New fermentation technique to process fish waste

The traditional method of processing fish waste is costly and usually overheats the waste, making it less digestible. In the present study, a fermentation technique using Aspergillus awamori was used to dry minced sardine fish to find a new model for processing fish waste and to evaluate its digestibility. Wheat bran (700 g), minced fresh sardines (2638 g) and A. awamori spores (0.7 g) were mixed together and kept in a ventilated incubator for 5 days at 40°C. At the end of the fermentation, a sample of fishmeal was taken to measure the nutrient content, enzyme activity and digestibility of crude protein (CP) and dry matter (DM) using an in vitro method. Furthermore, the effect of enzymes produced during the fermentation of DM and CP digestibilities of corn–soybean mixture in vitro were also examined. The percentage of moisture, CP, crude fat and nitrogen‐free extract in the fermented fish waste were 11, 39, 23 and 25%, respectively. The in vitro digestibilities of DM (69%) and CP (84%) of the fishmeal were almost the same as those of the heat‐dried sardine powder. During the fermentation, glucoamylase, α‐glucosidase, α‐amylase and acidic protease were produced, which may improve the DM digestibility of the diet. In conclusion, fish waste can be dried successfully using the fermentation technique described in the present study. Furthermore, the DM digestibility of the corn–soybean meal mixture is improved by the enzymes produced during the fermentation.     

Mitochondrial diversity of native pigs in the mainland South and South-east Asian countries and its relationships between local wild boars

In this study, we analyzed DNA sequence of mitochondrial DNA (mtDNA) control regions on the 130 native domestic pigs and eight wild boars in the mainland South and South-east Asian countries including Bhutan, Cambodia, Laos, Myanmar, and Vietnam. Forty-four haplotypes were found in the 138 individuals, 41 were in the domestic and four were in wild boars. Only one haplotype was shared by domestic and wild population in Bhutan. In other cases, mtDNA of wild boars did not show close affinity to that of the domestic pigs in the same location, indicating that the native domestic pigs in these countries did not originate in the present habitat. Phylogenetic analyzes of mtDNA haplotypes recapitulated several major clusters identified in other studies, but 11 haplotypes were grouped in a new cluster we named MTSEA. In most cases, more than one lineage group were present in a sampling station, indicating that the present indigenous domestic pigs may have multiple origins. The MTSEA haplotypes were present in relatively high frequencies in domestic pigs in the mountainous area of mainland South-east Asia (Cambodia and Laos), with a few found in Myanmar and Bhutan. The distributions of MTSEA haplotypes are in great conformity with the distribution of present-day Mon-Khmer language and indicated the existence of yet another independent domestication. The D2 haplotypes that distribute high frequency (almost 100%) throughout the Chinese breeds were dominant in Bhutan, Myanmar, and Vietnam. These results suggest an existence of human-mediated dispersal of domestic pigs from north to the south during the historical expansion of Sino-Tibetan and Tai peoples. The D3 haplotypes previously reported in north India were found in sympatric domestic and wild pigs in Bhutan. The D3 haplotype is an important proof of independent domestication event and/or great gene flow between wild and domestic pigs in the foot of Himalaya.     

Distribution and migration of age-0 jack mackerel (Trachurus japonicus) in the East China and Yellow Seas, based on seasonal bottom trawl surveys

We examined the distribution and migration of age-0 jack mackerel in the East China Sea (ECS) and Yellow Sea, based on data from seasonal bottom trawl surveys. Sampling was conducted at 79–161 stations during five cruises in spring (April–June), early summer (May–July), late summer (August–October), autumn (October–December), and winter (January–February). During early summer, jack mackerel (mean 92 mm fork length), which were estimated to have hatched in the southern East China Sea (SECS) during winter, began to occur abundantly, especially along the shelf-break region of the central East China Sea (CECS). In late summer, the distribution center of young fish (mean 126 mm) shifted northward into the shelf region of northern East China Sea (NECS), corresponding with the rise of bottom water temperature and high prey abundance. In winter when the bottom water temperature declined in the shelf region, the distribution center of jack mackerel (mean 144 mm) shifted southward, with high densities occurring in the SECS and CECS. In spring, overwintering jack mackerel that had become age-1 (mean 175 mm) were distributed abundantly along the shelf-break region of the ECS. On the other hand, jack mackerel were only sporadically found, generally at low densities, in the Yellow Sea during all seasons. High densities of jack mackerel were largely restricted to areas of >15°C bottom water temperature during all seasons. Our results indicate that the seasonal shifts of the 15°C isotherm of the bottom layer and the food conditions are significant environmental factors determining the migration of jack mackerel within the ECS.     

Estimation of nodulation tendency among Rj-genotype soybeans using the bradyrhizobial community isolated from an Andosol

The nodulation tendency of indigenous soybean bradyrhizobia on Rj -genotype soybean cultivars was investigated using approximately 260 bradyrhizobia isolated from an Andosol with 13 soybean cultivars of five Rj -genotypes (non- Rj , Rj ₂ Rj ₃, Rj ₃, Rj ₄ and Rj ₂ Rj ₃ Rj ₄). A dendrogram was constructed based on restriction fragment length polymorphism analysis of the polymerase chain reaction products (PCR-RFLP) of the 16S–23S rDNA internal transcribed spacer (ITS) region. Bradyrhizobium USDA strains were used as a reference. The dendrogram indicated nine clusters based on similarities among the reference strains. The ratio of beta diversity to gamma diversity ( H' _β/ H' _γ), which represents differences in the bradyrhizobial communities by pair-wise comparison between each cultivar, was obtained from Shannon–Wiener diversity indices. The results showed that bradyrhizobial communities among the same Rj -genotype cultivars were similar to each other, whereas bradyrhizobial communities between the Rj ₂-genotype and non- Rj , Rj ₃ or Rj ₄-genotype cultivars were significantly different. These results suggest that the Rj ₂-gene might not only affect the nodulation compatibility between Rj -genotype soybeans and bradyrhizobia, but also the nodulation tendency of the bradyrhizobia.