Effect of substitution of dietary fish meal by soybean meal on different sizes of gibel carp (Carassius auratus gibelio): digestive enzyme gene expressions and activities,and intestinal and hepatic histology

A 7‐week growth trial was conducted to evaluate the effects of dietary soybean meal (SBM) on digestive enzyme activity of intestinal mucosa, mRNA levels of digestive enzymes in hepatopancreas, and the mid‐intestinal and hepatopancreas histology of gibel carp CAS III (Carassius auratus gibelio). Four different growth phases of gibel carp (initial body weight: fry, 0.8 g; juvenile, 5.0 g; 1‐year‐old, 62.7 g; and broodstock, 135.6 g) were tested. Seven isonitrogenous and iso‐energetic diets were formulated to contain different SBM replacement levels (0%, 20%, 40%, 60%, 80% and 100% of dietary fish meal protein), and another diet (SBMAA) contained all SBM protein and supplied crystalline amino acids. The results showed that the activities of mid‐intestine trypsin, α‐amylase and gamma glutamyl transpeptidase reduced with increased dietary SBM, while the chymotrypsin activity increased first and then decreased. The ultrastructures of intestinal epithelial cells and hepatopancreas cells in fry and broodstock fish were distinctly affected by 200 g kg^‐1 dietary SBM. Supplementation of dietary amino acid to the highest replacement groups was not sufficient to improve digestive and absorptive capacities and growth performance. Gibel carp may be adapted to dietary SBM through increase in gene expression of hepatopancreas digestive enzymes and has potential to utilize proceeded SBM as feedstuffs.     

Dietary α‐linolenic acid affects lipid metabolism and tissue fatty acid profile and induces apoptosis in intraperitoneal adipose tissue of juvenile grass carp (Ctenopharyngodon idella)

A 56‐day feeding trial was conducted to elucidate the effects and mechanism action of dietary α‐linolenic acid (ALA, 18:3n‐3) on lipid accumulation and fatty acid profile of muscle, hepatopancreas and intraperitoneal fat (IPF) in juvenile grass carp using three isonitrogenous and isoenergetic semi‐purified diets containing 0.0% (control group), 1.0% and 2.0% ALA, respectively. The lowest intraperitoneal fat (IPF) ratio was found in 2.0% group. In the muscle, hepatopancreas and IPF, docosahexaenoic acid (DHA, 22:6n‐3) and eicosapentaenoic acid (EPA, 20:5n‐3) contents increased with the increase in dietary ALA. In the IPF, caspase 3, caspase 8 and caspase 9 showed the highest activities in 2.0% group, while the value of Bcl‐2/Bax (B‐cell leukaemia 2/Bcl‐2‐associated X protein) reached the lowest. Meanwhile, swelling of the IPF mitochondria was observed in 2.0% group. The gene expressions of fatty acid desaturase (FAD) and fatty acid elongase (ELO) in the hepatopancreas and muscle showed significantly higher levels in the treatment groups, whereas an opposite trend was existed in the IPF. Fatty acid synthase (FAS), sterol regulatory element binding protein‐1c (SREBP‐1c) in the IPF and hepatopancreas reached the lowest in 2.0% group. Overall, dietary ALA could promote n‐3 highly unsaturated fatty acids (HUFAs) synthesis and suppress the accumulation of lipid by decreasing the expression of related genes and promoting the apoptosis in IPF.     

Natural bixin as a potential carotenoid for enhancing pigmentation and colour in goldfish (Carassius auratus)

Discovering natural carotenoids for colour enhancement and health benefits of fish is important to develop new feed formulations. We have purified natural bixin from achiote seeds and evaluated the effect of colour enhancing and pigmentation in goldfish. Varying levels of bixin‐based diets were prepared with 420 g kg^?1 of crude protein and 120 g kg^?1 of lipid content. Our results clearly showed that bixin (0.05, 0.10, 0.20 and 0.60 g kg^?1) based diets significantly (P < 0.05) enhanced the skin and fin colour at 30 and 60 days compared to diet without bixin. Interestingly, diet which contains 0.20 g kg^?1 bixin and commercial feed (with astaxanthin) had similar effect on carotenoid deposition in skin. Moreover, total carotenoid deposition in fin was higher than in skin of all bixin‐containing diets. However, 0.60 g kg^?1 bixin‐containing diet had lower specific growth rate (1.01 ± 0.01) and higher feed conversion ratio (2.05 ± 0.19) compared to the control group. The present results demonstrate that achiote bixin can be successfully used as an alternative natural carotenoid source against synthetic astaxanthin in fish feed. Our data indicate that 0.20 g kg^?1 is a suitable dietary level of bixin to ensure strong pigmentation, acceptable growth and feed utilization in goldfish.     

Effects of the dietary protein to energy ratio on growth,feed utilization and body composition in Macrobrachium nipponense

Oriental river prawn (Macrobrachium nipponense) has been widely cultured in Asian countries. However, its nutritional studies are very limited. In the present 8‐week study, we investigated the effects of dietary protein to energy ratio (P/E ratio) on the growth, feed utilization and body composition in juvenile M. nipponense (initial weight 0.302 ±0.03 g). Two‐factor experiment was designed and nine semi‐purified diets were formulated to contain three lipid levels (20, 80 and 140 g kg^?1) and three protein levels (330, 380 and 430 g kg^?1), producing P/E ratios from 16.5 to 23.4 mg KJ^?1 protein. The results indicated that the growth, survival rate and protein efficiency were dose dependently improved by the increased dietary lipid, but not dietary protein content. Increased dietary lipid content and/or protein content increased lipid accumulation in whole body, hepatopancreas and muscle, but did not change the feed intake and hepatopancreas weight. In conclusion, our present study indicated that M. nipponense is a species with relatively high‐energy requirement. It could utilize dietary lipid content up to 140 g kg^?1, while the dietary protein with more than 330 g kg^?1 would not promote growth and protein efficiency. Taken together, 330 g kg^?1 dietary protein and 140 g kg^?1 dietary lipid level with P/E ratio 16.49 could be optimum for M. nipponense.     

