Application of isotopic techniques to assess the nutritional performance of macroalgae in feeding regimes for shrimp

Due to their nutritional properties, several species of macroalgae have been used as dietary supplements for shrimps and other marine species. Since macroalgae represent a natural source of nutrients in the shrimp’s natural environment, attempts have been done to co-culture macroalgae and shrimps. The nutritional performance and digestibility of macroalgae-derived meals have been tested in formulated diets for shrimp. One of the aspects requiring further research is represented by the loss of nutritional properties occurring when the macroalgal biomass is dried out as compared when the algal biomass is ingested as live biomass. Several nutritional methodologies have been used to evaluate the performance of different ingredients used or proposed for aquaculture feeds. The use of stable isotopes as tools to assess nutritional contributions of specific ingredients to growth is one of many emerging nutritional techniques applied in aquaculture

Economically important marine larvae: Aquaculture production and larval rearing

The production of animals through aquaculture practices has narrowed down the dependence on fisheries-derived products. Aquaculture production yields are increasing but the majority of farmed aquatic animals are still represented by freshwater fish such as carp and tilapia. On the other hand, the production of marine organisms is dominated by several species of fish, crustaceans and molluscs; which have been successfully breed in captivity through their whole life cycles. These advances have been in part supported by applied research that has led to development of well-established rearing practices. The continued growth of the aquaculture industry requires high numbers of good quality postlarvae and juveniles produced in commercial hatcheries. Very often, the larval rearing of marine species represents the main bottleneck of the whole aquaculture production process and this is highlighted by the present situation with the production of marine fish. Although hundreds of species of marine fish are viable for farming, the current production accounts to only 3% of the global production of farmed aquatic animals. This figure is in part explained by the current lack of knowledge on the digestive physiology and nutrient requirements for most marine fish larvae. While mollusc larvae entirely depend on phytoplankton, most economically important species of marine crustaceans and fish are strongly dependent on zooplankton during the larval stage. The intrinsic difficulties in producing large amounts of specific live feeds to support the larval rearing of many marine species represents one of the main problems that marine farmers have to cope with. Therefore, intensive research on the ontogeny and physiology of the larval digestive tract is continuously conducted in order to have a better understanding of the larval digestive processes. New findings on the biology and physiology of marine larvae rapidly impacts technical production aspects such as the shape and size of the rearing vessels, the establishment of optimal larval rearing conditions and the larval feeding protocols used to supply live and inert feeds. New research findings assist nutritionists to formulate diets that can successfully replace live preys needed during the critical larval rearing stages. The present chapter reviews a number of aspects derived from the extremely high amount of marine larvae that the aquaculture industry currently requires, focusing on the research and methods that have allowed producing increasing numbers of larvae, in particular through studies on the digestive physiology of marine larvae. The demand for live feed to rear marine larvae is also addressed; situation that conveys several economic implications that will persist until effective replacement of larval live feed with inert diets is achieved. Special reference is done on methods applied to evaluate larval quality, larval diets and feeding protocols, to finally conclude with a look to future trends in scientific and technologic developments to rear marine larvae

Nutritional role of the natural productivity and formulated feed in semi-intensive shrimp farming as indicated by natural stable isotopes

The natural productivity of semi-intensively managed shrimp ponds is frequently represented by a high variety of trophic elements that continuously supply nutrients to the farmed organisms. As in the natural ecosystems, these dietary components exhibit differing isotopic signatures at natural abundance levels and since these natural communities belong to different trophic positions and isotopic values of organisms tend to increase with trophic level, the isotopic differences can be measured and used to infer on the transfer of nutrients, hence allowing establishing relationships between consuming organisms and their diets. Isotopic values can be measured and integrated in mass-balance mixing models in order to quantify the relative contribution of multiple nutritional sources to the growth of a specific organism. By applying such methodology, it has been possible to estimate the relative dietary contribution of several elements that belong either to the biota of the farming environment or that are part of formulated diets. Careful sampling methods and the isotopic analysis of these samples provide valuable information not only in terms of what the consumer organism has selected, captured and ingested, but also in terms of the proportions of assimilated nutrients in the consumers’ tissues. The present review highlights the nutritional relevance that the natural productivity of semi-intensively managed ponds and the supplied formulated feed represent for farmed shrimp. A synthesis of results from studies applying isotopic techniques to determine the relative contribution of dietary carbon and nitrogen derived from different biota elements and formulated feeds to the growth of shrimp is presented

Isótopos estables como trazadores nutricionales naturales en larvas y juveniles de Litopenaeus vannamei y Solea senegalensis

