Influence of level and type of dietary protein, and of level of feeding on feed utilization by rainbow trout

Dietary valine improved growth, immunity, enzymatic activities and expression of TOR signaling cascade genes in rainbow trout, Oncorhynchus mykiss fingerlings

This study was conducted to determine the effects of dietary valine (Val) on growth, hemato-biochemical parameters, immunity, enzymatic activities, antioxidant status and expression of target of rapamycin (TOR) and 4E-BP genes in rainbow trout, Oncorhynchus mykiss (1.57 ± 0.03 g; 5.10 ± 0.34 cm). Six isonitrogenous (450 g kg⁻¹) and isoenergetic (20.90 kJ 100 g⁻¹_, gross energy) diets were designed to represent varied Val levels (10.5, 13.0, 15.5, 18.0, 20.5 and 23.0 g kg⁻¹ dry diet basis). Growth parameters improved significantly (P < 0.05) with the amelioration of dietary Val level up to 18.0 g kg⁻¹. Highest (P < 0.05) body protein content was noted at 18.0 g kg⁻¹ dietary Val. Significant differences in hematological, intestinal enzymatic activities and antioxidant parameters were noted. However, plasma variables did not show any significant differences except aspartate transaminase and uric acid. Total protein content increased significantly, while the albumin and globulin content did not show any significant (P > 0.05) difference. Moreover expression of TOR mRNA and elF4E-binding protein (4E-BP) was observed higher (P < 0.05) at 18.0 g kg⁻¹ Val. On the basis of results, optimum dietary Val requirement for maximal growth of rainbow trout was determined to be 18.19 g kg⁻¹ of dry diet, corresponding to 40.42 g kg⁻¹ of dietary protein.

Dynamics of plasma free amino acids in rainbow trout (Oncorhynchus mykiss under variety of dietary conditions

Plasma amino acid profiles in the systemic circulation of rainbow trout acclimated to diets containing different protein sources, with and without supplementation with free amino acids, were monitored for up to 120 hours after consumption of the diets. Plasma concentrations of lysine, methionine, and isoleucine increased more rapidly after feeding a diet supplemented with these amino acids in free form and, depending upon the increase in plasma concentration, remained at concentrations above those in fish fed the basal diet for at least 24h after feeding. Dietary supplementation with isoleucine increased plasma concentrations of leucine and valine as well as of isoleucine. Maximum plasma concentrations for most amino acids were attained between 12 and 24h postprandial. Dietary inclusion of gelatin caused more rapid elevations in plasma glycine and serine than did free glycine. Feeding at three hour intervals resulted in stable plasma concentrations of individual amino acids in contrast to the fluctuations occurring when fish were fed once daily. Frequent feeding favoured a higher proportion of protein to lipid in body composition.

The effect of dietary energy and protein concentration and feeding level on feed utilization and body composition of carp (Cyprinus carpio L.)

A three factorial designed feeding experiment with common carp (Cyprinus carpio L.) was carried out in an intensive experimental rearing system. Fish (initial body weight 200 g) were fed on two different levels of dietary energy (16 and 18 MJ DE/kg DM), two different levels of protein (320 and 420 g CP/kg DM) and also two different feeding intensities (100% and 75% of the maximum intake). The experiment was terminated when fish reached a mean body weight of 1300 g. Growth, feed utilization and nutrient composition of the whole body and fillet were observed. The highest growth was obtained when the fish were fed on the diet containing high dietary energy and high dietary protein with satiation feeding. High dietary energy, high dietary protein and restriction of feed intake improved feed conversion ratios. High dietary energy, low dietary protein and restrictive feeding increased energy utilization. Low dietary protein and restrictive feeding resulted in better protein utilization. Fish fed with high dietary energy contained more fat and less protein in their carcasses. A lower fat content but higher protein and higher ash content in fish carcasses was shown when fish were fed with a diet high in protein and fed restrictively.

The influence of the dietary carbohydrate: lipid ratio on the chronic toxicity of sodium pentachlorophenate to rainbow trout (Salmo gairdneri Richardson)