Large-scale deployment of a rice 6 K SNP array for genetics and breeding applications

Background

Fixed arrays of single nucleotide polymorphism (SNP) markers have advantages over reduced representation sequencing in their ease of data analysis, consistently higher call rates, and rapid turnaround times. A 6 K SNP array represents a cost-benefit “sweet spot” for routine genetics and breeding applications in rice. Selection of informative SNPs across species and subpopulations during chip design is essential to obtain useful polymorphism rates for target germplasm groups. This paper summarizes results from large-scale deployment of an Illumina 6 K SNP array for rice.

Results

Design of the Illumina Infinium 6 K SNP chip for rice, referred to as the Cornell_6K_Array_Infinium_Rice (C6AIR), includes 4429 SNPs from re-sequencing data and 1571 SNP markers from previous BeadXpress 384-SNP sets, selected based on polymorphism rate and allele frequency within and between target germplasm groups. Of the 6000 attempted bead types, 5274 passed Illumina’s production quality control. The C6AIR was widely deployed at the International Rice Research Institute (IRRI) for genetic diversity analysis, QTL mapping, and tracking introgressions and was intensively used at Cornell University for QTL analysis and developing libraries of interspecific chromosome segment substitution lines (CSSLs) between O. sativa and diverse accessions of O. rufipogon or O. meridionalis. Collectively, the array was used to genotype over 40,000 rice samples. A set of 4606 SNP markers was used to provide high quality data for O. sativa germplasm, while a slightly expanded set of 4940 SNPs was used for O. sativa X O. rufipogon populations. Biparental polymorphism rates were generally between 1900 and 2500 well-distributed SNP markers for indica x japonica or interspecific populations and between 1300 and 1500 markers for crosses within indica, while polymorphism rates were lower for pairwise crosses within U.S. tropical japonica germplasm. Recently, a second-generation array containing ~7000 SNP markers, referred to as the C7AIR, was designed by removing poor-performing SNPs from the C6AIR and adding markers selected to increase the utility of the array for elite tropical japonica material.

Conclusions

The C6AIR has been successfully used to generate rapid and high-quality genotype data for diverse genetics and breeding applications in rice, and provides the basis for an optimized design in the C7AIR.

     

High fluid shear strain causes injury in silver shark: Preliminary implications for Mekong hydropower turbine design

The Lower Mekong Basin is facing unprecedented threats to fish diversity from hydropower development. There is increasing pressure on developers and construction authorities to design solutions to improve fish survival through turbines, thus protecting the resources in regions being developed for hydropower. A hydraulic characteristic of hydropower turbines with known fisheries impacts is fluid shear stress. Elevated shear stress occurs where rapidly flowing water passes near spillways, screens and within turbine draft tubes. Shear stress can have adverse impacts on fish, but no work has assessed whether this holds true for Mekong River species. A flume was used to determine critical tolerances of silver shark, Balantiocheilos melanopterus (Bleeker), to shear stress rates at a high‐velocity jet which simulated a hydropower turbine. Fish were assessed for injury or mortality following exposure. Results were compared against a no‐shear control. Injury and mortality were greater at higher shear stress exposures. Injuries occurred at all shear exposure levels with mortality at shear levels higher than 600/s. This approach should help design future hydropower turbines if data on other species demonstrate similar results. If the likelihood of adverse impact is high, then shear stress will need to be considered in the design of future hydropower facilities.     

Geosmin depuration from European eel (Anguilla anguilla) is not affected by the water renewal rate of depuration tanks

This study established that geosmin depuration from European eel is not affected by the water renewal rate of depuration tanks. A general fish bioaccumulation model extended with terms that account for effects of tank water renewal rate and system losses of chemicals, predicted strong effects of the water renewal rate of depuration tanks on geosmin depuration from European eel. Model predictions were validated in a depuration experiment with geosmin‐loaded European eel (n = 95) with a mean (SD) individual weight of 134.4 (5.0) g and a mean (SD) lipid content of 33.7 (2.8) % (w/w). Fish were depurated for 24, 48 or 72 h at three different tank water renewal rates (0.3, 3.3 and 33 day^?1). Treatments were installed by three different mean (SD) water flow rates (13.8 (1.3), 143.5 (9.2) and 1511 (80) L kg fish^?1 day^?1) over 30‐L tanks. Eels eliminated geosmin from their bodies, but unlike the model predicted, this was independent of the water renewal rate of the depuration tanks. Although being eliminated from the fish, geosmin hardly appeared and certainly did not accumulate in the water of the depuration tanks as the model predicted. This observation may be explained by geosmin being eliminated from eel as metabolite rather than the parent compound. Geosmin elimination from eel seems not to occur according to the generally accepted passive diffusion mechanism for excretion of lipophilic chemicals, and geosmin biotransformation by the eel seems indicated. Clearly geosmin depuration from European eel cannot be enhanced by increasing water renewal rates of depuration tanks.     

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.