Los isótopos estables han sido ampliamente utilizados como marcadores nutricionales no-peligrosos para estimar flujos de nutrientes y energía en ecosistemas acuáticos. Los sistemas acuícolas son altamente viables para realizar evaluaciones isotópicas debido a que en su mayoría representan cadenas alimenticias cortas y controladas. El presente trabajo muestra una breve revisión de estudios que se han enfocado en utilizar las diferencias naturales en la composición isotópica de diversos ingredientes, dietas y organismos consumidores para determinar contribuciones nutricionales al crecimiento. Adicionalmente se presenta una serie de aplicaciones actuales en las cuales camarón blanco del Pacifico (L. vannamei) y lenguado de Senegal (S. senegalensis) fueron utilizados como organismos modelo. La contribución nutricional de harina de pescado y proteína de soya al crecimiento del camarón blanco fue evaluada al formular dietas con proporciones variables de nitrógeno suministrado por ambos ingredientes. Las contribuciones de nitrógeno al crecimiento fueron mayores a partir de la harina de pescado. En dos experimentos adicionales, se cuantificó la incorporación de carbono dietario proveniente de alimento vivo (Artemia) e inerte consumido por larvas y postlarvas de camarón y lenguado cultivados bajo diferentes regímenes de co-alimentación. Los aportes nutricionales provenientes del alimento vivo fueron mayores que los suministrados por el alimento inerte. La estimación de cambios isotópicos en tejido a diferentes tiempos permitió distinguir la dilución isotópica debida solo a crecimiento y la causada por las tasas metabólicas de recambio de nutrientes en tejido

Las técnicas isotópicas y sus recientes aplicaciones en las ciencias biológicas

Diversas técnicas analíticas han sido utilizadas en todas las disciplinas de la biología para generar un conocimiento más claro sobre algún fenómeno en particular. Un grupo de estas metodologías analíticas migró lentamente desde las ciencias geológicas hacia las ciencias biológicas. Tales metodologías están basadas en la determinación de las firmas isotópicas naturales presentes en diversos tipos de materiales, tanto inorgánicos como orgánicos. La mayoría de los elementos químicos que conforman la materia están presentes como dos o más isótopos. La única diferencia entre un isótopo de un mismo elemento y otro, es el número de neutrones, lo cual le otorga una masa ligeramente diferente a cada isótopo. Los isótopos estables han sido ampliamente utilizados como marcadores nutricionales no-peligrosos para estimar la forma en la cual nutrientes y energía son movilizados en los ecosistemas. De igual forma, las técnicas pueden usarse para determinar las rutas migratorias de varias especies y más recientemente han sido de gran utilidad en estudios nutricionales enfocados a evaluar nuevos ingredientes. La ciencia forense de los alimentos también ha utilizado técnicas isotópicas para detectar productos adulterados o falsos. El presente manuscrito muestra una breve revisión de las aplicaciones de los isótopos estables en diversas disciplinas de la biología, enfatizando aquellas áreas en las cuales existe un incremento importante de generación de conocimiento basado en estas técnicas

Digestive enzyme activity and food ingesta in juvenile shrimp Litopenaeus vannamei (Boone, 1931) as a function of body weight

A study was conducted to evaluate variations of digestive enzyme activities in Litopenaeus vannamei (Boone) reared in commercial ponds under semi-intensive conditions. Shrimp were collected at each body weight increase of 2 g. As the shrimp grew (2^12 g), signi¢cant increases in the activities of lipase and chymotrypsinwere observed. The total protease activity decreased from 6 g onwards. Trypsin activity showed a peak at 6 g and amylase activity increased two-fold after 2 g. Additionally, the stomach contents were analysed microscopically for shrimp between 2 and 10 g. Plant matter contributed above 30% of the total stomach content in 6-, 8- and 10-g shrimp. Detritus represented 58% and 62% of the total stomach content in 2- and 4-g shrimp, respectively, decreasing to 33^43% at greater shrimp weights. Arti¢cial feed showed amaximumcontribution of 20% in 6-g shrimp. The present results show changes in the enzyme activity after the shrimp reach 6 g in body weight, evidenced by a decrease in total protease and an increase in lipase and amylase activities. The amylase/protease ratio was 2.6 in 2-g shrimp and increased steadily to 9.6 in 12-g shrimp. These ¢ndings suggest an adaptation of the enzymatic activity to diets with lower protein content as body weight increases, and may be related to the variation of the di¡erent items found in the stomach

Naturally-occurring stable isotopes as direct measures of larval feeding efficiency, nutrient incorporation and turnover

environmental conditions on stable isotope incorporation will be of broad relevance not only in terms of larval nutrition but can also more broadly inform the design and interpretation of ecological studies

Nutritional contribution of torula yeast and fish meal to the growth of shrimp Litopenaeus vannamei as indicated by natural nitrogen stable isotopes

