Tissue essential fatty acid composition and competitive response to dietary manipulations in white bass (Morone chrysops), striped bass (M. saxatilis) and hybrid striped bass (M. chrysopsxM. saxatilis)

The effects of wide changes in dietary levels of docosahexaenoic (DHA) or arachidonic (ArA) acids on growth, survival and fatty acid composition in body tissues of Morone larvae were examined. White bass (WB, Morone chrysops), striped bass (SB, Morone saxatilis) and sunshine hybrid bass (HSB, M. chrysopsxM. saxatilis) larvae (day 24-46) were fed Artemia nauplii enriched with algal sources of varying proportions of DHA and ArA (from 0 to over 20% of total fatty acids). WB larvae fed DHA-deficient Artemia diet retarded over 50% of their potential growth, however, increasing dietary DHA/ArA ratios were associated with a significant growth improvement. The highest proportion of polyunsaturated fatty acids was found in WB neural tissue (approx. 50% of total fatty acids), while HSB neural tissue contained the highest proportion of saturated fatty acids (approx. 35% of total fatty acids). Within the neural tissues of all Morone larvae, both DHA and ArA were generally the most dominant as well as the most responding fatty acids to dietary manipulations (except in WB fed DHA or ArA deficient diets). HSB neural tissue was particularly efficient in retaining a significant amount of DHA in the face of dietary deficiency. However, WB neural tissue was the most responsive to dietary increase in DHA, accumulating a significantly higher amount of DHA (P<0.05) than SB or HSB. Results demonstrate significant differences in fatty acid composition and growth responsiveness to dietary manipulations between Morone larvae species and within specific tissues. WB weight gain and neural tissue composition was affected most by dietary changes in both DHA and ArA whereas SB and HSB tissue compositions were generally less affected by dietary manipulations.     

Herbal supplementation diets on hematology and innate immunity in goldfish against Aeromonas hydrophila

Goldfish, Carassius auratus (47 ± 3 g, n = 300) were inoculated intramuscularly (50 μl) with Aeromonas hydrophila (1.8 × 10⁶ cells ml^?1). On the 6th day of post-infection the fishes were divided into i) control, without infection fed with normal diet (C), ii) infected fish, fed with normal diet (IU), and infected fishes treated with different doses of iii) 100 mg kg^?1, iv) 200 mg kg^?1, iv) 400 mg kg^?1 and vi) 800 mg kg^?1 mixed herbal extracts supplementation diets. Hematological and immunological parameters were determined on week 1, 2 and 4. In infected goldfish were fed diets containing 100 and 200 mg kg^?1 of mixed herbal extracts supplementation feeds, the white blood cell (WBC) levels significantly increased (P < 0.05) throughout the experimental trial compared to the control. During the experimental period, the red blood cell (RBC) and haemoglobin (Hb) level in goldfish significantly decreased (P < 0.05) when fish fed with 100 and 200 mg kg^?1 of mixed herbal extracts supplementation feeds while it was restored near control when infected fish fed with 400 or 800 mg kg^?1 of herbal extracts supplementation feeds. On the other hand, the haematocrit (Ht) values decline significantly (P < 0.05) in 100, 200 and 400 mg kg^?1 of mixed herbal supplementation feeding groups on weeks 2 and 4 when compared to control group. The mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) values almost significantly differ from the control values. The infected goldfish and treated with 100 or 200 mg kg^?1 of herbal supplementation feeds exhibited significantly decline (P < 0.05) in total protein (TP), glucose (GLU) and cholesterol (CHO) levels on week 1–4 whereas it was restored when infected fish fed with 400 or 800 mg kg^?1 of herbal supplementation feeds on week 4. In comparison to untreated control goldfish, the respiratory burst activity and phagocytic activity of blood cells was significantly enhanced in infected fish feeding with 200, 400 and 800 mg kg^?1 of herbal supplementation feeds compared to the control. On the other hand, infected fish fed with all the doses of mixed herbal supplementation feeds, the lysozyme activity was significantly enhanced throughout the experimental period. This study shows that the infected goldfish treated with 400 and 800 mg kg^?1 of herbal supplementation feeds preceding the challenge with live A. hydrophila had 30% and 25% mortality. However, 100 and 200 mg kg^?1 of herbal supplementation feeds treated groups were found the percentage mortality 50% and 45%, respectively. Our results indicate that 400 or 800 mg kg^?1 of mixed herbal supplementation feeds were restored the altered hematological parameters and triggering the innate immune system of goldfish against A. hydrophila.     

