively, our findings lend support to the hypothesis that gut melatonin response to altered feeding conditions in carp might be associated with the oxidative status as well as the digestive functions of the gastrointestinal tissues itself.     

Digestion of larval American shad by cyprinids

Cyprinids have pharyngeal teeth for grinding food before swallowing and a continuous gut with no discrete stomach. This digestive tract structure, as well as the feeding behavior traits shown by cyprinids, makes it difficult to identify and measure the amount of food consumed by these fishes. The relations among quantity of food in cyprinid gut, time after feeding and predator size were described by log-linear multiple regression. The number of intact American shad (Alosa sapidissima (Wilson)) larvae eaten in laboratory experiments was estimated by extrapolating the regression for the amount of food in the gut over time for predators of various size. The numbers of larval American shad in guts of fish captured in the Juniata River, Pennsylvania, were not significantly different from those estimated with the equations derived from laboratory data. In view of their abundance in rivers and their potential digestion rate for larval fish, cyprinids can be expected to have a marked influence on reducing the numbers of larval American shad.     

Potential bioavailability of protein and lipids in feed ingredients for the three‐spot cichlid Amphilophus trimaculatus: An in vitro assessment

For the commercial culture of the three‐spot cichlid (Amphilophus trimaculatus), it is important to have available a set of protein and lipid ingredients suitable for feed manufacturing, which allow to optimize the culture at affordable costs. The in vitro digestibility was evaluated with pH‐stat technique, using stomach and intestine multi‐enzymatic extracts from A. trimaculatus juveniles. The digestion of protein ingredients was taken place both in acid and in alkaline conditions, quantifying the total of free amino acids at the end of the hydrolysis, whereas the digestion of lipid ingredients was taken place only in alkaline conditions. The digestive enzymes of this species showed a better affinity to raw materials of animal origin such as beef meal, fish meal and premium chicken meal, which presented better digestibility. The best lipid ingredient that could be used is the fish oil. However, it is possible to use ingredients from the plant sources, such as soy or cereals, and vegetable oils such as olive, corn or soy oil. It is necessary to complement this study in vitro with the digestibility analysis in vivo, in order to determine the inclusion percentages in feeds and costs and therefore to develop an efficient feed formulation for the aquaculture of A. trimaculatus.     

Gut melatonin response to microbial infection in carp <Emphasis Type="Italic">Catla catla</Emphasis>

The purpose of present study was to demonstrate the response of gut melatoninergic system to Aeromonas hydrophila infection for 3 or 6 days and search for its correlation with the activity of different antioxidative and digestive enzymes to focus their interplay under pathophysiological conditions in carp (Catla catla). Microscopic study of gut in infected fish revealed degenerative changes in the tunica mucosa and lamina propria layers with sloughed off epithelial cells in the lumen. The activity of each digestive enzyme was reduced, but the levels of melatonin, arylalkylamine-N-acetyl transferase protein, the key regulator of melatonin biosynthesis, and different enzymatic antioxidants in gut were gradually and significantly increased with the progress of infection. Gut melatonin concentrations in A. hydrophila challenged carp by showing a positive correlation with the activity of each antioxidative enzyme, and a negative correlation with different digestive enzymes argued in favor of their functional relation, at least, during pathological stress. Moreover, parallel changes in the gut and serum melatonin titers indicated possible contribution of gut to circulating melatonin. Collectively, present carp study provided the first data to suggest that endogenous gut melatonin may be implicated to the mechanism of response to microbial infections in any fish species.     

大眼鳜和斑鳜消化道组织结构的比较研究

大眼鳜(Siniperca kneri)和斑鳜(Siniperca scherzeri)的标本于2010年3-6月采集于嘉陵江合川段,用组织学方法和H.E染技术比较研究了大眼鳜和斑鳜消化道的组织结构。结果表明:消化道由黏膜、黏膜下层、肌层和浆膜组织所构成,食道上皮主要为复层扁平上皮、单层柱状上皮和少量杯状细胞组成。大眼鳜的消化道较斑鳜的发达,如食道的黏膜下层及杯状细胞、胃黏膜下层的厚度、幽门盲囊绒毛密集程度。两种鱼消化道变化的基本规律为从食道到胃黏膜层和黏膜下层逐渐增厚,从胃到前肠厚度减少。大眼鳜肠前段、中段和后段的杯状细胞密度、肠绒毛上皮的杯状细胞的大小及形态的发达程度都大于斑鳜。同时由于大眼鳜的肠道形态结构较斑鳜发达,以至在物理消化上也较斑鳜强。该研究为大眼鳜和斑鳜的保护和养殖提供一定的理论依据。     