Torula yeast (Candida utilis) and fish meal were used to formulate six experimental diets for Pacific white shrimp Litopenaeus vannamei. The dietary nitrogen supplied by fish meal was replaced by increasing dietary proportions of torula yeast (0, 7.5, 15, 30, 60 and 100%). Nitrogen stable isotope values (δ15N) were measured in ingredients, diets and muscle tissue of experimental animals in order to estimate the relative contributions of dietary nitrogen and dry matter supplied by both ingredients. At the end of a 29 d bioassay, there were no significant differences in survival rate among treatments. Shrimps fed on all diets containing torula yeast and fish meal had higher growth rates (k = 0.059-0.064) than animals fed on diets containing only fish meal or only torula yeast (k = 0.041-0.054). Incorporation of δ15N values of ingredients and muscle tissue into an isotopic mixing model indicated that the relative incorporation of dietary nitrogen and total dry matter from torula yeast to growth consistently increased in relation to increasing proportions of this ingredient in the experimental diets. The only exception was the diet formulated with the highest yeast content (60%, diet 40F/60T) where fish meal contributed a higher proportion of dietary nitrogen to growth. Dietary nitrogen from torula yeast available in diets 93F/7T, 85F/15T, 70F/30T and 40F/60T was incorporated in muscle tissue at proportions of 6.5, 13.7, 27.1 and 50.5 %, respectively. Estimated nitrogen residency time in tissue (t50) was relatively shorter in shrimps fed on diets 85F/15T and 70F/30T (3 d), indicating higher metabolic turnover rates in these animals than those fed on diet containing only fish meal. Growth and survival rates were statistically similar in shrimp fed on all mixed diets, therefore indicating the suitability of this single cell protein as dietary ingredient in diets containing up to 60% of torula yeast

Simultaneous estimation of the nutritional contribution of fish meal, soy protein isolate and corn gluten to the growth of Pacific white shrimp (Litopenaeus vannamei) using dual stable isotope analysis

The nutritional contribution of the dietary nitrogen, carbon and total dry matter supplied by fish meal (FM), soy protein isolate (SP) and corn gluten (CG) to the growth of Pacific white shrimp Litopenaeus vannamei was assessed by means of isotopic analyses. As SP and CG are ingredients derived from plants having different photosynthetic pathways which imprint specific carbon isotope values to plant tissues, their isotopic values were contrasting. FM is isotopically different to these plant meals in regards to both, carbon and nitrogen. Such natural isotopic differences were used to design experimental diets having contrasting isotopic signatures. Seven isoproteic (36% crude protein), isoenergetic (4.7 Kcal gr-1) diets were formulated; three diets consisted in isotopic controls manufactured with only one main ingredient supplying dietary nitrogen and carbon: 100 % FM (diet 100F), 100% SP (diet 100S) and 100% CG (diet 100G). Four more diets were formulated with varying mixtures of these three ingredients, one included 33% of each ingredient on a dietary nitrogen basis (diet 33FSG) and the other three included a proportion 50:25:25 for each of the three ingredients (diets 50FSG, 50SGF and 50GFS). At the end of the bioassay there were no significant differences in growth rate in shrimps fed on the four mixed diets and diet 100F (k = 0.215-0.224). Growth rates were significantly lower (k = 0.163-0.201) in shrimps grown on diets containing only plant meals. Carbon and nitrogen stable isotope values (δ13C and δ15N) were measured in experimental diets and shrimp muscle tissue and results were incorporated into a three-source, two-isotope mixing model. The relative contributions of dietary nitrogen, carbon and total dry matter from FM, SP and CG to growth were statistically similar to the proportions established in most of the diets after correcting for the apparent digestibility coefficients of the ingredients. Dietary nitrogen available in diet 33FSG was incorporated in muscle tissue at proportions representing 24, 35 and 41% of the respective ingredients. Diet 50GSF contributed significantly higher amounts of dietary nitrogen from CG than from FM. When the level of dietary nitrogen derived from FM was increased in diet 50FSG, nutrient contributions were more comparable to the available dietary proportions as there was an incorporation of 44, 29 and 27% from FM, SP and CG, respectively. Nutritional contributions from SP were very consistent to the dietary proportions established in the experimental diets

Incorporation of dietary nitrogen from fish meal and pea meal (Pisum sativum) in muscle tissue of Pacific white shrimp (Litopenaeus vannamei) fed low protein compound diets

Stable isotope analyses were applied to explore the relative dietary nitrogen contributions from fish meal and pea meal (Pisum sativum) to muscle tissue of Pacific white shrimp postlarvae (141 ± 31 mg) fed low protein diets having different proportions of both ingredients as the sole dietary protein sources. A negative control diet was formulated to contain 100% pea meal and six more isoproteic diets to have decreasing levels of pea meal-derived nitrogen: 95, 85, 70, 55, 40 and 0 % of the initial level. Growth rates were negatively correlated to dietary pea protein inclusion due to progressive essential amino acid deficiencies (sulfur amino acids, threonine, lysine, histidine). The nitrogen turnover rate significantly increased in muscle tissue of shrimps fed diets having high levels of pea meal; however, contrary to observations from a previous study using soy protein , the relative contributions of dietary nitrogen from pea meal to shrimp muscle tissue were equal or higher than expected contributions established by the dietary formulations. Results highlight the effectiveness of stable isotope analysis in assessing the nutritional contributions of alternative ingredients for aquaculture feeds and the potential suitability of pea as a source of protein (provided the diets are nutritionally balanced)