Improved survival and growth of silver therapon Leiopotherapon plumbeus early juveniles through co-feeding with Artemia and commercial feeds

This study examined the effects of co-feeding Artemia and commercial feeds on survival, growth and fatty acid composition of silver therapon Leiopotherapon plumbeus early juveniles. Triplicate groups of 36 days post hatch (DPH) early juveniles (17.09 ± 1.69 mm; 0.07 ± 0.02 g) were stocked in nine glass aquaria at 25 individuals per aquarium and reared for 60 days on three feeding regimes: (A) Artemia + powdered commercial tilapia feed (35% crude protein (CP)); (B) Artemia + powdered commercial prawn feed (38% CP); and (C) Artemia nauplii only as the control group. Early juveniles co-fed Artemia and commercial feeds had significantly higher survival (97%) than those fed Artemia alone (86%). Except for the condition factors that were similar to the control group, higher mean total length (30.2 ± 1.3 mm and 27.6 ± 1.2 mm), body weight (401 ± 64 mg and 339 ± 46 mg), length- (SGRL; 0.95 ± 0.07%/day and 0.80 ± 0.07%/day) and weight-specific growth rates (SGRW; 2.85 ± 0.27%/day and 2.58 ± 0.22%/day) were also observed in the co-feeding groups, independent of protein, fat and other nutrient levels in commercial feeds. Higher levels of long-chain polyunsaturated fatty acids were reflected in early juveniles co-fed Artemia and commercial feeds than those fed exclusively on Artemia contributing, in part, to the higher growth and survival observed in the co-feeding groups. Together, these results suggest that co-feeding strategy showed best results in terms of growth and survival, and that commercial feed with 35% protein and 6% crude fat levels may be beneficial in supplementing live feed with essential nutrients to optimize production of silver therapon fry during nursery culture.     

Food consumption and retention time in captive whooping cranes (Grus americana)

Food consumption, digesta retention time, and food preference were measured for captive whooping cranes fed pelleted diets. The basal commercial diet was compared to four mixtures containing 70% basal and 30% of one of four important winter foods for the whooping crane: blue crab (Callinectes sapidus), wolfberry fruit (Lycium carolinianum), live oak acorn (Quercus virginiana), or common Rangia clam (Rangia cuneata). Because captive birds would not eat whole foods, we were prevented from direct food preference tests. Food passed through the gut rapidly, with almost complete elimination within 7 hr. There was some indication that retention time was shorter for the low fiber and high ash and calcium clam diet. Cranes ate less wolfberry feed (g/day) than the other feeds, and all birds ate less wolfberry feed on the day it was first fed, compared to basal diet the previous day. Birds ate more low energy feed than high energy feed. Due to combined effects of low energy content, lower metabolizable energy coefficients, and reduced feed consumption, less energy was assimilated for study diets than basal diet. Apparent shorter retention times for some diets containing whooping crane foods may partly explain lower digestibilities and metabolizable energy of winter whooping crane foods compared to commercial crane diet. Zoo Biol 16:519–531, 1997. © 1997 Wiley-Liss, Inc.     

Effects of feeding rate on the growth performance of gynogenetic albino sterlet,Acipenser ruthenus (Linnaeus, 1758) larvae

The feeding rate effects were studied on the growth performance of gynogenetic diploid larvae of sterlet Acipenser ruthenus during the first 4 weeks of exogenous feeding. The experimental rearing was conducted from 7 to 38 days post‐hatch (dph) in a circulation system. This was set up in four groups with three replicates (440 individuals/replicate), viz: AC‐control larvae fed Artemia sp., CFC‐control larvae fed compound feed, AG‐gynogenetic larvae fed Artemia sp., and CFG‐gynogenetic larvae fed compound feed. The larvae were reared in glass tanks (44 L volume, 10 individuals/L) with the temperature maintained at 18 ± 0.5°C, photoperiod of 12L:12D and water flow regime of 1‐L/min and fed 50%, 25%, 25%, and 9% of their total biomass/day during feeding. Highest TL and WBW of gynogenetic diploid larvae (AG) were observed with 50.6 ± 1.2 mm and 607.3 ± 36.1 mg (n = 30) at 38 dph. Highest TL and WBW of control larvae (AC) were recorded with 49.5 ± 3.8 mm and 600.8 ± 88.0 mg (n = 30), respectively, with 73.1% ± 11.4% survival; the lowest survival rate was at 46.4% ± 7.1% (n = 30) for the CFG group. The results indicate that the gynogenetic and normal larvae of sterlet fed with live food (Artemia nauplii) from 7 dph can achieve higher growth and survivability compared to the larvae fed with formulated test feed. Results of this study suggest that the effective rearing of sterlet larvae from 7 to 38 dph strongly depends upon the types of feed rather than the genome manipulation performed.     

