Food handling efficiency and particle size selectivity by the southern brown shrimp penaeus subtilis fed a dry pelleted feed

This study investigated the feed handling efficiency and size selectivity of four size groups of Penaeus subtilis fed three commercial feed particle sizes. Shrimp feeding behaviour was recorded with a video‐camera, installed below a glass aquarium, where one shrimp at a time was introduced and allowed to feed. A total of 163 specimens of P. subtilis were examined. Results indicated that over 59% of all food particles placed in the mouth by shrimp were completely or partially consumed, regardless of size. Large pellets however were less preferred than small ones. Manipulation capacity and capture success were also greater when shrimp were fed small particles. Shrimp size had no significant effect on manipulation efficiency, indicating that within the feed size range examined, food handling by juvenile shrimp was as efficient as adults. These results suggest that in aquaculture systems, the use of crumbles and broken pellets may be preferable to large pellets.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Characterization of pellet morphology during submerged growth of Streptomyces tendae by image analysis

Many filamentous bacteria and fungi tend to form pellets, or mixtures of dispersed mycelium and pellets in liquid fermentation broths. In some cases, a specific kind of morphology is required for optimum product yield. When quantitative analysis and characterization of the pellet morphology are needed, an image processing system can be used. It allows a fast and reproducible analysis of the frequency distribution of pellet size, mean pellet size, contents of pellets, or their shape. The use of such a system allows for an on-line analysis. For a demonstration of the method, results of two fermentations of Streptomyces tendae are shown.     

Ammonia removal from prawn aquaculture water using immobilized nitrifying bacteria

Intensive prawn aquaculture in tropical regions is associated with high concentrations of total ammoniacal nitrogen (TAN) as a result of high rates of prawn excretion and feed loading. Excessive TAN can adversely effect productivity and result in adverse impacts on coastal waters. Cultures of indigenous nitrifying bacteria were enriched from intensive prawn aquaculture pond water using continuous and batch enrichment techniques. Cultures were capable of TAN removal over a wide range of initial TAN concentrations - up to 200 mg/l. Cultures were immobilized onto porous clay pellets to enhance cell density and applied to culture medium and TAN-augmented pond water under aerobic conditions to determine TAN removal proficiency. Immobilized cultures were able to achieve a high TAN removal proficiency in pond water--even at a low density of 0.1 pellet per liter. A concentration of less than 0.5 mg TAN/l could be maintained under a fed-batch condition of 3.2 mg TAN/l per day, after an initial 2-day lag phase. A simplified and effective culture enrichment process was developed for culture immobilization onto pellets using TAN-augmented pond water. Overall, pellet immobilization of indigenous nitrifying bacteria represents a potentially effective TAN control system for prawn aquaculture in low-cost, but intensive tropical prawn farms.     

Efficacy of orally administered praziquantel against Zeuxapta seriolae and Benedenia seriolae (Monogenea) in yellowtail kingfish Seriola lalandi

We investigated the efficacy of praziquantel (PZQ) administered orally to yellowtail kingfish (Seriola lalandi in sea-cage aquaculture in South Australia) against the monogeneans Zeuxapta seriolae and Benedenia seriolae infesting gills and skin, respectively. PZQ was administered to fish by surface-coating feed pellets (Trial 1) or by direct intubation of the stomach (Trial 2). In both trials 4 daily doses were administered: 50 and 75 mg kg(-1) body weight (BW) d(-1) for 6 d, and 100 and 150 mg kg(-1) BW d(-1) for 3 d. Mean parasite intensity was compared between medicated fish and unmedicated control fish. In Trial 1, fish fed lower daily doses of PZQ for 6 d (50 and 75 mg kg(-1) BW d(-1)) had fewer Z. seriolae and B. seriolae than fish fed higher daily doses for 3 d (100 and 150 mg kg(-1) BW d(-1)). Fish rejected feed pellets surface-coated with PZQ, suggesting PZQ affected palatability of feed, and may explain differences in efficacy between treatments. In Trial 2, where PZQ was administered by intubation, there were fewer Z. seriolae and B. seriolae in medicated fish than control fish. Intubated PZQ was also effective against newly recruited Z. seriolae and B. seriolae. PZQ could be developed as a useful treatment for Z. seriolae and B. seriolae parasitising S. lalandi in sea-cage aquaculture if suspected palatability problems are resolved.     

A new feeder system for quantitating actual toxicant consumption by mice during feeding studies.

