Effects of natural feeding stimulants and glutamic acid supplementation on the feed intake,growth performance and digestive enzyme activities of red sea bream (Pagrus major) fed fish meal‐free soy protein concentrate (SPC)‐based diet

Two experiments were conducted for red sea bream (Pagrus major). In experiment 1, the optimum level of glutamic acid and natural feeding stimulants to enhance feed intake were determined and found that glutamic acid level of 0.5% and fish meat hydrolysate (FMH) were effective. In experiment 2, fish were fed with soy protein concentrate (SPC)‐based diet with synthetic feeding stimulants (Basal diet), the Basal diet with FMH (FMH diet), the FMH diet with glutamic acid (FMHG diet) and with fish meal diet (FM diet) as a control until satiation for 8 weeks. Feed intake of FMHG‐fed fish was significantly higher than others (p < 0.05). Specific growth rate and the feed conversion ratio of FMHG were comparable to those of FM‐fed fish (p > 0.05). Relative visceral fat ratio and crude lipid content of any SPC‐based diet‐fed fish tended to be lower than those of FM diet‐fed fish. There were no significant differences in trypsin and lipase activities hepatopancreas among treatments. SPC can be utilized as a sole protein source in a diet for red sea bream. The lower growth performance in SPC‐based diet‐ fed fish was not due to poor digestive enzyme secretion but could be associated with lipid utilization disorder.     

Criterion for estimating humidity control capacity of materials in a room

As a measure of estimating humidity control capacity of materials in an airtight room under sinusoidal temperature variation, we used the Cb value, which is the ratio of the range of variation in relative humidity in a steel box lined with the material of interest to the range in an empty steel box. In order to clarify the factors that affect the Cb value, we focused on both the temperature variation rate and the area that is lined in the box. It was found that changing the rate of temperature variation over one period strongly affected the Cb value, although the amplitude of temperature variation did not. We further noticed that the difference between the time when peak temperature was reached and the time when peak absolute humidity was reached (peak time difference), was found to be useful for estimating the humidity control capacity of materials. Knowing the difference between the phase when peak temperature was reached and the phase when peak absolute humidity was reached (phase angle difference) was also useful. Because the Cb value was affected by both the variation period and the lined area in the box, we can draw a contour diagram of the period and the lined area for materials to give an overview of the humidity control capacity of a material. The materials of primary interest in this study were Japanese cedar and porous ceramics.     

The effect of ceramic coating of fire-retardant wood on combustibility and weatherability

In order to develop a fireproof wooden material, the synergic effect of fire-retardant chemicals and wood coatings was studied. The fire performance was evaluated by cone calorimeter. Impregnation of fire retardants including polyphosphatic carbamate, and ceramic coatings including alkoxy metal salt improved the fire performance of wooden materials. This treatment made it possible to meet the guidelines for fire performance of noncombustible materials in Japan. In addition to the vacuum-pressure impregnation treatment, hot-and-cold-bath impregnation treatment is an effective way to develop fire-retardant wood by impregnating fire retardant and ceramic coating. The weatherability of the developed material was also investigated. The ceramic coating was resistant to light and moisture. Part of this report was presented at 54th Annual Meeting (Sapporo, August 2004) and the 55th Annual Meeting (Kyoto, March 2005) of the Japan Wood Research Society     

Development of a docosahexaenoic acid (DHA)-rich yellowtail <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis> using tuna by-product oil

Because a diet rich in docosahexaenoic acid (DHA) is beneficial to human health, it is desirable for yellowtail Seriola quinqueradiata intended for human consumption to contain a high amount of DHA. We investigated the effects on the growth and fatty acid composition of yellowtail of replacing some of the pollack liver oil (PO) in the yellowtail diet with a DHA-rich tuna oil (TO). Experimental diets were prepared in which PO was replaced with 0, 15, 30, and 60% TO. Replacement of PO with TO did not negatively affect growth in a 16-week trial. In contrast, the feed efficiency of the group that received 60% TO was significantly higher than that of the control group after 6 weeks. The DHA level in the whole fish body increased with increasing dietary TO level. The groups that received 30 and 60% TO replacement diets showed significantly higher DHA levels than those of the control group. DHA level in the fillet was significantly higher in the group that received 60% TO than in the control group. DHA retention tended to increase with increasing TO level. These results show that utilizing TO as a fat source can increase DHA accumulation without incurring any adverse effects on the growth of yellowtail.     