SPME‐GC/MS Analysis of Volatile Compounds Contained in the Insect Larvae of Tenebrio molitor and Leptinotarsa decemlineata before and after Using Insecticides

The larvae of two harmful insect species Tenebrio molitor and Leptinotarsa decemlineata were analyzed. The insects were sprayed with insecticides containing the active substances cyfluthrin and deltamethrin (T. molitor), and thiamethoxam and acetamiprid (L. decemlineata). The sprayed insect larvae were left for 24, 48 and 72 h. Samples were then prepared using SPME fiber to identify the volatile compounds contained in the larvae. The determinations were made by gas chromatography coupled with mass spectrometry (GC/MS). Chemical compounds were found in the analyzed samples: alkanes, aldehydes, ketones, esters, terpenes, fatty acids. In the samples prepared from T. molitor larvae, more than 20 % of aldehydes and 8–41 % of alkanes were determined. In the samples from L. decemlineata, fatty acids were 8–65 % depending on the length of time after applying the insecticide.     

Improvement of nutritional quality of cultured sobaity sea bream,Sparidentex hasta (Valenciennes) muscle by preharvest feeding of finisher feeds

A 6‐month long study was conducted to improve the nutritional quality of the cultured sobaity bream, Sparidentex hasta by feeding them finisher feeds containing high docosahexaenoic acid (DHA) at the last two months of the grow‐out stage so that the muscle DHA level be increased at par to the wild. A grow‐out feed used from the beginning until the end of the trial was considered as the control (Diet 1). Experimental diets 2 and 3 were formulated to contain 9.0% DHA (e.g. 1.68 g DHA/100 g feed) and 10.5% DHA (2.20 g DHA/100 g feed), by incorporating high DHA tuna oil into a sea bream grow‐out diet. For comparison, a commercial finisher feed (Diet 4) from Skretting, Italy was also used. The results of this study demonstrated that fish fed DHA enriched finisher diets resulted in significantly (p < .05) better growth, feed utilization and higher muscle eicosapentaenoic acid (EPA) and DHA content compared to those fed grow‐out diet. The muscle DHA and EPA of fish fed finisher diets were also higher than those of the whole year average DHA and EPA content of wild sobaity. An organoleptic evaluation showed no significant (p > .05) differences between sensory attributes of muscle from cultured and wild sea bream. The results of the study demonstrated that feeding finisher feed enriched with DHA at the later part of the grow‐out operation, the n‐3 PUFA levels of cultured sobaity can cost‐effectively be increased at par to the wild.     

Extraction of chitin and chitosan from larval exuvium and whole body of edible mealworm,Tenebrio molitor

The purpose of this study was to investigate the production of chitin and chitosan from both the exuvium and whole body of mealworm (Tenebrio molitor) larvae. Chitin from the exuvium and whole body of T. molitor larvae was chemically extracted with acid and alkali solutions to achieve demineralization (DM) and deproteinization (DP), respectively. The average DM (%) and DP (%) on a dry weight (DW) basis was 32.56 and 73.16% from larval exuvium, and 41.68 and 91.53% from whole body, respectively. To obtain chitosan, chitin particles from the exuvium and whole body of T. molitor larva were heated at various temperatures in different concentrations of NaOH. Average chitin yields were 18.01% and 4.92% of DW from the exuvium and whole body, respectively. The relative average yield of chitosan from whole body was 3.65% of DW. On average, over 90% of chitosan derived from whole body was deacetylated. The viscosity of chitosan from whole body was ranged from 48.0 cP to 54.0 cP. The chitin content of dry and wet byproducts from whole body were 17.32% and 16.94% respectively, compared to dry weight. The chitosan contents of byproducts on a DW basis were 14.48% in dry and 13.07% in wet byproduct. These results indicate that the exuvium and whole body of T. molitor larva may serve as a source of chitin and chitosan for use in domestic animal feed.     

