Studies on the comparative efficiency of utilization of gross energy from some carbohydrates, proteins and fats by rainbow trout (Salmo gairdneri, R.)

By means of a comparative slaughter technique, energy balances were determined in growing rainbow trout. Seven parts of a fish meal/casein basal mixture were blended with either 1.3 parts sunflower oil or 3 parts of one of the following compounds: glucose, sucrose, lactose, gelatinized maize starch or gelatine. Each of these mixtures was pelleted with an adequate amount of the basal mixture. Equivalent amounts of the mixtures, containing one of the carbohydrates or gelatine, and the basal mixture were fed to duplicate tanks containing 11 trout of 15 g initial live weight. In addition, the mixture containing sunflower oil was fed at 83% and the basal mixture at 70% of this amount to duplicate tanks. The trials lasted for 46 and 47 days. Thirty-one to 46% of dietary gross energy, and 21–38% of dietary nitrogen were retained. Efficiencies of utilization of gross energy can be calculated from the differences in the results between each supplemented group and the group fed the basal mixture at the low level for the following supplements: lactose 11.0%, gelatine 19.4%, fish meal/casein 43.1%, glucose 57.4%, gelatinized starch 61.2%, sunjlower oil 63.2%, sucrose 63.5%. With the exception of sunflower oil, all supplements caused increased concentrations of ether extract and N-free extract in trout livers.     

The utilization of clam waste meal as a protein source for rainbow trout Salmo gairdneri

Solid waste recovered from clam processing wash water was evaluated for its utilization as a replacement protein for fish meal. Three diets, diets 1 and 2 formulated to simulate the Oregon Moist Pellet (OMP) and diet 3 (Rangen), were fed to rainbow trout (Salmo gairdneri) for eight weeks. The effects of the clam waste meal on fish growth, food conversion, carcass composition and whole body fatty acid content were determined. The clam waste diet supported maximum growth and food conversion. Carcass analysis of moisture, protein and lipid contents were similar among the moist feeds. The dietary levels of 20:5w3 + 22:6w3 and total polyunsaturated fatty acids (PUFAs) were significantly higher in the clam waste diet pellet.     

Role of dietary ascorbic acid in vitellogenesis in rainbow trout (Salmo gairdneri)

Adult rainbow trout which were fed a diet devoid of ascorbic acid for 21 months, including the stages of gonadal development, showed no macroscopic signs of avitaminosis C and no increased mortality compared to a control group of fish with dietary supplementation of this vitamin. Fish without dietary supplementation of ascorbic acid contained more lipid in the liver and less in the ovaries than the reference fish. The lipid metabolism of the maturing fish is thus affected when the dietary intake of ascorbic acid is very low or absent. Fish without dietary ascorbic acid became anaemic (reduced levels of haemoglobin and haematocrit) towards the end of the feeding period. The serum levels of oestradiol-17β and vitellogenin were also lower in these fish. Possible modes of action of ascorbic acid in maturing rainbow trout are discussed on the basis of the presented analytical data on ascorbic acid, gross composition, blood serum levels of oestradiol-17β, vitellogenin, total protein, albumin, cholesterol, calcium, phosphorus and haematological parameters.     

Studies on the utilization by rainbow trout (Salmo gairdneri Rich.) of feed mixtures containing soya bean meal and an addition of amino acids

This paper deals with the growth of fish and utilization of feed mixtures in which fish meal is partly substituted by powdered soya beans. In order to improve the quality of protein in the feeds, they were enriched with synthetic amino acids. The food coefficients of the feeds were calculated, as were the protein efficiency ratio and apparent net protein utilization, by chemical analysis.

The results of the experiment showed that an addition of amino acids improved the utilization of feeds. It was found that rainbow trout can utilize soya bean protein enriched with cystine (1%) and tryptophan (0.5%) almost as well as protein from the fish meal.

Chemical composition of the experimental fish is discussed, as well as the amino acid composition of fish muscles and selected physiological parameters: haematocrit, haemoglobin content in the fish blood, the hepasomato index, and the content of protein, amino-transferases and cholesterol in the fish blood serum.     

