A. Sanz

Effects of dietary protein source on growth, feed conversion and energy utilization in rainbow trout, Oncorhynchus mykiss

Abstract Most alternative protein sources to fish meal contain other non-protein energy materials which may influence diet utilization. With the objective of making an overall evaluation of the energy utilization of fish feed ingredients, the following diets were studied: two control diets including either fish meal or casein as the sole protein source (FM and CA100, respectively) and three diets where 40% of the fish meal protein was substituted by one of the following sources: cottonseed meal (CO), lupin seed meal (LU) and corn gluten meal (CG). A sixth diet containing casein (CA40), which replaced 40% of the fish meal protein, was also included as an additional control in order to compare the protein ADC calculation using either fish meal protein or casein protein as reference proteins. All diets were made isocaloric (gross energy) and with the same proportion of estimated available macronutrients. Energy flow studies for dietary protein, fat and carbohydrate, together with an evaluation of the digestive utilization of these energy-yielding nutrients and their efficiency for feed conversion and growth showed that dietary energy efficiency was directly related to the digestible energy of the diets which was especially influenced by the dietary carbohydrate source. Fish adjusted their dietary energy intake to digestible energy levels in the diet. Lupin meal carbohydrate digestibility showed very low values compared to the other plant sources. Protein retention efficiency expressed as protein productive value showed values above 40% for all the experimental diets. Energy retention efficiencies as a function of intake, digestible and metabolizable energy are discussed.

Evaluation of lupin seed meal as an alternative protein source in feeding of rainbow trout (Salmo gairdneri)

Abstract The nutritive quality of trout diets including lupin seed meal at 10, 20, 30 and 40% of dietary protein content was evaluated. Influence of heating on nutritional quality was also tested. Food intake, conversion index, digestibility of dietary protein, protein efficiency ratio and protein productive value were the parameters evaluated. The possibility of including crude lupin seed meal in trout diets at levels as high as 30% of dietary protein was demonstrated. Heating did not improve nutritional quality.

Sunflower meal compared with soybean meals as partial substitutes for fish meal in rainbow trout (Oncorhynchus mykiss) diets: protein and energy utilization

Abstract This work evaluated the nutritive potential of sunflower meal protein as compared to soybean meal and fish meal protein in trout diets. Energy utilization was also studied to determine the overall nutritive value of the raw material. Sunflower meal protein could replace up to 40% of fish meal protein in the diet with results very similar to those obtained with soybean protein at the same replacement percentage. Sunflower meal showed good digestive utilization of protein, even though the digestible energy was low due to the carbohydrate fraction. The addition of an appropriate level of digestible carbohydrates to the diet made with this raw material improved the nutritive utilization of the dietary protein and of the diet as a whole.

Re-evaluation of crude fibre and acid-insoluble ash as inert markers, alternative to chromic oxide, in digestibility studies with rainbow trout (Oncorhynchus mykiss)

The validity of crude fibre and acid-insoluble ash as inert markers as alternatives for chromic oxide was tested for digestibility studies in rainbow trout. Six practical diets were assayed: one of fish meal (C), and five in which 40% of the fish meal protein was replaced by corn gluten meal (CGM), cottonseed meal (CSM), lupine seed meal (LSM), soybean meal (SBM) or sunflower meal (SFM) on a crude protein basis. The apparent digestibility coefficients for crude protein, NFE, dry matter and gross energy were calculated using crude fibre, acid-insoluble ash and Cr 2 O 3 as inert markers. For all diets, when acid-insoluble ash was used as the marker, results for the apparent digestibility coefficients for crude protein, NFE, dry matter and gross energy were higher (P < 0.05) than those based on Cr 2 O 3 . All apparent digestibility coefficients for the control, corn gluten meal, cottonseed meal and lupine seed meal diets calculated with crude fibre as the marker were similar to those based on Cr 2 O 3 , whereas all results based on crude fibre for the soybean meal and sunflower meal diets, compared with those obtained with chromic oxide, were lower (P < 0.05). Based on these results, if one considers chromic oxide as the reference marker, then acid-insoluble ash is not a suitable marker for digestibility studies in rainbow trout. With respect to crude fibre, our results suggests that this substance can be an effective endogenous marker, although attention should be paid to the type of crude fibre present in the diets.

Utilization of dietary protein by the eel (Anguilla anguilla): Optimum dietary protein levels

Abstract European eels, with mean initial body weight of 40 g and maintained at 25°C, were fed on diets of different protein content (35, 40, 45, 50 and 55% protein), for 60 days. Two fish-protein sources, white fish meal (WFM) and herring meal (HM), were separately tested at the stated protein levels. WFM was a better protein source than HM, for all the protein levels assayed, as observed by feed conversion, protein efficiency for growth and apparent digestibility. For both protein sources the optimal daily protein intake for maximum growth was about 1.4 g 100 g fish.