Stocking rate and organic waste type affect development of three Chrysomya species and Lucilia sericata (Diptera: Calliphoridae): Implications for bioconversion

Fly larvae can be used effectively to reduce various organic waste types and produce value-added products, including protein as an ingredient in livestock feeds and oil for biodiesel production. However, fly development on different waste types may cause differences in growth rate and the body composition, which can further be influenced by fly species and their stocking rate. This study explored the impact of different waste types (kitchen waste, abattoir waste and swine manure) and larval stocking rate on growth and body composition of four blowfly species, Chrysomya chloropyga (Wiedemann), Chrysomya megacephala (Fabricius), Chrysomya putoria (Wiedemann) and Lucilia sericata (Meigen). First-instar larvae (20, 50 or 100), less than 3 hr old, were placed on 100 g of each waste type. Pre-pupal mass at commencement of post-feeding larval dispersal, time to onset of dispersal, survival and nutrient reserves were determined for each species, stocking rate and waste type. Our results revealed that larvae fed kitchen and abattoir waste had significantly higher dry mass, crude protein and lipid content compared with those fed swine manure. Higher survival rate was observed with increasing larval stocking rate. We provide important information to guide the mass production of high-quality nutrient-rich larvae and recommend C. putoria, which is versatile and effective on a range of waste products, as well as high in protein and lipids. The implications for waste management are discussed.     

取食聚苯乙烯塑料对黄粉虫幼虫肠道微生物群落的影响北大核心

随着塑料在人类社会中的普及,越来越多的废弃塑料及其前体物质被遗留在环境中,且其在自然环境中的降解速度十分缓慢,为此寻找有效的降解途径成为亟待解决的科学问题。【目的】探究利用黄粉虫(Tenebrio molitor)幼虫取食聚苯乙烯对其肠道微生物种群及其代谢路径的响应,以期通过食物诱导寻找一条生物降解和利用聚苯乙烯的有效途径。【方法】以聚苯乙烯为唯一食物来源喂饲黄粉虫幼虫,通过测量幼虫存活率和个体的体重来测定其生长发育情况;通过对其肠道内容物进行16S rRNA基因测序,分析其肠道菌群结构的变化;采用京都基因与基因组百科全书(Kyoto encyclopedia of genes and genomes,KEGG)分析法来预测相关功能基因。【结果】取食聚苯乙烯黄粉虫幼虫存活率和体重均下降,聚苯乙烯塑料明显减少;取食聚苯乙烯的黄粉虫幼虫肠道菌群丰度与多样性明显减少,在门水平,取食聚苯乙烯的黄粉虫幼虫肠道的优势菌为变形菌门(Proteobacteria)、软壁菌门(Tenericutes)和厚壁菌门(Firmicutes);在属水平,取食聚苯乙烯的黄粉虫幼虫肠道优势菌为螺旋体菌属(Spiroplasma)、肠杆菌(Enterobacillus)和大肠埃氏-志贺氏菌(Escherichia-Shigella);通过KEGG功能预测,找到与芳香类和烷烃降解功能相关的基因共18种,取食聚苯乙烯组黄粉虫幼虫肠道菌群降解聚苯乙烯相关通路丰度升高,相关基因表达增强。【结论】聚苯乙烯可以为黄粉虫幼虫生长发育提供一定的物质和能量,且能够使其完成一个世代过程;幼虫长时间取食单一食物后,其肠道菌群结构会发生目标性变化,利用KEGG预测能够找到与聚苯乙烯代谢相关的基因,为后续研究工作提供了有价值的依据。     

Effect of dietary Ptecticus tenebrifer powder on the fatty acid profile of egg yolk in laying hens

The poultry industry needs alternative feeds with no adverse effects on animal performance and egg quality. Insects represent effective animal feeds. However, Ptecticus tenebrifer (PT) has rarely been studied as an effective feed in terms of fatty acid contents. Therefore, we investigated the effect of dietary PT powder on the fatty acid profiles of egg yolks in laying hens. A total of 180 Hy-Line brown hens were divided equally into three groups (n = 60), with three replicates: the control group and two groups fed 2% and 4% PT powder, respectively. After 2 weeks, minor effects (P < 0.05) on oleic acid, dihomo-gamma-linolenic acid, and total monounsaturated fatty acids were observed among the groups. After 4 weeks, docosahexaenoic acid, docosapentaenoic acid, myristic acid, oleic acid, and total polyunsaturated fatty acids were slightly altered in the treatment groups (P < 0.05). For other fatty acids, the 2% and 4% PT groups had fatty acid concentrations similar to those of the controls. No differences in total n-6 and total n-3 were observed among the groups. In conclusion, using 2% and 4% PT powders did not notably change the fatty acid profiles of egg yolks and could replace some layer-hen feed without negative effects.     

Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed

The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5–30 mL^?1 water) during feeding. The unfed larvae had 100% mortality by days 11–13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5–10 mL^?1) and Panagrellus (50 mL^?1) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum), Panagrellus (50–100 mL^?1 per feeding) orArtemia (5 nauplii mL^?1 per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL^?1 per feeding), Panagrellus alone (100 mL^?1 per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia. The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.     

Substrate influence on physiology and virulence of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> acting on larvae and adults of <Emphasis Type="Italic">Tenebrio molitor</Emphasis>

Two isolates of Beauveria bassiana, wild type (wt) and its mutant type (mt) were compared in terms of growth patterns on culture plates containing media based on wheat bran, grasshopper exoskeletons, colloidal chitin or Sabouraud-dextrose agar (SDA). Germination for the mt isolate was up to 33% faster in all media. Influence of media on virulence was determined against larvae and adults of Tenebrio molitor. Mortality higher than 90% was reached for adults after 6 days using conidia from all media. For larvae, a mortality of 80% was reached after 11 days with conidia collected from SDA medium and between 15 and 35% with conidia from other media. In SDA medium, conidial yield was almost ten times higher for the mt isolate compared to the wt isolate; however, virulence traits were similar against either larvae or adults. These results may influence commercial preparations of entomopathogenic fungi based on conidia.     

Effect of nematode Panagrellus redivivus density on growth, survival, feed consumption and carcass composition of bighead carp Aristichthys nobilis (Richardson) larvae

The study aimed to determine the optimum density of free‐living nematodes in feeding bighead carp, Aristichthys nobilis, larvae. In the first experiment, carp stocked at 25 larvae L^?1 were fed varying levels of nematodes (50, 75, 100, 125 and 150 per ml) twice a day for 21 days from the start of exogenous feeding. Final body weight was significantly higher (P < 0.05) in larvae fed 125 and 150 nematodes per ml than in those fed 50 and 75 per ml, but survival was low (61.8 and 63.6%, respectively). Survival rate was highest in larvae fed 100 nematodes ml^?1 (81.3%). Carcass analysis showed that larvae fed 125 and 150 nematodes ml^?1 had significantly lower body protein and higher body lipid than those fed other nematode densities. Carcass ash was similar for larvae fed 50–100 nematodes ml^?1 but it decreased significantly at the higher nematode densities. Carp larvae in a subsequent experiment were given 50, 75 and 100 nematodes ml^?1 per feeding. Newly hatched Artemia was the control feed. Nematode consumption and growth of the larvae were determined. Larvae were sampled at intervals of 2–4 days and the nematodes in the gut were counted and measured. At each nematode density, the number of nematodes present in the gut of the larvae increased significantly with time. At each sampling day, the number of nematodes in the gut did not differ significantly among treatments (P > 0.05) although it tended to increase with nematode density at day 2 and day 4 but decrease at day 7 onward. The carp larvae consumed significantly shorter nematodes on day 2 and day 4 than on the succeeding sampling days regardless of nematode density. However, the length of nematodes in the gut of the larvae did not differ significantly among the nematode densities. The final body weight of larvae increased with increasing nematode density. The body weight of larvae fed 100 nematodes ml^?1 did not differ significantly from that of larvae given Artemia nauplii. Results show that bighead carp larvae should be fed 100 free‐living nematodes per ml at each feeding time.     