The effect of phytates on the growth of rainbow trout (Salmo gairdneri) fed purified diets containing varying quantities of calcium and magnesium

Rainbow trout were fed for 150 days on four purified diets containing 0 and 0.5% phytic acid. These diets contained increasing increments of Ca (0.92–1.30%) and Mg (0.054–0.085%). The fish fed the diets containing phytic acid had 10% reduced growth and feed conversion. Increasing Ca and Mg content of the diet in the presence of phytic acid did not affect growth and feed conversion. Fish fed diets containing over 1% Ca without phytic acid had a 5% reduction in growth and feed conversion. The zinc and iron levels in the blood of the fish fed the diets containing phytic acid were not significantly different from the controls. The copper levels in the blood decreased in the fish diets with increasing increments of Ca ang Mg, but phytic acid did not influence this change. Increasing increments of Ca and Mg reduced the mean copper levels in the liver from 60 to 37 ppm. Similar reductions were found when phytic acid was included in the diet. Mean liver zinc levels did not significantly vary regardless of the diet fed. In vitro tests confirmed that phytic acid/protein (casein) complexes are only partially hydrolyzed by pepsin. In vivo tests with rainbow trout in which a casein/phytate complex was substituted for casein showed a 6.6% reduction in diet digestibility. It was concluded that the reduced growth in fish fed diets containing phytic acid was related to a reduction in protein availability rather than to an alteration in the bioavailability of Zn, Fe, or Cu.     

Fertility of rainbow trout (Salmo gairdneri) gametes: Gamete viability in artificial media

A series of experiments was performed to test the effect of potassium ions (K⁺) on the storage of rainbow trout (Salmo gairdneri) sperm cells and eggs. Storage of eggs for up to 10 min in saline solutions, extender with K⁺ concentrations of ≤3.4 mM and coelomic fluid did not affect fertility. Fish Extender #6 had a detrimental effect on eggs within 15 s of application and reduced fertility to near zero within 10 min. Variation in the K⁺ concentration indicated that high (≥6.8 mM) concentrations decreased egg fertility while low (≤3.4 mM) concentrations had no effect on fertility. Insemination of eggs before the addition of Fish Extender #6 allowed storage for 14 h. Semen diluted (1:10) in coelomic fluid maintained fertility for 45 s, whereas semen diluted (1:1) in coelomic fluid maintained fertility for 60 min. Fish Extender #6 at K⁺ concentrations between 0 mM and 68 mM had no effect on fertility of semen diluted 1:2.5 after 1 h of storage.     

The vitamin E requirement of rainbow trout (Salmo gairdneri) given diets containing polyunsaturated fatty acids derived from fish oil

Groups of rainbow trout (mean initial weight 14 g) were given diets containing 10% of fatty acids derived from a white fish offal oil together with graded levels of vitamin E (2–10 mg/100 g) for 16 weeks. Fish increased in weight by eight-fold over the course of the experiment but there were no differences in weight gain between treatments, food conversion was similar in all treatments, no pathologies were observed and few mortalities occurred. In trout given the lowest dietary vitamin E intake, tissue levels of vitamin E were lowest in skeletal muscle, concentrations in most other soft tissues were about threefold that in muscle but higher levels were found in brain. Increased erythrocyte fragility occurred in those fish given diets low in vitamin E, and ascorbic acid-Fe³⁺-stimulated lipid peroxidation in liver microsomes decreased with increasing dietary vitamin E. Little or no malonaldehyde was formed in microsomes from trout fed diets containing 5 mg vitamin E/100 g or more. This was taken to be an adequate or safe concentration under the dietary conditions employed. Microsomes prepared from the muscle of trout given low levels (2 mg/100 g diet) of vitamin E were more susceptible to peroxidation in vitro than those obtained from gill, heart or liver. Microsomal susceptibility to peroxidation is determined by the ratio of vitamin E: peroxidizable unsaturated fatty acids in the microsomal membrane. Some of these ratios were measured and the results are discussed.     

Time pattern analysis of swimming activity and heart rate under the influence of chloramphenicol in carp (Cyprinus carpio L.) and rainbow trout (Salmo gairdneri R.)

In industrial fish production there is little information available about the effect of antibiotics on the fish organism. The swimming activity of carp and trout before, during and after treatment with chloramphenicol was observed. Due to the daily rhythmical organization of body function and closely correlated periods of activity and rest, a treatment with chloramphenicol at different times of the day has different effects on swimming activity. A significant increase in heart rate after treatment with chloramphenicol was detected as compared to the controls. These results suggest that treatment with chloramphenicol should be given during the last feeding.     