The influence of diets varying in carbohydrate: lipid ratio on the chronic toxicity of waterborne sodium pentachlorophenate (0 or 50 μg NaPCP.l(-1)) to rainbow trout (Salmo gairdneri) was examined over a 12 week period. The three diets used were practical salmonid formulations, equivalent in energy and protein content, with cerelose: fish oil ratios of 18.2∶4.7% (high carbohydrate, HC), 9.3∶9.1% (intermediate, INT), and 0.6∶13.8% (low carbohydrate, LC). With increasing levels of dietary carbohydrate trout exhibited enlarged livers, elevated liver glycogen content, reduced liver protein content, reduced body lipid content, reduced weight gain, and elevated feed: gain ratio. For all diet groups, exposure of trout to NaPCP resulted in reduced liver glycogen content, higher liver protein content, reduced levels of plasma total triiodo-L-thyronine and L-thyroxine, increased thyroid epithelial cell height, and increased feed: gain ratios relative to their respective dietary control group. NaPCP exposure led to nominal reductions in weight gain and body lipid content of fish reared on the HC and INT diets. NaPCP exposed fish on the LC diet gained significantly less weight but had a higher body lipid content than control fish. The increasing NaPCP bioconcentration factor (BCF) associated with increasing lipid content of fish (log BCF=2.75 [log % lipid] +0.30; r=0.95) may explain the differences in response. Correction of bioconcentration data for the lipid content of fish reduced the range in BCF from 5- to 2.8-fold.

Ontogenetical aspects of nutritional requirements in fish

Changes in morphology i.e. "metamorphosis", mode of respiration, allometric growth of organs, mode of swimming and efficiency of biochemical pathways are briefly reviewed. It is suggested that these processes form the basis for progressive changes in nutrient requirements involving formation and development of several organs, systems and function. Digestive tract morphology changes during ontogenesis and aspects of fish metabolism, protein synthesis rate and body growth rate are interconnected and an attempt is made to explain these processes so as to understand the specificity of larval and juvenile fish nutrient requirements as compared to subadults. Protein and amino acid requirements given the body mass perspective and the generalization of the protein maintenance requirement in protein requirements for maximum growth was estimated to amount to 5-20%. Several cases of amino acid deficiency symptoms showed strong dependence on fish weight (age), but even most numerous studies on salmonids are lacking complete research throughout the life history of one species in defined nutritional and environmental conditions. Larval and juvenile fish have reduced capacity of catabolic adaptability and this fact links them to strictly carnivorous mammals. An attempt is made, for the first time, to relate amino acid needs of fish to young and/or carnivorous mammals. Vitamin requirements of fish are reviewed, taking into account the relationship between body size and time of the first appearance of deficiency symptoms. These are virtually no studies on vitamin requirements in larval warm-water fishes and very few on first feeding salmonids. The same applies to the vitamin need in reproductory fish. Fatty acid deficiencies manifest themselves faster in juvenile fish, but larval fish might require separate classes of lipids, phosphatidylcholine, in the diet to develop and grow at all. It seems that the studies on nutrient requirements have so far not used an ontogenetical perspective, but evidence given throughout this work argues that it would be worthwhile.

Response of rainbow trout (Salmo gairdneri) to increased levels of available carbohydrate in practical trout diets

1. The physiological response of rainbow trout (Salmo gairdneri) reared on different levels of available carbohydrate in practical trout diets having the same levels of energy and nitrogen for 16-24 weeks was determined. 2. Weight gain was significantly reduced in trout reared on the highest level of available carbohydrate, 210 g cerelose (alpha-glucose) kg, and there was a significant linear regression (R2 0.88 of dietary carbohydrate on weight gain. 3. Liver: body-weight values and liver glycogen levels increased in relation to increased dietary carbohydrate. 4. Liver glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity increased and liver phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity decreased per kg body-weight of fish with increasing dietary carbohydrate. However, no significant effect was noted on the activity of these liver enzymes above a dietary cerelose level of 140 g/kg. 5. Liver fructose diphosphatase (EC 3.1.3.11) activity increased with increasing dietary carbohydrate has been interpreted as meaning a recycling of triosephosphate to glucose-6-phosphate. 6. Dietary carbohydrate level had no significant effect on the liver pyruvate kinase (EC 2.7.1.40) activity, the rate of glucose utilization or the percentage conversion of [14C]alanine to glucose in the plasma of trout. 7. The results indicate that rainbow trout have a limited ability to adapt to increased dietary carbohydrate and a level in excess of 140 g/kg of the diet is not efficiently utilized.

Effect of various triglycerides on blood and tissue cholesterol of calves

Blood and tissue cholesterol responses were measured in six groups of four calves each fed for 24 weeks reconstituted nonfat dry fat milk in which 30% of calories was derived from one of the following: soybean oil (SBO), beef tallow (T), medium-chain triglycerides (MCT), and 1:1 soybean-oil tallow (SBO/T) combination. Two groups of four calves each also were fed SBO-milk plus dry feed and T-milk plus dry feed, respectively. Blood cholesterol concentration was significantly greater in SBO-fed calves than in T-fed calves. Calves fed MCT-milk had significantly lower blood cholesterol than calves fed T- or SBO-milk. Significant differences in cholesterol concentration were noted for the liver, perianal fat, and for omental fat.