Necessity of dietary taurine supplementation for preventing green liver symptom and improving growth performance in yearling red sea bream Pagrus major fed nonfishmeal diets based on soy protein concentrate

The necessity of dietary taurine supplementation for preventing green liver symptom and improving growth performance of red sea bream Pagrus major fed nonfishmeal (non-FM) diets was investigated. Yearling red sea bream (initial body weight, 580 g) were fed for 36 weeks on non-FM diets based on soy protein concentrate (SPC) supplemented with taurine at levels of 0%, 0.5%, 1.0%, 1.5%, and 2.0%. Specific growth rate (SGR) and feed conversion ratio (FCR) of fish fed the taurine-unsupplemented SPC diet were markedly inferior. In these fish, incidence of green liver was markedly higher and was accompanied by a decrease of tissue taurine concentration and an increase of hepatopancreatic bile pigment content. The green liver symptom was mainly caused by an increase of hemolysis since the erythrocytes became osmotically fragile due to taurine deficiency. Physiological abnormality and growth performance (SGR and FCR) were markedly improved by taurine supplementation to the SPC diets. These results indicate that dietary taurine supplementation is necessary for yearling red sea bream fed non-FM diet based on SPC to maintain normal physiological condition and growth performance.     

Molecular diagnosis of Myxobolus spirosulcatus associated with encephalomyelitis of cultured yellowtail, Seriola quinqueradiata Temminck & Schlegel

Mass mortality of cultured yellowtail, Seriola quinqueradiata, has recently been reported from fish farms in western Japan. Previous studies revealed that diseased fish were characterized by encephalomyelitis and presporogonic stages of a myxosporean‐like parasite in the spinal cord. However, the parasite has remained unidentified because of the lack of mature stages being present. Thus, in the present study, analysis of the small subunit ribosomal DNA (18S rDNA) of the parasite as well as in situ hybridization (ISH) studies using histological sections of the infected tissue was conducted. The 18S rDNA of the myxosporean had higher sequence similarities with those of bile‐duct‐infecting myxosporeans rather than those infecting nervous tissues and was identified as Myxobolus spirosulcatus. The ISH using specific probes demonstrated that the DNA amplified was derived from the multinuclear organisms found in histological sections. A highly sensitive and specific PCR‐based assay for M. spirosulcatus was developed, which revealed a high prevalence of infection in cultured yellowtail that exhibited the clinical signs of encephalomyelitis.     

Taurine is an essential nutrient for yellowtail Seriola quinqueradiata fed non-fish meal diets based on soy protein concentrate

The requirement of dietary taurine in yellowtail fed a non-fish meal (FM) diet based on soy protein concentrate (SPC) was examined by a feeding trial. A recovery test (RCT) was also conducted to confirm the requirement of dietary taurine in yellowtail fed the SPC diet. The non-FM diet including 58% SPC as the protein source was supplemented with 0% (NTS) and 4.5% taurine (TS). A diet including 58% FM was also included as a reference. Juvenile fish (initial BW; 470 g) were fed one type of experimental diet for 39 weeks. The RCT group was fed the taurine un-supplemented SPC (NTS) diet for the first 23 weeks, and then fed the taurine supplemented SPC (TS) diet for 16 weeks. Tissue taurine concentration of the NTS group was significantly lower (P < 0.05) than that of the FM group. Specific growth rate (SGR) and feed conversion ratio (FCR) of the NTS group was significantly inferior compared to the FM group. In the NTS group, green liver syndrome was observed in all the samples. In contrast, tissue taurine concentration of the TS group increased to a similar level to that of the FM group. Compared to the NTS group, SGR and FCR of the TS group were significantly improved (P < 0.05) by taurine supplementation to the SPC diet. Moreover, yellowtail of this group could be reared for a long term without any physiological abnormalities, and their physiological condition and performance were comparable to the fish fed the FM diet. Although the physiological condition and performance of the RCT group was markedly inferior as the NTS group at the 23rd week (wk23) of the feeding trial, the physiological condition and performance of the RCT group markedly improved by the switch of the NTS diet to the TS diet at the end of feeding trial on the 39th week (wk39). These results indicate that yellowtail fed a non-FM diet based on SPC require taurine as an essential nutrient for maintaining normal physiological condition and growth performance.     

The requirement of environmental acidification for Ibaraki virus infection to host cells

The effect of environmental acidification on Ibaraki virus (IBAV) infection was tested using endosomal inhibitory chemicals and low pH treatment. Treatment of target cells with endosomal inhibitors significantly decreased the progeny virus production. IBAV outer capsid proteins, VP5 and VP2, were removed from virion when purified IBAV was exposed to low pH environment. Further experiment showed that the exposure to low pH buffer facilitated IBAV infection when the cellular endosomal pathway was impaired by bafilomycin A1. Results obtained in this study suggest that acidic environment is essential to initiate IBAV infection.     