Utilization of dietary carbohydrates by fish: a comparative study in eel and trout

To evaluate the ability of the eel to use diets with high carbohydrate content, a comparative study was made by using the rainbow trout, a carnivorous fish, as a reference species. Four isoenergenetic diets (in terms of gross energy) were formulated incorporating different protein/carbohydrate ratios (450/200, 370/300, 290/400 and 210/500 as g/kg dry matter, respectively) and each one was tested in three replicates groups of eels and trout. The data on growth, food conversion and utilization of dietary protein and energy show that the eel has a comparatively greater ability than the rainbow trout for using diets with a high carbohydrate level. Thus it is postulated that higher carbohydrate levels could be used for formulating cheaper diets.

Utilization of different carbohydrates by the European eel (Anguilla anguilla)

Abstract The present study was conducted to compare the utilization of several different carbohydrate sources and to evaluate the effect of two different methods of feed-processing in eel feeding. Five experimental isoenergetic diets were formulated (all containing 28.5% protein, 8% fat and 40% carbohydrate in dry matter), differing in the carbohydrate source: raw wheat starch (RWS diet), corn malto-dextrins (MD diet), manioc ( Manihot dulcis ) meal (MAN diet) and pregelatinized corn starch (PCS1 diet). These four diets were manufactured by extrusion in a Clextral BC-45 extruder. A fifth diet was prepared with the same pregelatinized corn starch (PCS2 diet) but by using a customary laboratory procedure: pellets were made in a mincing machine after mixing dry premix with water and thereafter dried under hot-air flow. Each experimental diet was supplied to three lots of European eels. Feed acceptance, growth, feed efficiency, digestibility, dietary protein utilization, and effects on body composition were evaluated. All extruded diets were well utilized and promoted similar growth rates, irrespective of the origin and nature of the carbohydrate source. Diet PCS1 resulted in more tough pellets and was poorly accepted by the eels; besides its digestibility was clearly lower, so growth rate and feed conversion were the poorest. Results confirm the ability of eels to use high dietary carbohydrate levels and demonstrated the importance of selecting an appropriate processing method when these high carbohydrate levels are to be utilized.

Digestive enzyme activity of two stonefly species (Insecta, Plecoptera) and their feeding habits.

The digestive enzymes of two stoneflies species, Hemimelaena flaviventris and Isoperla morenica, were studied for the first time. These species are temporary water inhabitants and exhibit great feeding plasticity. Although they are traditionally referred to as predators, a previous study revealed that H. flaviventris incorporates some diatoms into its diet in addition to feeding usually on several prey, and I. morenica (in that study under the name of I. curtata) only feeds on animals occasionally. The enzymatic activities of digestive amylase, lipase, protease, trypsin and chymotrypsin were determined for each species at the same developmental stage. The results show that H. flaviventris has a greater digestive enzymatic pool and higher relative and absolute protease, lipase and trypsin activities than I. morenica. The latter has a relative higher amylase activity. As higher amylase activity is typical of phytophagous species and higher protease activity typical of carnivorous species; these results reveal that H. flaviventris is a more efficient zoophagous species than I. morenica. The ecological implications of these findings, including the higher secondary production of H. flaviventris in its habitat, are discussed.

Protein nutrition in fish: protein/energy ratio and alternative protein sources to fish meal.

Those interested in the design and manufacture of feeds for intensive fish farming face the basic concern of formulating mixtures for the best yield at the lowest costs. Of the macronutrients in the feed, protein has and continues to receive special consideration because fish present high and specific needs for this constituent. Traditionally, protein has been supplied primarily by fish meals. This paper presents a synthesis of the efforts made and the lines explored to achieve an effective reduction of the amount of fish meal in the feeds for fish, following two strategies: reduction of the protein in the feeds and the use of new raw materials to replace fish meal.ResumenLos interesados en el diseño y fabricación de piensos para el cultivo intensivo de peces han tenido como preocupación básica la confección de unas fórmulas que hicieran compatibles los mejores resultados de producción con los menores costes. De los macronutrientes constituyentes del pienso, ha sido y sigue siendo la proteína la que ha recibido una consideración especial debido a que los peces presentan unas necesidades altas y específicas de la misma. Dicha proteína ha sido aportada principalmente por las harinas de pescado. Este trabajo recoge una síntesis de los esfuerzos realizados y de las líneas que habría que explorar para conseguir una reducción efectiva de la cantidad de harina de pescado en los piensos para peces, utilizando dos estrategias: la reducción de la relación proteín/energía de los piensos y la utilización de nuevas materias primas reemplazantes de la harina de pescado.

Relationship between brain and liver oxidative state and maximum lifespan potential of different fish species.

The aim of the present study is to determine whether a relationship exists between the maximum lifespan potential (MLSP) of different fish species (Squalius pyrenaicus, Cyprinus carpio, Carassius auratus, Luciobarbus sclateri and Oncorhynchus mykiss) and the oxidative state of brain and liver. For this purpose, the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST) and DT-diaphorase (NAD(P)H:quinone oxidoreductase1) were measured together with the lipid peroxidation degree (malondialdehyde, MDA) in liver and brain tissues of the collected species. Only the brain tissue manifested a higher activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase in addition to a negative correlation between the values of MDA and MLSP among the different fish species. Hypotheses are proposed from the analysis of the obtained results that open new areas of research and converge on the importance of the theory of free radicals in the processes that condition the maximum life expectancy of an animal species.