Improving production efficiency of farmed Atlantic salmon (Salmo salar L.) by isoenergetic diets with increased dietary protein‐to‐lipid ratio

The effects of isoenergetic diets with high (HP) and low (LP) protein‐to‐lipid ratios on feeding rate (SFR), feed conversion (FCR), growth (TGC) and relative‐ and absolute nutrient retention were investigated using both whole‐body weight (BW) and carcass weight (CW) to assess the production efficiency. Three different feeding trials in seawater were conducted: two large‐scale trials with yearling smolt (S1) and under‐yearling smolt (S0) and one small‐scale with S1 smolt. The initial body weights in the trials were 105, 319 and 978 g, respectively, and the fish were fed and monitored until they reached harvest weights. In all three trials, the dietary HP group attained significantly higher (p < .05) CW at harvest based on fish with equal BW. Also, fish fed the HP diets significantly improved FCR (p < .05) when based on CW. In the small‐scale trial, fish fed HP diet, especially during late autumn and spring, significantly (p < .001) improved FCR_BW and FCR_CW. Improved FCR coincided with significantly higher (p < .05) relative energy retention in the dietary HP group. In all three trials, the HP groups had significantly higher (p < .05) TGC with regard to both BW and CW. Taken together, the present studies indicate that growth performance and feed utilization in modern salmon farming has the potential to be further improved by increasing the dietary protein‐to‐lipid ratio. In addition, dietary influence is more precisely assessed when using carcass as the weight denominator when analysing feed utilization and growth performance.     

Reduction of early sexual maturation in male S0 Atlantic salmon (Salmo salar L.) by dietary supplementation of tetradecylthioacetic acid (TTA)

Effects of dietary tetradecylthioacetic fatty acid (TTA) on muscle fat, development of gonads and early sexual maturation in S0 Atlantic salmon during the first year in sea were investigated. TTA (0.5% w/w) was added to the feeds for 8 weeks in the spring. In May, at the end of the TTA‐feeding period, the fish in the TTA group had significantly (P < 0.05) less fat (10.1%) stored in muscle compared with the control group (10.8%). In September, mean male gonadosomatic index (GSI) in maturing fish in the TTA group was found to be lower compared with the maturing fish in the control group (P = 0.05). On the basis of GSI values, male sexual maturation in September was 10.0% vs. 14.4% for the TTA and the control group respectively. Thus, relative to the control group, the incidence of male sexual maturation in the TTA group was reduced by about 1/3 (P = 0.002). Production data was not affected by dietary supplementation of TTA. This study reveals that TTA significantly reduces the incidence of male sexual maturation in S0 Atlantic salmon. A significant elimination model of TTA in fish muscle that takes into account, the growth rate of the fish was further developed in this study.     

The dynamics of social networks among female Asian elephants

Background

South America is one of the most species diverse continents in the world. Within South America diversity is not distributed evenly at both local and continental scales and this has led to the recognition of various areas with unique species assemblages. Several schemes currently exist which divide the continental-level diversity into large species assemblages referred to as biomes. Here we review five currently available biome maps for South America, including the WWF Ecoregions, the Americas basemap, the Land Cover Map of South America, Morrone's Biogeographic regions of Latin America, and the Ecological Systems Map. The comparison is performed through a case study on the Seasonally Dry Tropical Forest (SDTF) biome using herbarium data of habitat specialist species.

Results

Current biome maps of South America perform poorly in depicting SDTF distribution. The poor performance of the maps can be attributed to two main factors: (1) poor spatial resolution, and (2) poor biome delimitation. Poor spatial resolution strongly limits the use of some of the maps in GIS applications, especially for areas with heterogeneous landscape such as the Andes. Whilst the Land Cover Map did not suffer from poor spatial resolution, it showed poor delimitation of biomes. The results highlight that delimiting structurally heterogeneous vegetation is difficult based on remote sensed data alone. A new refined working map of South American SDTF biome is proposed, derived using the Biome Distribution Modelling (BDM) approach where georeferenced herbarium data is used in conjunction with bioclimatic data.

Conclusions

Georeferenced specimen data play potentially an important role in biome mapping. Our study shows that herbarium data could be used as a way of ground-truthing biome maps in silico. The results also illustrate that herbarium data can be used to model vegetation maps through predictive modelling. The BDM approach is a promising new method in biome mapping, and could be particularly useful for mapping poorly known, fragmented, or degraded vegetation. We wish to highlight that biome delimitation is not an exact science, and that transparency is needed on how biomes are used as study units in macroevolutionary and ecological research.     

Expression of messenger ribonucleic acid encoding for steroidogenic acute regulatory protein and enzymes, and luteinizing hormone receptor during the spring transitional season in equine follicles

The period of spring transition, from the anovulatory to the ovulatory season, is characterized in many mares by cyclical growth and regression of large dominant follicles. These follicles produce only low concentrations of estradiol and it is thought that acquisition of steroidogenic competence by large follicles during spring transition is prerequisite in stimulating LH prior to first ovulation. In situ hybridization was used to localize and quantify expression of factors that play a key role in follicular steroidogenesis: StAR, P450scc (CYP11A1), P450c17 (CYP17), P450arom (CYP19), and LH receptor (LHr). One ovary was obtained from mares on the day after detection of an actively growing 30 mm transitional anovulatory follicle (defined as the transitional follicle), and the remaining ovary was removed at the third estrus of the breeding season on the day after the preovulatory follicle reached 30 mm in diameter (defined as the preovulatory follicle). Messenger RNAs encoding StAR, CYP11A1, and CYP17 were detected only in theca cells and CYP19 mRNA was confined to the granulosa layer. There was significantly lower expression of mRNAs for the steroidogenic enzymes, StAR (P<0.001) and LHr (P<0.05) in transitional follicles than in preovulatory follicles. In conclusion, large equine follicles during spring transition have low levels of mRNA encoding steroidogenic enzymes, StAR and LHr which will contribute to the steroidogenic incompetence of dominant follicles during spring transition and their subsequent regression.     