A new mouse feeder system was described which enables mice to be utilized for long-or short-term feeding studies of chemical toxicants. Quantitative toxicant consumption can be obtained. The use of granulated feed of particle size, 500-1000 mu, prevents bridging, thus assuring a constant supply of diet to the experimental animals. Comparative weight gain in female BALB/c Nctr BR mice showed no significant differences between the groups fed 500 ppm 2-fluorenylacetamide, control granulated feed, or pellets.     

Classification and measurement of fungal pellets by automated image analysis

An automated image analysis method for classifying and measuring pellets of filamentous fungi growing in submerged fermentations has been developed. The method discriminates between pelleted mycelial growth and loose aggregates of dispersed hyphae. Pellets are classified into smooth and hairy types. In both cases, the core of the pellet is identified and its shape and size characterized. For hairy pellets the annular region is also characterized. The method was tested on pellets of Aspergillus niger ATCC 11414 grown in a defined medium in shake flasks. This rapid method makes practical extensive studies on the morphology of pellets in submerged fermentations and the influence of fermentation conditions on that morphology.     

微生物发酵饲料在绿色养殖中应用的研究进展

微生物发酵饲料，目前是饲料工业和养殖业的关注热点之一，也是绿色安全养殖的重要条件。我国早在20世纪90年代开始研究。近年来，微生物发酵饲料在畜牧业生产中得到迅速发展，其生产和应用形式更加多样化。在水产畜牧养殖时，将日基础饲粮部分替换成微生物发酵饲料或经复合微生物发酵后直接饲用，因含有活菌及相关代谢产物，能进一步改善动物对饲料的营养吸收、提高动物的生产性能、防病治病和改善养殖环境。未来将在饲料替代抗生素、饲养高品质动物、畜禽防病等方面发挥必不可少的作用。本文阐释了微生物发酵饲料概念，作用机理及其在畜牧业、水产养殖应用中的最新研究现状，为微生物发酵饲料产品及新技术的研发提供参考。     

Towards Integrated Multi-Trophic Aquaculture: Lessons from Caprellids (Crustacea: Amphipoda)

The search for alternative live feed organisms and the progression of Integrative Multi-Trophic Aquaculture (IMTA) are currently being highly prioritised in EU strategies. Caprellids could potentially be an important exploitable resource in aquaculture due to their high levels of beneficial polyunsaturated fatty acids, fast growing nature and widespread distribution. Furthermore, since they are mainly detritivorous, they could be excellent candidates for integration into IMTA systems, potentially benefitting from uneaten feed pellets and faeces released by cultured fish in fish farms and sea-cage structures. Despite this, there is a lack of experimental studies to: (i) test inexpensive diets for caprellids, such as detritus, (ii) develop sustainable caprellid culture techniques and (iii) include caprellids in IMTA systems. The main aim of this study was to determine whether detritus (D) in the form of fish faeces provided an adequate diet for caprellids in comparison to other traditional diets, such as Artemia nauplii (A) or phytoplankton (P). Adult survival rate was shown to be significantly higher for caprellids fed with D. Conversely, hatchlings had the highest survival rate with A, although the juvenile growth rate and number of moults was similar in the three diets. With regard to lipid composition, caprellids fed with A had higher concentrations of Triacylglycerols (TAG) and Phosphatidylcholine (PC) while those fed with P or D were richer in polyunsaturated fatty acids, especially 22:6(n-3) (DHA). Interestingly, caprellids fed with D were also a rich source of 18:2(n-6) (LA), considered to be an essential fatty acid in vertebrates. It was found that detritus based mainly on fish faeces and uneaten feed pellets can be considered an adequate feed for adult caprellids, providing a source of both omega-3 (DHA) and omega-6 (LA) fatty acids. Hatchlings however seem to require an additional input of TAG and PC during juvenile stages to properly grow.     