Diversity of seed cesium accumulation in soybean mini-core collections

Radiocesium is an extremely harmful radionuclide because of its long half-life; it is important to reduce its transfer from contaminated soil into crops. Here we surveyed genetic variation for seed cesium (Cs) concentration in soybean mini-core collections representing large genetic diversity. The collections grown over 3 years in rotational paddy fields exhibited varying seed Cs concentrations with significant year-to-year correlations, although the phenotypic stability of Cs concentration was lower than that of the congeners potassium (K) and rubidium (Rb). Although Cs is supposedly accumulated in plants via the K transport system, there was no apparent relationship between Cs and K concentrations, whereas a clear positive correlation was observed between Cs and Rb concentrations. Cs and K concentrations in seed showed slightly positive and negative correlations, respectively, with days to flowering. We selected several high or low Cs accumulator candidates on the basis of the 3 years of seed concentration data. These two groups showed significantly different seed Cs concentrations in another field. The differences could not be explained by flowering time alone. These results suggest that genetic variation for seed Cs concentration is present in soybean germplasm and would be useful for breeding low Cs-accumulating varieties.     

Multi-locus sequence typing of Salmonella enterica subsp. enterica serovar Enteritidis strains in Japan between 1973 and 2004

Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) was responsible for a worldwide pandemic during the 1980s and 1990s; however, changes in the dominant lineage before and after this event remain unknown. This study determined S. Enteritidis lineages before and after this pandemic event in Japan using multilocus sequence typing (MLST). Thirty S. Enteritidis strains were collected in Japan between 1973 and 2004, consisting of 27 human strains from individual episodes, a bovine strain, a liquid egg strain and an eggshell strain. Strains showed nine phage types and 17 pulsed-field profiles with pulsed-field gel electrophoresis. All strains had homologous type 11 sequences without any nucleotide differences in seven housekeeping genes. These MLST results suggest that S. Enteritidis with the diversities revealed by phage typing and pulsed-field profiling has a highly clonal population. Although type 11 S. Enteritidis may exhibit both pleiotropic surface structure and pulsed-field type variation, it is likely to be a stable lineage derived from an ancestor before the 1980s and/or 1990s pandemic in Japan.     

Effects of dietary phosphorus level on non-faecal phosphorus excretion from yellowtail (Seriola quinqueradiata Temminck & Schlegel) fed purified and practical diets

Non-faecal phosphorus (P) was determined for large yellowtail to estimate a minimum available P requirement (Experiment  1) and to justify inorganic P supplementation in a fish meal-based diet (Experiment 2). In Experiment 1, purified diets with incremental P concentrations were fed to yellowtail (mean weight 917 g) at a feeding rate of 1.5% of body weight. The peaks of non-faecal P excretion appeared 5–6 h after feeding in fish fed more than 4.5 g available P kg⁻¹ dry diet. Broken-line analysis indicated that the minimum available P requirement was 4.4 g kg⁻¹ dry diet. In Experiment 2, a purified diet (PR) containing 6.5 g available P kg⁻¹ and a fish meal-based diet with (F1) and without (F0) additional phosphorus were fed to yellowtail (mean weight 1.1 kg) at 1.5% (PR) and 2% (F0 and F1) feeding rates respectively. There was no significant difference in P excretion between fish fed the F0 (5.5 g soluble P kg⁻¹ dry diet) and the PR diet. However, significantly higher (34.5%) amounts of non-faecal P excretions (7.4 g soluble P kg⁻¹ dry diet) were found in fish fed F1 compared with the F0 diet. This suggested that there was an excess of dietary P in the F1 diet and that supplementation is not needed in fish meal-based diets for large yellowtail.     

Seasonal changes in proteolytic enzymes of yellowtail Seriola quinqueradiata (Temminck & Schlegel; Carangidae) fed extruded diets containing different protein and energy levels

Seasonal variations in pepsin, trypsin and chymotrypsin activities and protein digestibility were studied in yellowtails (Seriola quinqueradiata) reared for 1 year with extruded diets containing different levels of protein. Trypsin and chymotrypsin storage levels in the digestive tissues of starved fish were affected by seasonal changes in water temperature. Actual digestion activities of trypsin and chymotrypsin were low at lower water temperatures, but pepsin activity in the stomach tissue was not affected by low temperatures. On the other hand, trypsin and chymotrypsin activities in the intestinal contents were higher during lower water temperature months, while pepsin activity in the stomach contents was low at lower water temperatures. Apparent protein digestibility (APD) did not differ among the dietary treatments in the higher water temperature months, while in colder months it was higher in fish fed diet 1 than in fish fed diets 2 and 3. The APD values reflected pepsin activity in the stomach contents in all sampling months. Therefore, lower APD in colder months seems to be attributed to lower protease activity in the gastric digesta, implying that enhanced pepsin secretion from the stomach tissue might improve protein digestibility and growth performance in yellowtails during winter.