Addition of the red macroalgae Turkish Towel Chondracanthus exasperates and taurine improves the performance of alternative plant‐based feeds for juvenile sablefish Anoplopoma fimbria

Turkish Towel Chondracanthus exasperates and taurine were added to alternative plant‐based feeds for juvenile sablefish Anoplopoma fimbria to evaluate the effect of these ingredients, alone or combined, on fish growth, feed intake and efficiency, whole body nutrient composition, and liver histomorphology. Fish growth was significantly increased with the addition of taurine, and to a lesser extent, Turkish Towel to the experimental feeds. Feed efficiency and protein retention were significantly improved with the addition of taurine, but were unaffected by Turkish Towel addition. As expected, whole body taurine content was significantly affected by taurine addition. Increases in whole body lipid were observed with both taurine and Turkish Towel addition, with a significant interaction between the two factors. Liver histomorphology was generally normal; however, histopathologic changes were observed in some fish at the end of the experiment. The occurrence of hepatocellular nuclear pleomorphism and clear cell foci was less among fish that had received the Turkish Towel feeds. The addition of taurine had no effect on the number of fish with a histopathologic change. Overall, results from this study reaffirm taurine supplementation is beneficial to sablefish receiving plant‐based feeds and indicate Turkish Towel may be a promising feed ingredient for this species.     

Effects of feeding a fish meal‐free soy protein concentrate‐based diet on the growth performance and nutrient utilization of red sea bream (Pagrus major)

Two groups of red sea bream (average body weight 85 g) were fed to satiation fish meal (FM) or FM‐free soy protein concentrate (SPC)‐based diet (FM‐sat and SPC groups respectively). A third group (FM‐pair) was fed the same amount of FM as of SPC fed to SPC‐sat group for 6 weeks. Growth rate of SPC group was significantly slower than of FM‐sat and FM‐pair groups (p < 0.05). Feed conversion ratios of FM‐sat and FM‐pair groups were similar and were better than that of SPC group (p < 0.05). Visceral fat somatic index of SPC group was significantly lower than of the other groups (p < 0.05), while that of the latter two groups were similar. Plasma triglyceride of FM‐sat and FM‐pair groups was similar and lower than the level of SPC group (p < 0.05). Trypsin activity in hepatopancreas of SPC group was significantly lower than that of other groups (p < 0.05). We suggest a low growth of SPC group was not simply related to low‐feed intake. Feeding of a FM‐free SPC‐based diet may reduce lipid accumulation and consequently lead to low‐growth performance, in red sea bream.     

Effects of inorganic and organic dietary copper supplementation on growth performance and tissue composition for juvenile red drum (Sciaenops ocellatus L.)

A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO₄) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.     

Evaluation of rubber seed oil as lipid source in red tilapia (Oreochromis sp.) diet

Rubber seed oil has a high potency to be used as a new lipid source within red tilapia diet. However, the rubber seed oil contains antinutritional factor such as hydrogen cyanide (HCN). HCN is classified into heat‐labile; therefore, heating effectively reduces the HCN content. Based on this fact, this research evaluated the use of rubber seed oil with and without heating as lipid source in red tilapia diet. Four isonitrogenous and isocaloric diets were prepared as experimental diet. Each test diet contains different lipid sources such as crude palm oil + corn oil (CTRL), crude palm oil + rubber seed oil with heating (CPO:PRSO), 100% rubber seed oil with heating (PRSO) and 100% RSO without heating (URSO). In average, there were no significant differences (Tukey: p < .05) among test diet except diet with 100% rubber seed oil without heating. It concluded that 100% rubber seed with heating within test diet has no effect on growth, feed performance, blood profile, cholesterol plasma, body and liver glycogen, malondialdehyde (MDA) and the activity of superoxide dismutase (SOD).     

First report of Streptococcus iniae in red porgy (Pagrus pagrus, L.)

This work describes the first isolation of Streptococcus iniae in red porgy, Pagrus pagrus (L.), and the first European isolation of this pathogen in gilthead seabream, Sparus aurata (L.). In both farmed fish species, infection resulted in lethargy, anorexia, abnormal swimming, exophthalmia and sudden death, with mortality rates of over 25% in red porgy and 10% in gilthead seabream. Beta-haemolytic Gram-positive cocci, catalase negative and oxidase negative, were isolated in pure culture from internal organs. Conventional and rapid identification systems, and 16S rRNA gene partial sequencing were used to identify the causative agent of the natural disease. LD50 trials were carried out to show the virulence of this isolated strain in these species, with values of 1.7 × 104 CFU per fish in red porgy and 1.32 × 105 CFU per fish in gilthead seabream. The most prominent lesions were meningoencephalitis and multifocal infiltration of macrophage cells in the kidney and spleen.     

亲水性液相色谱串联质谱法测定红甜菜中甜菜碱含量

为了建立红甜菜中甜菜碱的定量分析方法,采用改进的QuEChERS方法结合液相色谱串联质谱技术,样品经快速溶剂萃取仪以甲醇为溶剂提取,经固相萃取柱净化,采用正向亲水性液相色谱柱(Hilic),梯度洗脱,通过质谱的多反应监测(multiple reactions monitoring,MRM)正离子模式扫描进行测定,外标法定量。结果表明：甜菜碱在本方法的线性范围为0.05~5 ug/mL,添加水平为4~16 mg/g时,回收率为87.7%~95.7%,方法RSD值为3.69%~8.4%,检出限为0.01 mg/L,定量限为0.04 mg/L,与传统的分析方法相比,具有检出限低、灵敏度高的优点,完全可以适用于甜菜中甜菜碱的分析。     

Physicochemical responses of Pythium porphyrae (Oomycota), the causative organism of red rot disease in Porphyra to acidification

Physicochemical responses to acidification in Pythium porphyrae , the causative organism of red rot disease in Porphyra , were investigated. The acid tolerance of P. porphyrae mycelia under pH 4 (acidic condition) condition increased significantly compared with that of the mycelia under pH 8 (condition equivalent to seawater) condition. Free amino acid levels in the mycelia decreased 1.3–8.8-fold under pH 4 condition. However, some free amino acids such as the d -cysteinolic acid-like component, phosphoethanolamine, glutamic acid, aminoadipic acid and methionine increased 2.6–21.7-fold under the same condition. Proton flux on the mycelia exposed to pH 8 increased significantly compared with the mycelia exposed to pH 4. The patterns of proteins present (examined by two-dimensional polyacrylamide gel electrophoresis) differed among the pH conditions. These results suggest that P. porphyrae acquires acid tolerance and is able to adapt to the changing pH conditions. This has significant implications for the use of acidic fungicide treatment for prevention of red rot disease on Porphyra farms.     

利用紫外线和氯化锂诱变筛选高产Monacolin K的红曲突变株

In the 1970's, a Japanese scientist discovered that some strains of Monascus spp. when they grew on rice might produce a certain secondary metabolite, known collectively as Monacolin K,