基于帧间光流特征和改进RNN的草鱼摄食状态分类

针对鱼类连续摄食行为较难识别与量化的问题, 提出一种基于帧间光流特征和改进递归神经网络(Recurrent neural network, RNN)的草鱼摄食状态分类方法。首先利用偏振相机搭建户外池塘采样系统, 采集不同偏振角度水面图像, 并基于图像饱和度和亮度模型自动选择低反光角度图像, 构建图像样本库; 其次通过光流法提取帧间运动特征, 并基于投饲机开关状态构建时间序列帧间特征样本集, 然后利用样本集训练改进RNN分类网络。以上海市崇明区瑞钵水产养殖专业合作社的试验数据对该方法进行验证。结果表明, 研究方法综合准确率为91%, 召回率为92.2%, 均优于传统的鱼类摄食行为识别方法。研究结果可为鱼类精准投喂技术研究提供参考。     

The use of probiotics in aquaculture

This study aims to present comprehensive notes for the use of probiotics in aquaculture. Probiotics have been proven to be positive promoters of aquatic animal growth, survival and health. In aquaculture, intestines, gills, the skin mucus of aquatic animals, and habitats or even culture collections and commercial products, can be sources for acquiring appropriate probiotics, which have been identified as bacteria (Gram‐positive and Gram‐negative) and nonbacteria (bacteriophages, microalgae and yeasts). While a bacterium is a pathogen to one aquatic animal, it can bring benefits to another fish species; a screening process plays a significant role in making a probiotic species specific. The administration of probiotics varies from oral/water routine to feed additives, of which the latter is commonly used in aquaculture. Probiotic applications can be either mono or multiple strains, or even in combination with prebiotic, immunostimulants such as synbiotics and synbiotism, and in live or dead forms. Encapsulating probiotics with live feed is a suitable approach to convey probiotics to aquatic animals. Dosage and duration of time are significant factors in providing desired results. Several modes of actions of probiotics are presented, while some others are not fully understood. Suggestions for further studies on the effects of probiotics in aquaculture are proposed.     

Total ammonia nitrogen leaching from feed pellets used in salmon aquaculture

The total amount of ammonia nitrogen (TAN) leaching from Atlantic salmon ( Salmo salar L.) feed pellets was determined under controlled laboratory conditions. The leaching was successfully explained by means of a first order kinetic equation:     , where a was the maximum TAN leached and k was the velocity of the process. Then t _a was defined as the time at which a was reached, which was obtained from the equation prediction. The interaction between pellet size and immersion length significantly influenced TAN leaching: the smaller the pellet and the longer the immersion times, the higher the leaching ( a ). However, pellet size did not influence k or t _a , although k tended to be higher and t _a lower for larger pellets. TAN leaching from feed pellets depends on the protein content and contact surface. As the surface/volume ratio (S/V) increases with pellet size while the protein content decreases, it was hypothesized that S/V influences k whereas the protein content has a greater effect on a .     

水产养殖饲用微生态制剂研究进展

微生态制剂作为新型饲料添加剂,能够有效调节水产动物营养保健和微生态平衡,减少抗生素使用,是理想的抗生素替代品,对保障高效种养殖、食品安全及环境可持续发展意义重大。我国饲用微生态制剂应用起步较晚且发展较慢,仍面临着难点和挑战。本文介绍了微生态制剂及饲用益生菌在鱼、虾及海参养殖中的应用,基于优良益生菌选育、培养条件优化及混合菌株发酵与制剂应用等生物技术研究现状,总结了近年来水产养殖饲用微生态制剂的研究进展,并对未来微生态制剂研究重点和发展前景进行了展望。     

Risk allocation and competition in foraging groups: reversed effects of competition if group size varies under risk of predation

Animals often feed more quickly when in larger groups. This group-size effect is often explained by safety advantages for groups but an alternative explanation is that animals feed faster in larger groups because of greater scramble competition for limited food. We show that predation risk enhances the group-size effect if groups vary in size. By contrast, competition leads to the group-size effect only when individuals feed in groups of constant size. When individuals feed in groups that vary in size, the best strategy for dealing with competition is to feed intensely when in smaller groups and feed little when in larger (more competitive) groups. In all situations, the effects of competition interact with the effects of predation risk in a simple multiplicative way. Our results suggest that scramble competition is not a general explanation for the group-size effect on vigilance in situations where group size changes relatively rapidly.     

Can adult and juvenile European rabbits be differentiated by their pellet sizes?

Recently, a new method for differentiating juvenile and adult rabbits based on faecal pellet size was published. According to this method, pellets >6 mm diameter are inferred to be deposited by adults, while those <6 mm are inferred to be from juveniles or kittens. In this study, we designed a simple experiment to test the accuracy of this methodology. Twelve adult rabbits were housed in individual outdoor cages and their pellets were removed every day for 10 consecutive days. Pellets were separated using a sieve according to their size and counted. Results showed that adult rabbits produce pellets >6 mm diameter in the same proportion as those <6 mm. We also observed a strong influence of the individual rabbit on pellet size; some rabbits produce a high proportion of pellets >6 mm, whereas others deposit mostly pellets <6 mm in size. Our findings demonstrate that pellet size is unsuitable for aging wild rabbits. Field biologists should therefore be cautious when employing the pellet size method of age determination in other wild animals in the absence of validating studies.     