Egg cannibalism by ladybird larvae is less frequent than expected from the nutritional benefit accrued to cannibals

Egg cannibalism is a widespread phenomenon in predatory arthropods. However, conflicting results have been reported regarding the nutritional value of conspecific eggs. Therefore, evaluation of the value of a mixed diet of conspecific eggs and aphids for survival and growth of Adalia bipunctata (Coccinellidae) larvae was tested. Subsequently, the propensity for cannibalism of naive and experienced larvae was assessed in two experiments in which the relative density and quality of conspecific eggs were manipulated in an experimental arena. It was found that larvae that were fed a mixed diet of conspecific eggs and aphids moulted into larger adults than those fed either aphids or eggs, and those that fed on conspecific eggs lost less mass than those fed only aphids during pupal stage. Additionally, in an experimental arena, attacks on aphids were more frequent than expected when conspecific eggs occupied 50% and 75% of the patches. When 50% of patches were occupied by conspecific eggs, the preference for aphids was less marked when larvae had previously experienced cannibalism (76% vs. 52% respectively) or when offered in the arena conspecific egg the cuticular hydrocarbons of which had been removed (76% vs. 48%, respectively). However, cannibalism was not enhanced if larvae experienced heterospecific prey shortages, but were supplemented with an artificial diet. Given that prey choice in A. bipunctata larvae is driven by chemical cues and that hydrocarbons on the egg surfaces and in larval tracks are very similar, we hypothesize that the naive larvae avoid eggs because of the uncertainty that those hydrocarbons indicate either eggs or conspecific larvae.     

Suitability of monotypic and mixed diets for Anopheles hermsi larval development

The developmental time and survival to eclosion of Anopheles hermsi Barr & Guptavanij fed monotypic and mixed diets of ten food types were examined in laboratory studies. Larvae fed monotypic diets containing animal detritus (freeze‐dried rotifers, freeze‐dried Daphnia pulicaria, and TetraMin® fish food flakes) and the mixotrophic protistan Cryptomonas ovata developed faster and survived better than larvae that were fed other monotypic diets. Survival to adulthood of larvae fed several concentrations of the diatom Planothidium (=Achnanthes) lanceolatum was poor (<13%) and larval development time was approximately twice that of larvae fed TetraMin® fish food flakes, the standard laboratory diet. Larvae fed monotypic diets containing prokaryotes (bacteria [Bacillus cereus] and cyanobacteria [Oscillatoria prolifera]) and brewer's yeast (Saccharomyces cerevisiae) failed to survive beyond the 1^st and 2^nd instar, respectively. Larvae fed only chlorophytes, single‐celled Chlamydomonas reinhardtii and filamentous Spirogyra communis, failed to complete larval development, regardless of the concentration tested. Cohorts fed a combination of food types (mixed diets) usually developed better than cohorts fed monotypic diets. Food types that failed to support complete development when fed alone often facilitated development to adulthood when fed in combination with food types containing >1% C₂₀ polyunsaturated fatty acids as total fat, but regardless of essential fatty acid content, algae that produced mucilage and filaments that sank out of the feeding zone were poor quality diets.     

Evaluation of an improved RNA/DNA quantification method in a common carp (Cyprinus carpio Linnaeus 1758) larval feeding trial with Artemia,two nematodes (Panagrellus redivivus Linnaeus 1758, Panagrolaimus sp. Fuchs 1930) and dry feed

The RNA/DNA ratio commonly used as proxy for the nutritional condition of fish larvae is affected by RNA degradation during analysis. For evaluation of two strategies to improve RNA integrity, a three‐week feeding trial was carried out to assess the suitability of two nematode species (fam. Panagrolaimidae) as feed for newly hatched carp larvae (Cyprinus carpio) in comparison to Artemia nauplii (Artemia sp.) and a commercial dry feed. Aiming for an increased reproducibility of RNA/DNA determination, a high‐salt inactivation (RNA later) as well as a targeted approach with a recombinant RNase inhibitor were compared to the classical protocol using lab chip technology. Improved RNA integrity was observed with high‐salt inactivation when compared with a strategy applying a specific RNase inhibitor or the classic protocol. Carp larvae fed Artemia for 2 weeks and then dry feed for 1 week revealed the best overall growth performance as well as survival [83.0 ± 35.2 mg fresh weight (FW), 20.0 ± 2.4 mm total length (TL), 86.6 ± 11.7% survival]. Larvae fed the nematode species Panagrellus redivivus for 1 week and subsequently dry feed for 2 weeks (37.4 ± 29.1 mg FW, 14.7 ± 2.8 mm TL, 76.0 ± 6.0% survival) performed better than larvae fed with dry feed alone (28.2 ± 29.6 mg FW, 14.3 ± 2.9 mm TL, 54.3 ± 14.2% survival) or those receiving Panagrellus for 2 weeks. Between both nematode species, Panagrellus was a better feed with regard to growth performance and survival. RNA/DNA ratios ranged between 0.65 ± 0.27 (8 days post‐hatch) and 1.96 ± 0.63 (22 days post‐hatch) and were in the same treatment order as the other growth parameters. RNA/DNA ratios were significantly correlated with the growth rate, and decreasing RNA/DNA ratios in larger larvae may reflect decreasing growth rates with size rather than decreased nutritional status. Here, an improved RNA/DNA ratio protocol is presented in a feeding trial that reveals the suitability of nematodes as a first feed for common carp larvae.     