Effects of dietary copper and copper: Zinc ratio on rainbow trout Salmo gairdneri

Purified diets with 15 and 150 mg supplemental copper/kg with dietary copper: zinc ratios of 1:1 and 1:4 were fed for 20 weeks to rainbow trout of mean initial weight 15 g. No gross pathologies were noted in any group of fish; growth and feed conversion were the same in all groups of trout. Plasma zinc levels were positively correlated with dietary zinc intake but dietary copper level had no effect on plasma copper. Hepatic levels of copper and zinc were also related to the dietary intake of the respective minerals. The dietary copper: zinc ratio caused some small changes in the plasma and hepatic levels of a few minerals, but no evidence was found to suggest any zinc—copper antagonism in rainbow trout. The activity of the copper, zinc metalloenzyme superoxide dismutase in liver was unaffected by dietary copper or zinc intake.     

Effect of hypervitaminosis a on the development of ascorbic acid deficiency in underyearling rainbow trout (Salmo gairdneri R.)

The effect of hypervitaminosis A on the development of ascorbic acid deficiency was investigated in rainbow trout reared on a practical diet. Excess vitamin A (124 000 I.U./kg) in the diet, as retinyl-palmitate, did not appear to interact with ascorbic acid metabolism of the trout. This dietary level of vitamin A did not affect the occurrence of the ascorbic acid deficiency symptoms, lordosis and scoliosis. Vitamin A does not appear to be toxic to rainbow trout at the level of 124 000 I.U./kg of diet and it would appear that the development of lordosis and scoliosis was due in this case to ascorbic acid deficiency.     

Influence of acclimation temperature on the osmotic regulation and survival of rainbow trout (Salmo gairdneri) rapidly transferred from fresh water to sea water

Certain physiological responses of two groups of rainbow trout acclimated at 10 and 17°C to a sudden change in salinity were investigated in order to determine the most appropriate temperature for direct transfer in salt water. Plasma osmolarities of fish acclimated at 17°C increased at a much faster rate following transfer and approached a much higher value than that reached by the fish acclimated at 10°C. The same was apparent for body tissue dehydration. Haematocrit values, the number of red blood cells, as well as red cell volume showed no significant difference between the two groups of fish for most of the experimental period. The larger increases in plasma osmotic pressure and tissue dehydration observed at 17°C are discussed in connection with the physiological adjustments accompanying higher temperature acclimation.     

Effect of Geotrichum candidum protein substitution in pelleted fish feed on the growth of rainbow trout (Salmo gairdneri Rich.) and on utilization of the diet

Three experiments were conducted with rainbow trout to determine if Geotrichum candidum GC single cell protein could replace 100, 75 or 50% of fish meal in a pelleted diet. When the fish meal was completely replaced by GC the fish growth was retarded after 3 weeks of the experiment. With the larger fish (individual weight 47–54 g) in the short trial there were significant differences between fish fed the control diet (fish meal) and those fed the 75% substitution of GC diet. The most remarkable differences in fish growth appeared in a 42-day trial with small fish (5 g individual weight) when fish groups fed diets with 0.50 and 75% replacement gave significantly different results (P < 0.05), being 93,9, 46.6 and 34.2% gain, with feed coefficients of 1.49, 2.77 and 3.67, respectively. With large fish fed diets with 0,50 and 75% GC replacement, apparent digestibility of protein was 64.7, 68.2 and 37.5%, but fat digestibility was 79.5, 91.1 and 81.0%, respectively. No significant differences in amounts of free plasma amino acid (PAA) were found between rainbow trout fed diets with 0 or 50% substitution, but there was a marked decrease in PAA in the group fed the diet with 75% GC substitution. Analysis of chosen heavy metals was made on diets, fish and faeces, and Cu in particular was found not to be accumulated in the fish body.     