IMPACT OF ALGAL RESEARCH IN AQUACULTURE

Algal aquaculture worldwide is estimated to be a $5–6 billion U.S. per year industry. The largest portion of this industry is represented by macroalgal production for human food in Asia, with increasing activity in South America and Africa. The technical foundation for a shift in the last half century from wild harvest to farming of seaweeds lies in scientific research elucidating life histories and growth characteristics of seaweeds with economic interest. In several notable cases, scientific breakthroughs enabling seaweed-aquaculture advances were not motivated by aquaculture needs but rather by fundamental biological or ecological questions. After scientific breakthroughs, development of practical cultivation methods has been accomplished by both scientific and commercial-cultivation interests. Microalgal aquaculture is much smaller in economic impact than seaweed cultivation but is the subject of much research. Microalgae are cultured for direct human consumption and for extractable chemicals, but current use and development of cultured microalgae is increasingly related to their use as feeds in marine animal aquaculture. The history of microalgal culture has followed two main paths, one focused on engineering of culture systems to respond to physical and physiological needs for growing microalgae and the other directed toward understanding the nutritional needs of animals—chiefly invertebrates such as mollusks and crustaceans—that feed upon microalgae. The challenge being addressed in current research on microalgae in aquaculture food chains is to combine engineering and nutritional principles so that effective and economical production of microalgal feed cultures can be accomplished to support an expanding marine animal aquaculture industry.     

Abrasion of suspended biofilm pellets in airlift reactors: importance of shape, structure, and particle concentrations

The detachment of biomass from suspended biofilm pellets in three-phase internal loop airlift reactors was investigated under nongrowth conditions and in the presence of bare carrier particles. In different sets of experiments, the concentrations of biofilm pellets and bare carrier particles were varied independently. Gas hold-up, bubble size, and general flow pattern were strongly influenced by changes in volume fractions of biofilm pellets and bare carrier particles. In spite of this, the rate of biomass detachment was found to be linear with both the concentration of biofilm pellets and the bare carrier concentration up to a solids hold-up of 30%. This implies that the detachment rate was dominated by collisions between biofilm pellets and bare carrier particles. These collisions caused an on-going abrasion of the biofilm pellets, leading to a reduction in pellet volume. Breakage of the biofilm pellets was negligible. The biofilm pellets were essentially ellipsoidal, which made three-dimensional size determination necessary. Calculating particle volumes from two-dimensional image analysis measurements and assuming a spherical shape led to serious errors. The abrasion rate was not equal on all sides of the biofilm pellets, resulting in an increasing flattening of the pellets. This flattening was oriented with the basalt carrier inside the biofilm and independent of the absolute abrasion rate. These observations suggest that the collisions causing abrasion are somehow oriented. The internal structure of the biofilms showed two layers, a cell-dense outer layer and an interior with a low biomass density. Taking this density gradient into account, the washout of detached biomass matched observed changes in volume of the biofilm pellets. No gradient in biofilm strength with biofilm depth was indicated. (c) 1997 John Wiley & Sons, Inc.     

Enthalpy content as a function of lipid accumulation in Rhodotorula glutinis

Microcalorimetry has been demonstrated to be a suitable on-line method for monitoring the lipid production phase of oleaginous yeasts. The choice of lipid extraction method for the oil accumulated by oleaginous yeasts is highly important both for accuracy when quantifying the lipid level and determining the fatty acid composition. The energy content of Rhodotorula glutinis increased from 23.0 kJ/g to 30.6 kJ/g dry biomass during the lipid-accumulating phase and was directly correlated to the analysed level of lipids, when an alkaline hydrolysis extraction method was used. Consequently, bomb-calorimetric measurements of the energy content were shown to be an indirect method of quantifying the lipid content in oleaginous yeasts. The fatty acid composition remained rather constant during the batch growth of Rh. glutinis with approximately 70% unsaturated C18 fatty acids. The high energy content as well as the fatty acid composition of Rh. glutinis makes this yeast a better candidate for use as aquaculture feed compared with the commonly used Saccharomyces cerevisiae.