Growth response of African catfish,Clarias gariepinus (B.), larvae and fingerlings fed protease‐incorporated diets

African catfish, Clarias gariepinus (B.), is one of the promising freshwater fish species in African aquaculture but the expansion of its farming needs more production of its larvae. The use of live food organisms at first feeding for larvae is still obligatory. That increases the cost of larvae production. Hence, the incorporating of exogenous enzymes especially protease in artificial microdiets may provide affordable alternatives for enhancing the larvae performance. The present study was carried out to evaluate the growth and survival of larvae or fingerlings of African catfish fed artificial diets incorporated with different protease levels. Four artificial diets were formulated and enriched with protease enzyme at levels of 0.0, 750, 1,000, and 1,250 unit/kg diet; after that diets were made into crumbles (100–200 µm diameter). After absorption of the yolk sac, diets were offered to fish larvae (3.6 ± 0.2 mg) in triplicates as a starter feed up to apparent satiation every two hours for 30 days. In another treatment, fish larvae were fed on newly hatched Artemia nauplii (2,500 Artemia/L) as a starter food. In another experiment, African catfish fingerlings (10.1 ± 1.6 g) were fed on the same diets up to satiation twice a day for 2 months. It was noticed that the dietary protease improved larval growth and survival but not as Artemia nauplii did where fish larvae fed on Artemia nauplii showed highest growth and survival followed by those fed a diet enriched with 1,250 unit/kg diet of protease. The mortality of larvae fed protease‐enriched diets as well as the control diet was occurred mostly at the first week reaching its maximum at the third week. The poor growth was observed with fish larvae fed the control diet. Meanwhile, catfish fingerlings fed protease‐enriched diets showed higher growth over those fed the control diet. The larvae survival (11.0%–41.7%) was enhanced by increasing protease levels and it was lower than that of fingerlings (95.6%–100.0%). Furthermore, protein retention and digestibility were significantly improved with protease supplementation over the control diet especially at a level of 1,000 unit/kg diet. As compared with the previous studies, live food should be used in larvae rearing for the first week after that a starter diet enriched with protease at levels of 1,250 unit/kg diet should be used. In case of fish fingerlings, the dry diets should be enriched with 1,100 unit/kg diet to improve diet digestibility and subsequently enhance their growth.     

Effect of feed on larvae of Macrobrachium malcolmsonii (H. Milne Edwards) reared in synthetic brackishwater

Freshwater prawn, Macrobrachium malcolmsonii, has potential for aquaculture. Larvae of M. malcolmsonii were reared in synthetic brackishwater using commercial salts. Live and artificial feeds were provided to larvae either individually or in combination. Survival was significantly higher when larvae were fed with live feed only. However, larvae fed with artificial feed showed significantly lower survival. Survival was significantly higher when Artemia combined together with other feeds. Despite its limitations, synthetic brackishwater can be used for freshwater prawn seed production.     

Persistence of Trichinella spiralisin Rat Carcasses Experimentally Mixed in Different Feed

Trichinella spiralis infected rat carcasses were incubated for 6 weeks in several animal feeds to assess how long Trichinella can present a risk for an outbreak in contaminated feeds. In groups of 6, 24 infected target rats were placed in silage, grained barley, propionic acid-preserved feed, and also into simulated pasture conditions. Test environments were sampled after one-, 2-, 4-, and 6-week-incubations. Trichinella larvae were recovered by digestion, and their infectivity was evaluated in rats. A two-week incubation reduced the number of recovered larvae, but still after 6 weeks low numbers were isolated from all feeds except from the experimental group simulating pasture conditions. After 2 weeks storage, the larvae were infective in all storage environments. However, up to 4 weeks, they survived only in the propionic acid-fermented feed and there in small numbers with reduced reproductive capability. This indicates the possibility of farm animals to get infection from rats or other infected material being hazardously mixed with hay or other feed. If silage is stored for at least one month before use, however, the risk from this forage appears to be minimized.