Incorporation of potato protein concentrate in diets for rainbow trout: effect on feed intake, growth and feed utilization

Five isonitrogenous and isoenergetic diets were composed to investigate the effects of incorporation of potato protein concentrate (PPC) in the diet of rainbow trout, Oncorhynchus mykiss (Walbaum), on feeding rate, growth, feed utilization and body composition. The experimental diets contained 0, 22, 56, 89 and 111 g kg⁻¹ PPC, respectively. A 4-week trial was conducted at about 12°C. The results showed that with increased incorporation levels of PPC, feeding rate, growth and feed efficiency decreased significantly. Incorporation of PPC in the diets significantly decreased the dry matter content and fat content of fish body, while protein and ash contents increased.     

The effect of slaughtering procedures on blood spotting in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

Rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) were submitted for various slaughter and bleeding procedures to see what effect this would have on blood drainage of the muscles. Results show that the bleeding method is of less importance, while it is the timing that is important. No significant difference in bloodspotting was observed between fish that were bled live by a gill cut or percussive killed and bled by gutting. Most of the drainage of blood in the fish muscle seems to occur within the first hours postmortem, so rigor mortis is of little importance. The visual appearance of the fillet was influenced by number and size of the bloodstains. Colour measurements with Hunter L*, a*, b* did not reveal this. We conclude that a gill cut is not necessarily to obtain bleeding, so the industry can omit this phase and go directly to gutting.     

Comparative studies on body composition of rainbow trout (Salmo gairdneri R.) in relation to type of diet and growth rate

Three populations of rainbow trout (mean initial live weight 40 g) were fed experimentally under almost the same conditions for 49 weeks. The aim of the experiment was the examination of the changes in the relative proportions of the major whole body constituents (water, protein, fat and ash) in relation to type and amount of diet and growth rate. Two pelleted dry diets (A and B) and one mixed diet (C) were used. The amount of food given daily to the fish in the case of diets A and B was continuously based on fish body weight and water temperature. The population which received diet C (raw material and pelleted dry food) was fed on maximum ratio. Sampling was carried out approximately every two months. After 25 weeks, and besides the regular sampling, fish were sampled from each population and analyses were made on their fillets. The same analyses were also carried out. on fillets and whole body material on a sample of wild fish, of almost the same age, fed on a variety of food organisms in a stream near the experimental tanks. When the results are expressed in terms of dry weight, the analyses of whole body material showed that ash content remained fairly constant in all populations throughout the experimental time. Further, with increasing body weight and age the percentages of water and protein decreased and the percentage of fat content increased in all populations and especially in fish fed on diet C which appeared to have the maximum growth rate and final mean body weight. Similarly, fish fed on diet B, which showed the lowest growth rate and final mean body weight, had low changes in the major body constituents throughout the experimental period. The lowest and the most regular rate in the changes of these parameters appeared in fish fed on diet A which also had a sufficient growth rate and mean final body weight. Analyses of the fillets for the three different types of food used have different results. The analysed wild fish had the highest percentage of water content and, expressing the results in terms of dry weight, the highest percentage of ash and protein content, while they appeared to have the lowest percentage of fat content, on both whole body material and fillets.Since the three types of diets used in this experiment gave three different growth rates, as well as three different body compositions of the reared trout, it is suggested from the present results that the relative proportions and changes of the four body constituents and effects on the growth rate of trout are strongly affected by the type of food.     

Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.     

黄鳝生长差异基因发掘及其调控机制初步研究

该研究对体质量为 (25.03±0.02) g 的健康黄鳝 (Monopterus albus) 进行了10 周的养殖实验,探究了低鱼粉饲料中添加牛磺酸对黄鳝生长、消化率及肠道酶活性的影响。实验设置了高鱼粉组 (42%, FM)、低鱼粉组 (22%, T₀) 以及在低鱼粉饲料中分别添加0.2% (T_0.2) 和0.5% (T_0.5) 牛磺酸的4个处理组,每组5个重复。结果显示,与FM组相比,T₀组黄鳝的增重率、蛋白质效率、干物质消化率和蛋白质消化率显著下降 (P<0.05),饲料系数显著上升 (P<0.05)。添加适量牛磺酸可显著提高黄鳝的增重率、蛋白质效率和干物质消化率,降低饲料系数 (P<0.05),但T_0.5组黄鳝的增重率、蛋白质效率和饲料系数与T₀组相比无显著性差异 (P>0.05)。此外,T₀组肠道肌酸激酶 (CK)、钠钾ATP酶 (Na⁺-K⁺-ATPase)、碱性磷酸酶 (AKP)、胰蛋白酶 (TRYP) 和脂肪酶活性显著低于FM组 (P<0.05),T_0.2组的上述肠道酶活性均显著升高 (P<0.05),T_0.5组肠道Na⁺-K⁺-ATPase、AKP、TRYP和脂肪酶 (LPS) 活性虽高于T₀组,但无显著性差异 (P>0.05)。综上,低鱼粉饲料中添加0.2%牛磺酸可提高黄鳝的生长,改善肠道消化吸收功能,但添加过量牛磺酸 (0.5%) 效果不明显。     

