Shuichi Satoh

Trace minerals in fish nutrition

Abstract The role of trace elements in biological systems has been described in several animals. However, the knowledge in fish is mainly limited to iron, copper, manganese, zinc and selenium as components of body fluids, cofactors in enzymatic reactions, structural units of non-enzymatic macromolecules, etc. Investigations in fish are comparatively complicated as both dietary intake and waterborne mineral uptake have to be considered in determining the mineral budgets. The importance of trace minerals as essential ingredients in diets, although in small quantities, is also evident in fish.

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.

Common Carp, Cyprinus carpio

The common carp (Cyprinus carpio) belongs to the family Cyprinidae. In nature, carp live in the middle or lower reaches of a river with slow currents, or in marshes. Their habitats are usually weedy areas with a muddy bottom. Carp fry feed on zooplankton such as rotifers and copepods, but as they grow up they become benthic feeders, feeding on animals and other organic material. The cyprinids have been farmed since ancient times and today they are undoubtedly the most important teleost family cultivated on a global scale, the current production figure reaching over 13 million tons year−1. The common carp is an important culture species among the cyprinids, next only to silver carp and grass carp (Fig. 18.1), and its production has doubled over the last decade, reaching about 2.5 million tons in 1998, valued at US

Effect of supplemental phytate and/or tricalcium phosphate on weight gain, feed efficiency and zinc content in vertebrae of channel catfish

2.8 billion (Fig. 18.2). A large percentage of this is from the Asian region, particularly China. While production of common carp is widely practised, only about 3% of the cyprinids are cultivated in intensive systems (Tacon, 1993). Traditionally, carp are cultured in ponds or rice paddies, while advanced culture systems include irrigation ponds, running-water systems and net cages in lakes. The more organized culture techniques involve maintenance of breeders, fry production, yearling production and marketable fish production. The operations and feeding practices are outlined in Table 18.1. Relatively low-cost prepared diets are in vogue and little effort has been made to supply adequate amounts of nutrients from carefully selected ingredients, despite the existence of a great deal of scientific information.

Comparison of phosphorus retention efficiency between rainbow trout (Oncorhynchus mykiss) fed a commercial diet and a low fish meal based diet

Abstract A 12-week feeding experiment was conducted with fingerling channel catfish ( Ictalurus punctatus ) to determine the effect of supplemental phytate and/or tricalcium phosphate on weight gain, feed efficiency and zinc content in vertebrae. Catfish fed a diet containing 2.2% phytic acid had significantly reduced weight gain and feed efficiency (653 vs 853 and 0.90 vs 1.02, respectively) compared to fish fed a diet containing 1.1% phytic acid. Zinc content in vertebrae was significantly reduced from 132.7 to 59.1 μg/g as the level of supplemental phytic acid was increased from 0 to 2.2% in fish fed diets containing 50 mg zinc/kg diet. Vertebral zinc content was not reduced when phytic acid was supplemented to diets containing 150 mg zinc/kg diet. There was no effect of supplemental tricalcium phosphate on weight gain or zinc content in vertebrae.

Effects of organic acids on growth and phosphorus utilization in red sea bream Pagrus major

Aimed at developing environment-friendly aquatic feeds, a trial on rainbow trout to reduce phosphorus (P) loading is reported. Growth, feed quality performance, whole body P retention and the calculated P loading were compared between triplicate groups of fish reared with a commercial feed and an experimental diet formulated with low level of fish meal (FM, 20%) and low-P ingredients: defatted soybean meal (20%), corn gluten meal (25%) and blood meal (5%). The total P content was 18.1 and 9.9 g/kg, for the commercial and experimental diets, respectively. Fifty fish with an average weight of 1.9 g were allotted in tanks of 60 l and maintained at water temperature ranging between 12 and 20 °C. Fish were hand-fed twice a day to apparent satiety for 48 weeks. At the end of the trial, growth was comparable among fish from different treatments, although it was highest for commercial feed. Dietary treatments did not affect final specific growth rate (SGR), thermal-unit growth coefficient (TGC) or feed gain ratio (FCR). P retention levels were found to be significantly higher in the fish fed the experimental diet (35.9%) than those fed the commercial diet (18.5%). Moreover, P loading was much lower for this group than for fish fed the commercial feed (7.8 kg/ton of fish produced versus 17.3 kg/ton). The results indicate that practical low-P loading diets can be developed for rainbow trout through combinations of alternative protein sources. Furthermore, an optimal combination of diverse low-P protein sources could enhance the feed performance to a level comparable to conventional fish meal (FM) based diets.