No room for dessert: A mechanistic model of prey selection in gut‐limited predatory fish

Predatory fish structure communities through prey pursuit and consumption and, in many marine systems, the gadoids are particularly important. These predators have flexible feeding behaviours and often feed on large prey items. Digestion times of large prey are usually longer than handling times, and gut processing limits feeding rate at high prey density. Optimizing the gut content mix can therefore be an important behavioural strategy. Here, we develop a foraging model that incorporates gut processing and use the model to disentangle internal and external limitations on feeding in the omnivorous cod (Gadus morhua, Gadidae). We extend the traditional definition of prey profitability to consider prey digestive quality, which we quantify for prey of Northeast Atlantic cod populations. We find an important role for gut limitation; within a range of ecologically relevant temperatures and prey densities, predicted feeding rates were strongly reduced compared to feeding constrained by external factors only, and the optimal diet composition under gut limitation differed from predictions from traditional foraging theory. Capelin, a main prey of Northeast Arctic cod, had the highest digestive quality of all prey across ecosystems, but the cold temperatures in the Barents Sea strongly limited feeding rate by slowing down digestion. Baltic cod fed on a higher proportion of poor‐quality prey compared to the other populations, contributing to its slow growth in relation to water temperature. Gut limitation is particularly important to consider in foraging models for fish with many alternative prey species or fish occupying cold waters where digestion is slow.     

Enzyme‐producing bacteria isolated from fish gut: a review

Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme‐producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.     

鱼类消化道内分泌细胞概述及研究方法

消化道内分泌细胞能产生多种具有调节胃肠功能的胃肠激素。该类激素除了能促进胃肠对营养物质的消化与吸收外,还能控制摄食行为、调控消化道运动以及细胞营养作用,甚至能够影响其他一些内分泌腺的活动。了解肠道内分泌细胞的基本概况有助于深入地研究鱼类的消化生理,组织化学、免疫细胞化学和电子显微镜等技术是研究消化道内分泌细胞鉴别、定位以及形态学的重要方法,利用这些技术能够揭示鱼类消化道内分泌细胞的生物功能及作用机理,对研究鱼类摄食、消化和吸收等生理机制有重要意义。因此,本文综述了近年来国内外鱼类消化道内分泌细胞的研究进展及主要研究手段,旨在为鱼类消化生理学、内分泌学和营养学提供参考资料。     

鱼类消化道内分泌细胞概述及研究方法

消化道内分泌细胞能产生多种具有调节胃肠功能的胃肠激素。该类激素除了能促进胃肠对营养物质的消化与吸收外,还能控制摄食行为、调控消化道运动以及细胞营养作用,甚至能够影响其他一些内分泌腺的活动。了解肠道内分泌细胞的基本概况有助于深入地研究鱼类的消化生理,组织化学、免疫细胞化学和电子显微镜等技术是研究消化道内分泌细胞鉴别、定位...     

牙鲆幼鱼消化道内蛋白酶活性及食糜蛋白的GFP示踪

用添加绿色荧光蛋白（GFP）饲料投喂牙鲆,研究了不同消化时间内食糜在牙鲆消化道中的分布情况,采用福林一酚法测定了不同时间胃、前肠、中肠和后肠各组织黏液蛋白酶活性。结果表明,牙鲆在摄食后消化道蛋白酶活性随着食糜在消化道内的分布而变化,食物的刺激引起消化腺体分泌蛋白酶。牙鲆摄食后1h食糜达到中肠,胃和中肠蛋白酶活性与空腹相比迅速增高;食糜在5h时遍布整个消化道,此时胃蛋白酶活性几乎检测不出,而前肠蛋白酶活性迅速增高,5h达到最高,然后开始降低;8h时中肠蛋白酶活性一直很高,之后降低;而后肠直到12h其蛋白酶活性仍维持在较高水平,说明牙鲆这种消化道较短的鱼类其肠道比胃在蛋白质消化过程中发挥更重要的作用。     

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.     

卵形鲳鲶消化酶活性的研究I．成鱼和幼鱼消化酶活性在不同消化器官中的分布及其比较

比较研究了卯形鲳够（Trachinotus ovatus）成鱼和幼鱼阶段消化酶（蛋白酶、淀粉酶、脂肪酶）在不同消化器官中的活性。结果表明：1）成鱼蛋白酶在不同消化器官中的活性大小依次为胃〉前肠〉中肠〉幽门盲囊〉后肠〉肝;淀粉酶活性为前肠〉后肠〉幽门盲囊〉中肠〉肝〉胃;脂肪酶活性为前肠〉中肠〉后肠〉幽门盲囊〉肝〉胃。2）幼鱼蛋白酶在不同消化器官中的活性大小依次为胃〉肠〉幽门盲囊〉肝;淀粉酶活性为肠〉幽门盲囊〉肝〉胃;脂肪酶活性为肠〉幽门盲囊〉肝〉胃。3）成鱼不同消化器官中蛋白酶和淀粉酶的活性均小于幼鱼,成鱼胃和幽门盲囊的淀粉酶活性与幼鱼的差异显著;幼鱼胃脂肪酶活性大于成鱼,但其他器官的活性均小于成鱼。卵形鲳鳕幼鱼不同消化器官中的3种消化酶活性大小顺序与成鱼基本相似。     

