Efficacy of insect larval meal to replace fish meal in juvenile barramundi, Lates calcarifer reared in freshwater

The present experiment was conducted to evaluate the efficacy of dietary protein from black soldier fly, Hermetia illucens, larval meal (BSFL) to replace fish meal (FM) protein in juvenile barramundi, Lates calcarifer. Larvae of black soldier fly were fed with the underutilised crop, sesbania, Sesbania grandiflora. Five isonitrogenous (44% crude protein) and isocaloric (16.0 kJ available energy/g) experimental diets were formulated to replace FM using processed BSFL meal at 0 (control), 25% (BSFL25), 50% (BSFL50), 75% (BSFL75) and 100% (BSFL100). Data for proximate and amino acid analysis suggested BSFL meal as an inferior protein ingredient than FM, but parallel to soybean meal. At the end of 8 weeks of fish feeding trial, there were no significant differences in the average weight gain (WG) and specific growth rate among the group of fish-fed control, BSFL25 and BSFL50 diets (P < 0.05). Although numerical differences were recorded in the fish whole-body proximate composition, crude protein and moisture content were not much affected by the different dietary treatments. Essential amino acids including arginine, histidine, lysine and methionine were found to be higher in the whole body of fish-fed BSFL100 diet. Broken line regression analysis of average WG showed an optimum FM replacement level of 28.4% with BSFL meal. Therefore, the present experiment clearly demonstrates that the maximal dietary inclusion level of BSFL meal as FM protein replacer for the optimum growth of juvenile barramundi reared in freshwater could be greater than 28.4% but less than 50%, without any adverse effects on the fish whole-body proximate and amino acid composition

Dietary soybean meal on growth and intestinal morphology of South American catfish, Rhamdia quelen, larvae Farelo de soja em dietas para larvas de jundiá (Rhamdia quelen) sobre o crescimento e morfologia intestinal

The effects of the replacement of bread yeast by soybean meal in diets for Rhamdia quelen larvae on growth, survival, and intestinal morphology were analysed. Larvae were fed for 20 days with five diets: a control diet formulated with 57% of bread yeast, and other four diets in which soybean meal at concentrations of 14.25, 28.5, 42.75 and 57% was added to obtain 25, 50, 75 and 100% of bread yeast replacement. Growth and survival parameters were negatively affected by dietary soybean meal inclusion. Larvae fed control diet showed significantly higher mean weight, specific growth rate, final biomass, and survival rate than larvae from other treatments. Enterocyte height and fold width of the posterior intestine showed highest values in the control group, and an inverse linear relationship with the level of dietary soybean meal inclusion was observed, however, in the anterior intestine the morphology parameters were not affected by the diet. These results indicate that inclusion of soybean meal in diets for R. quelen larvae negatively affects growth and survival, as well as the capacity for digestion and absorption of nutrients, mainly in the posterior intestine.<br>Neste estudo, foi analisado o efeito da substituição de levedura de pão por farelo de soja em dietas para larvas de Rhamdia quelen no crescimento, sobrevivência e morfologia intestinal. As larvas foram alimentadas durante 20 dias com cinco dietas experimentais: uma dieta controle formulada com 57% de levedura de pão e quatro dietas em que o farelo de soja foi adicionado em 14,25, 28,5, 42,75 e 57% para obter 25, 50, 75 e 100% de substituição de levedura de pão. As variáveis de crescimento e sobrevivência foram negativamente afetadas pela inclusão da soja na dieta. As larvas alimentadas com a dieta controle apresentaram maior peso médio, taxa de crescimento específico, biomassa final e sobrevivência, diferindo significativamente dos demais tratamentos. A altura dos enterócitos e a largura das pregas no intestino posterior apresentaram valores mais elevados no grupo controle, enquanto nos demais tratamentos mostraram uma relação linear inversa com o nível de inclusão de farelo de soja na dieta. No entanto, no intestino anterior, os parâmetros morfológicos não foram afetados pela dieta. Esses resultados indicam que a inclusão de farelo de soja em dietas para larvas de R. quelen afeta negativamente o crescimento e sobrevivência, bem como a capacidade de digestão e absorção de nutrientes, principalmente no intestino posterior

Progress in larviculture of the Atlantic halibut <i>Hippoglossus hippoglossus</i>

The main goal of the project is to develop intensive industrial scale production systems for halibut fry. Halibut eggs were obtained from three brood stocks both by stripping and by natural spawning. Photoperiod manipulation is used to increase the spawning period, and spawning now takes place in the period February to June/July. The eggs are disinfected and incubated in up-stream conical tanks (8°C, darkness) and transferred to larval incubators after hatching. Two incubator-types are used; small glass bowls (3 liter), run stagnant or semi-stagnant, or large conical silos (0.7-15m³) run with continuous water flow (4-8°C, darkness). These different systems can be used to bring the yolk sac larvae of halibut up to the stage of first feeding. The yolk sac phase lasts for 35-50 days dependent of the temperature, and the larvae are very sensitive to physical conditions (light, temperature, water currents) and the environmental microbial community during this development stage. The survival averages 80% (for adequate groups) in small bowls and 50-70% in large flow-through silo incubators.Adjustment of the light conditions is presently among the main challenges in halibut first feeding. The larvae are positively attracted by all light qualities and dense schooling in the surface of the tank is a frequent observation. Such behaviour will result in extensive mortality in a matter of a week, and must in all events be avoided. Use of submerged light or strong sublight, which has been reduced to 30% intensity by appropriate filters, combined with algal addition to the fish tanks have yielded adequate behavioural response and in turn positive feeding results, but the mechanisms are not adequately understood so far.The rotifer Brachionus plicatilis and Artemia enriched by long chain omega3 fatty acids by use of emulsified lipid diets (Selco-type, Artemia Systems SA, Belgium) have been used as live feed for the halibut larvae. The rotifers are normally used during the first 10-15 days, but attempts have been made to use small Artemia instead of the rotifer. Larger on-grown Artemia has been used after 3-4 weeks of feeding. Addition of microalgae to the fish tanks enhance both growth rate and survival through the phase of the first feeding. The larvae increase their body weight by approximately 10% per day in the initial phase (13°C), provided that adequate diets are used. Weaning may be started beyond day 50 after the start of first feeding, and metamorphosis will occur at the same time. Survival up to 20% has been obtained so far