Iron catalyzed oxidation of trout diets and its effect on the growth and physiological response of rainbow trout

Two experiments were conducted to determine 1) the effect of iron supplementation and the quality of fish oils on dietary lipid peroxidation and 2) the concurrent effects of diet rancidity and iron overload on the growth and physiological response of rainbow trout. Semi-purified diets supplemented with graded levels of iron (0–6250 mg/kg diet as ferrous sulphate) were fed to trout for 12–36 weeks. The malonaldehyde (MA) concentration of the test diets increased as the iron levels in the diets increased indicating that iron catalyzed lipid oxidation was occurring. However, when ethoxyquin was added to the oils, the increase in dietary MA level was significantly reduced. Fish oils with an initial high peroxide value were more susceptible to iron-catalyzed lipid oxidation. The concurrent effects of diet rancidity and iron overload (greater than 86 mg/kg) led to the development of unique histopathological signs, poor growth and high mortalities in the trout. In contrast, when diet rancidity was low (less than 10 µg MA/g diet), the toxic level of dietary iron was greater than 1380 mg/kg diet. The concentration of iron in trout tissues, and the hematocrit and hemoglobin concentrations increased as dietary iron levels increased and were not affected by the degree of diet rancidity.     

Studies on cryopreservation of eggs from rainbow trout (Salmo gairdneri) and coho salmon (Oncorhynchus kisutch)

The effect of pre-freezing treatments as well as freezing of inseminated, not water-activated eggs from rainbow trout Salmo gairdneri, and coho salmon, Oncorhynchus kisutch, was investigated in relation to survival and further development.Effects above freezing temperatures included: the temperature at insemination, viability of inseminated and unactivated eggs after storage, suitability of an incubation medium and the tolerance of eggs to various levels of the cryoprotectant dimethylsulfoxide (DMSO). Freezing experiments included: investigating the action of DMSO (0, 1, 2 mole) and the tolerance of coho eggs to temperatures between ?4.6 to ?30°C. Insemination temperatures between 0.5°C and 9.8°C (coho eggs) as well as incubation in an artifical medium (1-0°C) for 80 min (rainbow trout eggs) and 170 min (coho eggs) did not influence subsequent fertility. Storage of inseminated and unactivated rainbow trout eggs for 135 min and beyond reduced egg fertility. DMSO at 2 and 4 mole was detrimental to coho eggs (1-0°C). One mole DMSO had no (coho) or reduced (rainbow trout) influence on egg fertility when it was added gradually.In the presence of 1 mole DMSO most eggs remained unfrozen (67–89%) when kept for 10 min in frozen artificial medium (?4.6%) and 27–32% subsequently reached the eyed stage (control = 100). Further cooling (0.3°C/min) to ?10°C was still tolerated (62% unfrozen, 22% eyed eggs) but not to ?20°C (6% unfrozen, no development) and ?30°C (no survival). Use of 2 mole DMSO did not improve the results.     

Effects of dietary incorporation of potato protein concentrate and supplementation of methionine on growth and feed utilization of rainbow trout

Four diets (1, 2, 3 and 4) were formulated to contain different potato protein concentrate (PPC) levels (0, 22, 56, and 111 g kg⁻¹). Diet 5 contained 56 g kg⁻¹ PPC and 17 g kg⁻¹ methionine. A growth trial was conducted to investigate the effect on growth and feed utilization of incorporation of PPC and supplementation of methionine in the diet of rainbow trout. When the proportion of PPC exceeded 56 g kg⁻¹ the growth of fish decreased while both growth and feed utilization decreased when the dietary PPC was 111 g kg⁻¹. Protein productive value and condition factor of the fish decreased and mortality increased with the increase in the proportion of dietary PPC.