WIPPER: an accurate and efficient field phenotyping platform for large-scale applications

More accurate, rapid, and easy phenotyping tools are required to match the recent advances in high-throughput genotyping for accelerating breeding and genetic analysis. The conventional data recording in field notebooks and then inputting data to computers for further analysis is inefficient, time-consuming, laborious, and prone to human error. Here, we report WIPPER (for Wireless Plant Phenotyper), a new phenotyping platform that combines field phenotyping and data recording with the aid of Bluetooth communication, thus saving time and labor not only for field data recoding but also for inputting data to computers. Additionally, it eliminates the risk of human error associated with phenotyping and inputting data. We applied WIPPER to 100 individuals of a rice recombinant inbred line (RIL) for measuring leaf width and relative chlorophyll content (SPAD value), and were able to record an accurate data in a significantly reduced time compared with the conventional method of data collection. We are currently using WIPPER for routine management of rice germplasm including recording and documenting information on phenotypic data, seeds, and DNA for their accelerated utilization in crop breeding.     

Evaluation of Salmonella enterica serovar Typhimurium and Choleraesuis slyA mutant strains for use in live attenuated oral vaccines

SlyA protein plays a key role in virulence in Salmonella enterica. In this study, we evaluated the ability of the slyA mutant strain of S. enterica serovar Choleraesuis (S. choleraesuis) to protect against swine salmonellosis. Using a murine model infected with S. enterica serovar Typhimurium (S. typhimurium), we showed that the Salmonella strain with a deletion of slyA could be used as a highly immunogenic, effective and safe vaccine in mice. Based on these data, a slyA mutant of S. enterica serovar Choleraesuis strain RF-1 was constructed, and the ability of this mutant to protect immunized pigs from S. choleraesuis infection was examined. As with the S. typhimurium slyA mutant, immunization of pigs with the S. choleraesuis slyA mutant strain provided significant protection against subsequent challenge by the wild-type RF-1. These results demonstrate that SlyA is a potential target in the development of a novel live attenuated vaccine against S. enterica.     

Generation of monoclonal antibodies specific for ORF68 of koi herpesvirus

Outbreaks of koi herpesvirus (KHV) infection in carp are still a serious problem worldwide. KHV is closely related to other two cyprinid herpesviruses, pox herpesvirus (CHV) and haematopoietic necrosis herpesvirus (CyHV-2) in goldfish. In this study, two major KHV antigenic proteins (ORF62 and ORF68) were identified by immunoscreening using a KHV-specific polyclonal antibody, and then monoclonal antibodies were generated for immunodiagnostic studies. After screening hybridoma cells, one mAb against ORF68 (mAb-7C6) was obtained but no mAbs against ORF62. mAb-7C6 specifically reacted with a lysate of KHV-infected koi fin cells (KF-1 cells) but not with lysates of CHV- or CyHV-2-infected KF-1 cells in an immuno-blotting analysis. Similar results were shown in the following tests: (1) a indirect fluorescent antibody test using infected KF-1 cells and (2) an immunohistochemical investigation by fast red stain (infected liver) or FITC detection (infected spleen). These results suggested that mAb-7C6 specifically reacts with KHV ORF68 protein.     

Assisted hatching of poor-quality bovine embryos increases pregnancy success rate after embryo transfer

Embryos of good, fair and poor quality were collected from superovulated cows and subjected to zona cutting (ZC) treatment using a needle under either an inverted microscope or a stereomicroscope. One (single transfer) or 2 (twin transfer) embryos with or without prior ZC treatment were transferred nonsurgically to recipients. Without the ZC treatment, lower embryonic quality resulted in lower pregnancy success rates. However, the ZC treatment increased the pregnancy success rate following transfer of poor-quality embryos, but not the pregnancy rate after transfer of good- or fair-quality embryos. No differences were observed between the pregnancy success rates after the transfer of embryos treated under the inverted microscope and those after transfer of embryos treated under the stereomicroscope, and this was the same after single and twin transfer. Moreover, ZC treatment of embryos prior to transfer did not result in an increased abortion rate, irrespective of the number of transferred embryos. In conclusion, ZC treatment improves pregnancy success rates following transfer of poor-quality embryos. Moreover, the results indicate that ZC treatment by using a stereomicroscope is practical for on-farm application.     

Effects of exposure to zearalenone on porcine oocytes and sperm during maturation and fertilization in vitro

The influence of acute exposure to zearalenone (ZEN) on porcine oocyte maturation, fertilization or sperm penetration ability during both in vitro maturation and fertilization was evaluated. First, oocytes were cultured in ZEN-containing (0-1000 μg/l) maturation medium and then fertilized. The oocytes maturing in vitro without ZEN were then fertilized in ZEN-containing fertilization medium. The maturation rates of oocytes and penetration ability of sperm decreased significantly in the presence of 1000 μg/l of ZEN. However, neither increases in the rates of degeneration and DNA fragmentation of oocytes nor reductions in normal and polyspermic fertilization were observed. ZEN did not affect the sperm penetration rates; however, 1000 μg/l ZEN had positive effects on normal and polyspermic fertilization rates. Therefore, it can be suggested that an acute exposure of porcine oocytes during maturation and of oocytes and sperm during fertilization to ZEN up to 1000 μg/l may not affect the fertility of the oocytes.