マダイの産卵に対するイカミ-ルおよびオキアミ中の有効成分〔英文〕

A feeding experiment was conducted to investigate the effects of various organic acids and supplements on the growth, phosphorus (P) utilization, and environmental loading of nitrogen (N) and P in red sea bream Pagrus major. Seven diets designated as PA (0.5% inorganic P as Ca[H2PO4]2), PO (no inorganic P), CA (1% citric acid), MA (1% malic acid), LA (1% lactic acid), MHA (1% methionine hydroxy analog) and LTE (1% liquid trace elements) were formulated. Duplicate groups of 25 fish were fed four times daily to near satiation for 75 days. Fish fed CA and LTE diets showed significantly better weight gain and feed conversion ratio compared to fish fed diet PO. Absorption of P was significantly improved in all organic acid-supplemented groups compared to the PA and PO groups. The P retention in CA and LTE groups were significantly higher compared to PA and PO diets. The P excretion was also significantly decreased in all organic acid-supplemented groups. Thus, use of organic acids, in particular CA and LTE, in red sea bream diets can reduce the use of inorganic phosphorus and contribute to the development of much-desired eco-friendly diets.

Studies on the essential fatty acid requirement of channel catfish, Ictalurus punctatus

Red seabream broodstock were fed various diets of different nutritional quality for either 26 days or shortly before spawning to clarify the effective components in cuttlefish meal and raw krill which aid in quality egg production. The percentage of buoyant eggs was lowest in the control group receiving the white fish meal diet, and was elevated by the addition of 200mg DL-ƒ¿-tocopheryl acetate. The value was also effectively improved by replacement of white fish meal with defatted or intact cuttlefish meal as a protein source. Feeding broodstock with frozen raw krill after previously being fed control diet resulted in elevation of the percentage of buoyant eggs and normal larvae. Equally good results were obtained by substitution of cuttlefish liver oil in the control diet with 2.5% krill polar lipid or 2.5% krill nonpolar lipid. However, neither defatted krill meal nor fat-soluble fraction of cuttlefish meal showed the good effect on the egg quality. Consequently, the superior quality of cuttlefish meal to the white fish meal as a protein source for red seabream broodstock diets was reconfirmed. And the effective components in raw krill, aiding the reproduction of red seabream, are suggested to be the polar and nonpolar lipid fractions. In addition, vitamin E was also found to have the same efficiency for improvement of the egg quality.

Disease resistance and hypocholesterolemia in yellowtail Seriola quinqueradiata fed a non-fishmeal diet

Abstract Two experiments were conducted to characterize essential fatty acid deficiency in fingerling channel catfish and determine the qualitative requirement of channel catfish for essential fatty acids. Supplementation of 1% ethyl linoleate, 1% ethyl linolenate or 1% ethyl linoleate plus 1% ethyl linolenate to tristearin or ethyl oleate based diets (5% total lipid) did not improve the growth rate of catfish to the level obtained by feeding a 2.5% corn oil plus 2.5% cod liver oil diet during a 12-week study. Fish fed the lipid-free diet or the tristearin or ethyl oleate diets had a higher level of eicosatrienoic acid in their liver polar lipids. The growth rate of catfish was effectively improved by supplementation of 1% n−3 highly unsaturated fatty acids to a tristearin based diet (5% total lipid). These data do not indicate whether linoleic and/or linolenic acid are essential for the catfish; the n−3 highly unsaturated fatty acids appear to be responsible for the enhanced growth.

Nutritional studies in the seed production of fish-XXI. Effect of polar and nonpolar lipids from krill on quality of eggs of red seabream Pagrus major.

The physiology of yellowtail fed a non-fishmeal diet was examined, with a specific interest in the role of taurine in disease resistance and cholesterol metabolism. Decrease of disease resistance in fish fed a non-fishmeal diet was confirmed by mortality due to natural infection with pseudotuberculosis and artificial infection with Lactococcus garvieae. It is suggested that the most important symptoms related to decrease of disease resistance in fish fed a non-fishmeal diet is anemia. Anemia was improved by supple mentation with taurine. Significant elevation of relative expression of HMG-CoA reductase mRNA in fish fed a non-fishmeal diet suggests that cholesterol synthesis would be activated and not dysfunctional. Plasma cholesterol of these fish was elevated to the levels of control fish by supplementation of both cholesterol and taurine. These results suggest that hypocholesterolemia observed in fish fed a non-fishmeal diet compared with a fishmeal diet would be caused by insufficient dietary cholesterol and decrease of endogenous cholesterol due to the lack of dietary taurine.