M. de la Higuera

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.

Influence of handling and/or anaesthesia on stress response in rainbow trout. Effects on liver primary metabolism.

Abstract 1. 1. The overall effect of handling, anaesthesia and sham injection on some blood metabolites, liver glycogen and several key enzymes involved in liver carbohydrates and nitrogen metabolism was studied in rainbow trout. In addition, the possible role of anaesthesia (MS222) itself as a stress-inductor or suppressor was also studied. 2. 2. Stress resulted in hyperglycaemia and initially in liver glycogen depletion, as well as increasing plasma amino acid levels. 3. 3. Glycogen stores subsequently recovered while amino acid concentration fell. 4. 4. These changes seemed to correlate with the increased activity of liver fructose 1,6-bisphosphatase, glucose 6-phosphate dehydrogenase, alanine aminotransferase and glutamate dehydrogenase, thus supporting the hypothesis that gluconeogenic flux from amino acids increases in stressed trouts. 5. 5. Anaesthesia, under the same experimental conditions, did not seem to mediate in stress production, but rather resulted in stress suppression.

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.

Long-term effect of a high-protein/non-carbohydrate diet on the primary liver and kidney metabolism in rainbow trout (Salmo gairdneri)

Abstract Several aspects of the metabolic adaptation of trout liver and kidney to a high-protein diet were studied. Under this nutritional situation there were significant increases in the activities of the glycolytic enzymes phosphofructokinase (PFK) and pyruvate kinase (PK) from both tissues but with a different molecular basis. PFK activity was increased at subsaturating substrate concentrations, with a decrease in Michaelis constant (Km) values of about 70% in both tissues and without changes in the maximum velocity (Vmax). The activity of PK was increased all along the saturation curve, approximately 70% and 20% in liver and kidney respectively. However, no changes in the activities of glucose 6-phospate dehydrogenase (G6PDH) were detected. On the other hand, the activity of the gluconeogenic enzyme fructose 1,6-bisphosphatase (FBPase) from both tissues was increased only at cellular substrate concentrations. With respect to amino acid metabolism, liver alanine aminotransferase (AAT) was enhanced at all substrate concentrations, with a significant increase of almost 50% in the Vmax, without changes in the renal activity. Glutamate dehydrogenase (GDH) activity was almost 300% and 100% of control values, in liver and kidney respectively, observations which are in good agreement with the role of this enzyme in the two tissues.

Influence of the relative proportions of energy yielding nutrients on liver intermediary metabolism of the European eel

Abstract The influence of dietary protein, lipid and carbohydrate proportions on liver glutamate dehydrogenase (GDH), fructose 1,6-bisphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6PDH) and pyruvate kinase (PK) activities was investigated in the European eel (Anguilla anguilla). The highest weight-gain (%) and feed-efficiency indices were obtained using diets with the highest energy content and, for the same energetic content, those with the greatest carbohydrate level. GDH activity increased in fish fed diets with the highest protein: energy ratio with respect to diets either with lower protein or with higher total energy contents. FBPase showed an increased activity in the liver of fish fed on diets with the lowest carbohydrate content and the highest total lipids concentrations. G6PDH activity correlated positively with dietary carbohydrate concentrations and negatively with dietary lipids levels. The increase of carbohydrates and energy levels in the diet increased liver PK activity. In general terms, the European eel showed a certain capacity to adapt intermediary metabolism to changes in diet composition. Amino acid catabolism increased in response to a higher dietary protein: energy ratio. High carbohydrate levels enhanced glucose utilization to yield energy and lipid formation. Gluconeogenesis increased in response to a lower dietary carbohydrate content. High dietary lipid concentrations reduced gluconeogenesis and lipogenesis from carbohydrates.

The influence of high dietary fat levels on protein utilization by the trout, (Salmo gairdnerii)

Abstract 1. 1. The effect of total dietary energy content on protein utilization and on the levels of certain liver enzymes in trout was examined. Groups of trout or individual trout were fed a commercial diet to which different additional amounts of olive oil had been added. 2. 2. Fat digestibility was not affected by fat content in the diet. Dietary lipid levels did not affect protein digestibility. 3. 3. Indices of protein utilization improved markedly as dietary lipid level was increased. The effect was shown by an increase in biological value and a significant increase of protein productive value. 4. 4. Glutamate-pyruvate transaminase activity decreased and glucose-6-phosphatase activity increased when trout were fed a high lipid diet. 5. 5. The activities of other liver enzymes, (glutamate-oxaloacetate transaminase, lactic-dehydrogenase, glycerophosphate dehydrogenase and phosphoenolpyruvate carboxykinase) was neither increased nor decreased by dietary changes involving increases in fat level.

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.

Liver and white muscle protein turnover rates in the / European eel Anguilla anguilla: effects of dietary protein quality

Abstract The influence of the quality of dietary protein source on growth and protein synthesis and degradation rates was studied in the liver and white muscle of the European eel. Fish were fed isonitrogenous diets differing in protein source: one (control) contained fish meal, three others incorporating meat meal (MM) or sunflower meal (SFM) as the only protein source, and SFM supplemented with some essential amino acids (EAAs) were also tested. Fish fed diets containing unsupplemented MM or SFM exhibited dietary utilization and growth indices poorer than those fed the control, while EAA supplementation greatly improved the performance of the SFM-diet. Liver showed higher rates of protein synthesis ( k s ) and degradation ( k d ) associated with a higher capacity for protein synthesis per unit of DNA but a lower protein deposition efficiency (PDE), compared to muscle. Low quality dietary protein increased the protein turnover rate, with a higher protein synthesis rate per unit of DNA and RNA but a decrease of PDE. In white muscle, MM and unsupplemented SFM diets decreased k s without changing k d . The MM diet reduced the efficiency of protein synthesis and deposition. EAA supplementation of the SFM diet raised the protein synthesis rate and capacity as well as protein deposition compared to control values.