Takao Yoshimatsu

Use of Porphyra spheroplasts as feed additive for red sea bream

Two test diets with and without 5% Porphyra spheroplasts (PS) were formulated using white fishmeal as the main protein source. Red sea bream Pagrus major (mean body weight 15.4±0.1 g) were maintained in a flow-through system (100 L) of thermo-controlled sea water (salinity 32–34, 25°C, 8 L/min) with ordinary aeration (400–600 mL/min) under laboratory light conditions (light-dark 12 h:12 h). Fish were fed three times a day at 10:00, 14:00 and 18:00 hours by hand for 42 days at 6% body weight on each experimental diet. Studies revealed that growth performance, survival and nutrient retention were significantly (P<0.05) higher in the groups fed a diet containing spheroplasts (PS diet). Further, the fish fed the PS diet showed significantly (P<0.05) lower feed conversion rates. Both groups of the PS and control diets had similar levels of body nutritional profile in terms of proximate compositions and fatty acids without compromising blood serum related parameters. From these experimental results, thus, it is comprehensible that a supplementary diet containing Porphyra spheroplasts can be used for maximizing not only growth of P. major but also for utilization of the feed ingredients.

Supplemental effect of Porphyra spheroplasts on the growth and feed utilization of black sea bream

A 56-day feeding trial was conducted to evaluate the effects of Porphyra spheroplasts (PS) as a feed additive on growth, carcass composition and feed utilization of black sea bream. Four experimental diets with or without PS (0, 1, 3, 5% inclusion level) were formulated to determine the proper incorporation level for best growth and utilization using white fishmeal as the principal protein source. Three replicate groups of fish averaging 1.28±0.05 g (mean ± SD) were maintained in flow-through thermo-controlled sea water (32–34 psu, 25°C) aquaria (100 L) under the laboratory conditions (L12: D12) and fed three times a day at 09:00, 13:00 and 17:00 hours by hand at approximately 3% body weight on each diet. The rearing trial revealed that growth performance (in terms of weight gain, specific growth rate) are almost the same level in all the dietary groups, nevertheless the survival, nutrient utilizations and retentions (fee efficiency, protein efficiency ratio, protein retention rate, lipid retention rate) were significantly higher (P<0.05) in a group fed on the diet containing 3% spheroplasts. Further, the fish fed on the diet containing PS had significantly higher (P<0.05) crude lipid level in their dorsal muscles and viscera. The fish fed a PS-based diet showed higher level of eicosapentaenoic acid and docosahexaenoic acid (DHA) in viscera and DHA in dorsal muscles. The results obtained in this feeding trial suggest that the optimum dietary PS supplementation level up to 3% for black sea bream can be considered as improved consequence on growth performance, nutrient utilization or body composition were noticed.

Effect of dietary cobalt supplementation on the population growth of rotifer Brachionus rotundiformis

National Research Institute of Aquaculture, Fisheries Research Agency, Mie 516-0193, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Department of Biological and Environmental Chemistry, School of Humanity-Oriented Science and Engineering, Kinki University, Fukuoka 820-8555, Fukuoka Mariculture Corporation, Fukuoka 811-3512, Japan, and Institute of Aquaculture, University of the Philippines in the Visayas, Iloilo 5023, Philippines

Comparison between α‐LNA and DHA in early developmental stages of Takifugu obscurus and Takifugu rubripes

Rearing experiments were conducted to investigate the essential fatty acid requirements in the early developmental stages of river puffer Takifugu obscurus and tiger puffer T. rubripes using two n−3 series unsaturated fatty acids, α-linolenic acid (18∶3n−3, α-LNA) and docosahexaenoic acid (22∶6n−3, DHA), under salinity of 30 and 18.5–20.3°C. River and tiger puffer larvae used in this study were 15 and 14 days old after hatching, and their average body weights were 30.1 and 20.8 mg, respectively. The results on fatty acid requirements of these two species were evaluated from fish growth, survival, fatty acid composition of the fish body and activity test results. The DHA groups of both river and tiger puffer exhibited better survival and weight gain. However, there was no difference in the mean final body weights of river puffer between two dietary groups. Also, the DHA group of tiger puffer showed better results in the recovery test from anesthetic condition than that obtained in the LNA group. In an examination of the fatty acid compositions of the whole body, the LNA group containing no dietary DHA resulted in 0.5% DHA in tiger puffer and 1.1% DHA in river puffer. These results suggest that α-LNA from Artemia converted to eicosapentaenoic acid (20∶5n−3, EPA) and to DHA successively by their fatty acid metabolism. Symptoms following essential fatty acid deficiency were not observed in any experimental groups. As river puffer did not represent a significant difference in the dietary effects between α-LNA and DHA treatment groups, its essential fatty acid requirement was assumed to be somewhat closer to that of the freshwater fishes in comparison with that of marine fishes, including tiger puffer.