G. Cardenete

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.

Influence of temperature and dietary-protein supplementation either with free or coated lysine on the fractional protein-turnover rates in the white muscle of carp

The effect of protein quality and of supplementation of corn-glutenprotein with lysine on the growth, feed conversion and protein turnoverrates in white muscle was investigated in carp (Cyprinus carpio) acclimatedto either 18 or 25 °C. Fish fed the lysine-deficient diet showed asignificantly lower food intake, weight gain and feed-conversion efficiencythan animals fed the lysine-sufficient diets, regardless of environmentaltemperature. Coated lysine, compared with free lysine, proved to be asignificantly better way of supplementing dietary protein, as shown byfeed-conversion indices at 18 and 25 °C. White-muscle protein, RNA andDNA contents were not altered by dietary treatment or water temperature.Supplementation with coated lysine, but not with free lysine, significantlyincreased the protein-synthesis rate (KS) at 18 or 25 °Cin comparison to lysine deficiency, although not to control values. Theeffiiency of protein synthesis (KRNA) and retention (PRE)obtained for fish fed the coated-lysine diet, at 18 °C, reached controlvalues. At 25 °C PRE and protein accumulation rate (KG)showed the following significant differences: lysine-deficient diet <free-lysine supplemented diet < coated-lysine supplemented diet <control diet. Significant correlations were observed for Ks in relation withKD, KRNA or protein-related growth, at bothtemperatures.

Digestive enzymatic profile of Dentex dentex and response to different dietary formulations

Digestive physiology of on-growing common dentex (Dentex dentex), including protease, amylase and lipase activity in stomach, pyloric caeca, anterior and posterior intestine, was evaluated. The influence of dietary macronutrient balance on these digestive processes was also assessed. Four experimental diets with different protein:lipid:carbohydrate ratios (43/16/28; 43/24/4; 38/19/28 and 38/24/13) were formulated. The highest activity for acid proteases was located in the stomach at pH 1.5. Alkaline proteolytic activities showed the highest values in the pyloric caeca and posterior intestine at pH 8.5-9.0. Dentex showed substantial amylase activity in the pyloric caeca and posterior intestine. Lipase activity was higher in the pyloric caeca, anterior and posterior intestine and was not detected in the stomach. Feed composition influenced alkaline protease activity in the anterior and posterior intestine and was higher for the diet with less protein and more carbohydrates. Enhanced amylase activity was observed in the pyloric caeca and posterior intestine in those groups fed on higher carbohydrate and lower lipid level diets. High dietary carbohydrate levels produced the highest lipase activity but this only occurred in the anterior intestine. We can conclude that the digestive tract of dentex adapts well to protein digestion and possesses a high potential for digesting the other dietary macronutrients, too. Dietary carbohydrate content seems to induce changes in protease, amylase and lipase activity.

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.

Nutritive and metabolic utilization of proteins with high glutamic acid content by the rainbow trout (Oncorhynchus mykiss)

Abstract 1. 1. The use of high levels of vegetable proteins in trout feeding resulted in an increased specific GDH activity. Nevertheless, deamination ability was not as high as expected in relation to the level of glutamic acid, a major substrate of such an enzyme, existing in the utilized protein sources. 2. 2. Transaminase activities, GOT and GPT, showed no clear response to protein quality of the diets. In the case of GPT, lower values were measured when using corn gluten meal in diets, which is probably related to a very good nutritive utilization. 3. 3. The use of GDH and GOT as enzyme indicators of the utilization of dietary protein by the trout does not seem to be very useful due to their susceptibility of being influenced by quite different nutritional factors.