Ontogeny of pepsinogen and gastric proton pump expression in red porgy (Pagrus pagrus): Determination of stomach functionality

The appearance of functionally developed gastric glands is commonly considered as the transition from the larval to the juvenile stage in fish, since it means the switch from the less efficient alkaline digestion to a more efficient acid digestion characteristic of adult specimens. From that moment, fish are supposedly able to better assimilate nutrients from inert diets. Acid digestion takes place by the action of pepsin activity and hydrochloric acid, both secreted by the gastric glands of the stomach. Pepsinogen is the precursor of pepsin which is converted into active enzyme by the action of hydrochloric acid secreted by the proton pump. The goal of this work was to asses the ontogeny of pepsinogen and gastric proton pump expression along larval development of red porgy using RT-PCR and in situ hybridization techniques. Firstly, red porgy specific pepsinogen and proton pump partial sequences were isolated. Amplification products presented 615 and 591 bp and were identified as pepsinogen IIb and the -subunit of the proton pump (H⁺/K⁺-ATPase) by sequencing, respectively. Both sequences were aligned to several predicted pepsinogen and proton pump polypeptides from different vertebrate species showing elevated homologies with them, especially in the case of the proton pump, the identity of which was never less than 90%. Pepsinogen and proton pump expressions were detected from 30 days post-hatching (dph), increasing with development. Proton pump expression was localized in the gastric glands of red porgy larvae as revealed by in situ hybridization, showing increasing signal intensity along the digestive system development. Such results indicated that at 30 dph red porgy starts to acquire the adult digestive capacity and therefore inert diets should be better utilized from that time onwards.     

达氏鳇和施氏鲟生长差异群体肠道菌群特征

同塘生长差异常常导致鲟养殖产量受损,而肠道菌群是影响鱼类生长性能的关键因素之一。为揭示肠道菌群与鲟科鱼类个体生长差异之间的关系,本研究对同批次繁育、同条件养殖的生长速率差异大于体重50%的达氏鳇(Huso dauricus)和施氏鲟(Acipenser schrencki)群体进行了肠道菌群特征研究。结果表明,达氏鳇和施氏鲟肠道菌群多样性和组成在种属间及生长差异群体间均具有明显差异。其中,生长快速达氏鳇群体(LH)肠道优势菌属为鞘氨醇单胞菌属(Sphingomonas,67.0%),生长慢速达氏鳇群体(SH)肠道优势菌属为鞘氨醇单胞菌属(29.5%)和狭义梭菌属1 (Clostridium sensu stricto 1, 54.2%);而生长快速施氏鲟群体(LA)肠道优势菌属为鞘氨醇单胞菌属(33.5%)和鲸杆菌属(Cetobacterium,38.1%),生长中速施氏鲟群体(MA)肠道优势菌属为鞘氨醇单胞菌属(42.6%)、狭义梭菌属1(14.3%)和鲸杆菌属(33.0%)。鞘氨醇单胞菌属和梭菌科(Clostridiaceae)细菌是不同生长速率鲟肠道中的主要差异类群。综上可知,鲟...     

Ontogeny and distribution of alkaline and acid phosphatases in the digestive system of California halibut larvae (Paralichthys californicus)

Studies aimed to assess the digestive physiology of marine fish larvae under culture conditions are important to further understand the functional characteristics and digestive capacities of the developing larvae. Most studies to date concentrate on intestinal lumen digestion and little attention to the absorption process. Thus, the objectives of this study were to histochemically detect and quantify some of the enzymes responsible for absorption and intracellular digestion of nutrients in the anterior and posterior intestine of California halibut larvae. Alkaline and acid phosphatases were detected from the first days post-hatch (dph). Alkaline phosphatase maintained a high level of activity during the first 20 dph in both intestinal regions. Thereafter, a clear intestinal regionalization of the activity was observed with the highest levels occurring in the anterior intestine. Acid phosphatase activity gradually increased in both intestinal regions during development, and a regionalization of the activity was not observed until late in development, once the ocular migration began. Highest levels were observed in the anterior intestine at the end of metamorphosis concomitant with the stomach development. The results from this study show some morphological and physiological changes are occurring during larval development and a clear regionalization of the absorption process as the larvae develops. These ontological changes must be considered in the elaboration of diets according to the digestive capacity of the larvae.     