Effect of feeding method and protein source on Sparus aurata feeding patterns

The influence of dietary protein source (fishmeal, soy-protein concentrate and soy-protein concentrate supplemented with methionine) on voluntary feed intake, daily feeding rhythm and nutritive utilisation of diet was studied in the gilthead sea bream (Sparus aurata) fed by hand or demand feeding. Fish weighing 21 g were maintained indoors under natural conditions of temperature and photoperiod (transparent ceiling) and allowed ad libitum or self-feeding of experimental diets for 26 days, with three replicates per treatment. In the first experiment, the influence of hand or demand feeding on growth rate and feed utilisation of a fishmeal-based control diet was studied. In a second trial, involving different protein sources, fish were maintained under the experimental conditions for 6 days after 20 days training. The general composition of the experimental diets was: 45% protein, 14% lipids and 20% carbohydrates. Results showed that: (1) gilthead sea bream preferentially feed in the afternoon and evening; (2) demand feeding improved both food conversion and protein efficiency; (3) the protein source appeared to induce changes in the timing of feeding; and (4) supplements of methionine advanced the time of feeding and lengthened ingestion phases. D 2003 Elsevier Science B.V. All rights reserved.

Dietary Effect on the Proteome of the Common Octopus (Octopus vulgaris) Paralarvae

Nowadays, the common octopus (Octopus vulgaris) culture is hampered by massive mortalities occurring during early life-cycle stages (paralarvae). Despite the causes of the high paralarvae mortality are not yet well-defined and understood, the nutritional stress caused by inadequate diets is pointed out as one of the main factors. In this study, the effects of diet on paralarvae is analyzed through a proteomic approach, to search for novel biomarkers of nutritional stress. A total of 43 proteins showing differential expression in the different conditions studied have been identified. The analysis highlights proteins related with the carbohydrate metabolism: glyceraldehyde-3-phosphate-dedydrogenase (GAPDH), triosephosphate isomerase; other ways of energetic metabolism: NADP+-specific isocitrate dehydrogenase, arginine kinase; detoxification: glutathione-S-transferase (GST); stress: heat shock proteins (HSP70); structural constituent of eye lens: S-crystallin 3; and cytoskeleton: actin, actin-beta/gamma1, beta actin. These results allow defining characteristic proteomes of paralarvae depending on the diet; as well as the use of several of these proteins as novel biomarkers to evaluate their welfare linked to nutritional stress. Notably, the changes of proteins like S-crystallin 3, arginine kinase and NAD+ specific isocitrate dehydrogenase, may be related to fed vs. starving paralarvae, particularly in the first 4 days of development.

Nutritional and metabolic responses in common dentex (Dentex dentex) fed on different types and levels of carbohydrates.

The present study was aimed to evaluate the capacity of common dentex (Dentex dentex) to efficiently use dietary carbohydrates. So, the effects of different type and levels of carbohydrates on growth performance, feed utilization, fish composition, plasma metabolites and key metabolic pathways in liver and white muscle of common dentex are presented. Nine isonitrogenous (43%) and isoenergetic (22 MJ kg(-1)) diets were formulated combining three types, pregelatinized starch (PS), dextrin (Dx) and maltodextrin (Mx), and three levels (12, 18 and 24%) of carbohydrates. Growth performance was not significantly influenced by treatments. The best feed utilization was observed in 18% Mx group. Higher hepatic lipid content was found in fish fed lower dietary carbohydrate levels. PS induced higher liver and white muscle hexokinase and pyruvate kinase activities compared to the lower values observed for Mx. Malic enzyme and glucose 6-phosphate dehydrogenase in liver and white muscle were lower in Mx group. The influence of dietary carbohydrates source was more noticeable than those induced by the carbohydrate level, when glycolysis and lipogenesis pathways were considered. Common dentex is able to use properly dietary carbohydrates, although optimal dietary inclusion levels are below 24%. The greater protein-sparing effect was promoted by the less complex carbohydrate (maltodextrin) and the best feed utilization indices were obtained at intermediate levels of inclusion (18%).

Hepatectomy in rainbow trout (Salmo gairdneri). A preliminary study.

1. Partial hepatectomy (25% of liver mass removed) has been performed on rainbow trout using a procedure allowing a high level of survival. 2. The liver regeneration was complete from the point of view of liver weight, at the 30th post-operative day. 3. During the first weeks after surgery, the NH-excretion rate in both hepatectomized and shamoperated trout was higher than in intact controls. Likewise, the food intake was lower in the operated animals. 4. Both facts can be attribute to the stress situation caused by the surgical manipulations rather than the removal of the liver.