Proteolytic enzymes in fish development and the importance of dietary enzymes

The development of proteolytic enzymes (trypsin, chymotrypsin and aminopeptidase) was studied in three species of fish: Coregonus sp. (hybrids of C. wartmanni and C. lavaretus from Lake Constance), Salmo gairdneri and Rutilus rutilus. Enzyme activity increased more or less with increasing age, particularly in R. rutilus. In this species (a stomachless cyprinid), the level of proteolytic activity was considerably higher than that of S. gairdneri and Coregonus. However, in trout, the low activity of pancreatic enzymes may be compensated by the action of the stomach whereas in coregonids the stomach is not developed until 50 days (body weight without gut content: 65 mg; temperature: 10°C) after hatching. In coregonids this may lead to insufficient digestion of proteins which nevertheless can be compensated by the use of exogenous (dietary) enzymes ingested together with the natural diet. In coregonid larvae fed with Moina sp., exogenous trypsin represents a very high portion of the total tryptic activity. In juveniles older than 60 days (> 150 mg) and in the other two species, the exogenous portion of tryptic activity is less important. Furthermore, a change in the pattern of tryptic isozymes has been found during development of coregonids. It is concluded that low enzyme production as well as the absence of a stomach in the first few weeks after hatching are two important reasons for difficulties in rearing coregonids on an artificial diet.     

Changes in digestive enzyme activities of red porgy Pagrus pagrus during a fasting–refeeding experiment

An experiment was carried out in red porgy, Pagrus pagrus (Teleostei, Sparidae), to assess the effects of a 14-day fasting period, followed by refeeding to apparent satiation, on the contents of digestive enzymes (total proteases, and particularly pepsin, trypsin, chymotrypsin, carboxypeptidases A and B; amylase and lipase). Two fish groups were considered: one (indicated as fasted/refed group) was fasted for 14 days and then refed during further 7 and 15 days, and the other was fed throughout the study and was taken as a control group. The measured enzymatic values showed that fasting resulted in a generalized, not significant decrease, of the activity of digestive enzymes. Refeeding caused a significant increase for most of the assayed enzymes: total proteases both in the middle and distal intestine, pepsin in the stomach, trypsin in the middle intestine, and amylase and lipase in the proximal intestine. Nevertheless, the detection in the fasted/refed fish of enzymatic values still lower than those measured in the control fish suggested that fish experiencing short-term fasting were partially impaired in their digestive capacity.     

An evaluation of open and closed systems for in vitro protein digestion of fish meal

The availability of a rapid, cost-effective, accurate and reliable method of assessing fish meal protein digestibility would greatly enhance and standardize quality-control procedures in both the fish meal and fish feed industries. However, while several in vitro digestibility tests have been developed, few have been adopted by industry due to their time-consuming nature, problems surrounding reliability and/or inconsistencies in predictive ability. The present investigation was undertaken to evaluate the utility and predictive qualities of two in vitro digestion assays of distinct design. Methods examined included a novel open system, wherein on-line removal of digestion products was attainable, and a closed system, which permitted analysis of products following completion of the digestion process. Results provided by the two systems were compared using four differentially processed fish meals. The open system supplied information based upon the detected quantity of products below 10 kDa. The closed system provided measurement of free amino groups. Both methods were in agreement with respect to assessing the presence of hydrolysed product. Both systems furnished complementary data with respect to the characterization of fish meal protein quality. The closed and open systems provided insight upon digestibility and digestion kinetic profiles respectively.     

Digestive protease characterization, localization and adaptation in blacklip abalone (Haliotis rubra Leach)

Digestive protease in blacklip abalone (Haliotis rubra Leach) from whole gut extracts was found to have dual pH optima at pH 3 and 10 and an optimum temperature of 45 °C. Over the biologically relevant range of pH (5–8), protease activity dropped to a minimum at pH 5 (53% of the maximal rate at pH 3) rising gradually and continuously up to (and beyond) pH 8. Over the biologically relevant range of temperatures (9–24 °C), protease activity increased continuously with activity at 24 °C being 75% higher than activity at 9 °C. Protease digestion was relatively uniform in gut extracts from sections containing gut contents. Digestion thus appears to be significantly extracellular (in the lumen of the gut). Analysis of gut sections washed free of food matter suggests the anatomical origin of protease from activity of gut regions in the order: digestive gland » salivary gland ≈ stomach > crop > intestine > upper oesophagus. Whole gut protease levels did not alter in response to a high protein artificial diet.