Evaluating the risk of the establishment of screwworm fly in Australia

Objective To investigate probabilities of establishment of screwworm fly throughout the year, for several locations around Australias coastline.
Methods A simulation model that predicts the spread and economic impact of an established screwworm fly population was modified to include stochastic survival functions, to investigate the risks of the pest actually establishing in this country. The effects of time of year, climate, vegetation and the number of incoming flies or larvae were investigated for four locations around Australia.
Results Analysis of variance identified a dominant three-way interaction between site, time, and the number of introduced flies. These probabilities are graphed.
Discussion In southern areas, as exemplified by Fremantle, the cold winters limit survival. A high probability of establishment exists year round in tropical regions, except in areas around the Gulf of Carpentaria and in the Northern Territory where dry weather mid-year would limit survival. Despite these comparatively lower risks, there were no areas or times where reductions in quarantine efforts could be justified.     

Essential fatty acids in Atlantic salmon: time course of changes in fatty acid composition of liver, blood and carcass induced by a diet deficient in n-3 and n-6 fatty acids

Atlantic salmon fry (4 g) were fed a semi-synthetic diet devoid of n-3 and n-6 polyunsaturated fatty acids (PUFA) for 4 months. External signs of nutritional imbalance during the period were slow growth rate and increased mortality. Some symptoms of essential fatty acid deficiency appeared in the fatty acid composition of the blood and liver during the fourth month. At that time, the percentages of n-3 and n-6 PUFA of triacylglycerols (TAG) were nearly exhausted, and the percentages of 22:6 n-3 and of 20:5 n-3 in phospholipids (PL) showed a marked decrease. This decrease in the PUFA level of the PL was paralleled by the appearance of 20:3 n-9, whereas in the TAG an increase in the percentage of 18:1 n-9 was observed. After 4 months the monounsaturated fatty acid 18:1 n-9 constituted nearly 50% of the fatty acids in the TAG fraction of the liver. The time course of the changes in fatty acid composition of liver and blood lipids was quite similar, whereas the carcass lipid composition appeared to respond slowly to a diet devoid of essential fatty acids.     

Effects of temperature and dietary n-3 and n-6 fatty acids on endocytic processes in isolated rainbow trout (Oncorhynchus mykiss,Walbaum) hepatocytes

Effects of different incubation temperatures (2, 8, 14 and 20°C) and hepatocyte membrane fatty acid composition on the rate of internalization and lysosomal degradation of the ligand, mannosylated albumin, that is taken up by receptor-mediated endocytosis, were investigated in rainbow trout (Oncorhynchus mykiss, Walbaum). The fish were kept at a water temperature ranging from 9 to 14°C and fed pelleted diets coated with either capelin oil (control), EPA/DHA-concentrate (rich in n-3 polyunsaturated fatty acids) or soybean oil (rich in n-6 unsaturated fatty acids) for at least 3 months prior to sampling. The endocytic uptake mediated by the mannose receptor was very efficient at all temperatures studied. Lysosomal degradation, on the other hand, came to a halt below 8°C. The activation energies for uptake and degradation were 54.6 and 164.2 kJ/mol respectively. No negative effects of increased amounts of either n-3 or n-6 fatty acids were observed on the endocytic parameters studied. On the contrary, multivariate analysis indicated a positive relationship between high levels of n-6 fatty acids and low unsaturation index in the phosphatidylcholine (PC) fraction of the hepatocytes and the internalization rate of 2°C, meaning that the rate of receptor-mediated endocytosis may be affected by membrane fatty acid composition.     

Increased survival by feeding tetradecylthioacetic acid during a natural outbreak of heart and skeletal muscle inflammation in S0 Atlantic salmon, Salmo salar L.

We have previously documented increased survival by feeding tetradecylthioacetic acid (TTA) during a natural outbreak of infectious pancreatic necrosis in post-smolt S1 Atlantic salmon. The aim of the present study was to test the effects of dietary TTA in S0 smolt at a location where fish often experience natural outbreaks of heart and skeletal muscle inflammation (HSMI) during their first spring at sea. The experimental groups were fed a diet supplemented with 0.25% TTA for a 6-week period prior to a natural outbreak of HSMI in May 2007. Relative percent survival for the groups fed TTA was 45% compared with control diets, reducing mortality from 4.7% to 2.5%. Expression of genes related to lipid oxidation was higher in cardiac ventricles from salmon fed TTA compared with controls. In addition, salmon fed TTA had periodically reduced levels of plasma urea, and increased cardiosomatic index and growth. Reduced mortality and increased growth after administration of TTA may be related to a combination of anti-inflammatory effects, and an altered metabolic balance with better protein conservation because of increased lipid degradation.     

Magnetic Collapse in Transition Metal Oxides at High Pressure: Implications for the Earth

Magnetic collapse in transition metal ions is predicted from first-principles computations at pressures reached in the Earth's lower mantle and core. Magnetic collapse would lead to marked changes in geophysically important properties, such as elasticity and conductivity, and also to different geochemical behavior, such as element partitioning, than estimated by extrapolating low-pressure data, and thus change the understanding of Earth's structure and evolution. Magnetic collapse results from band widening rather than from changes in crystal field splitting under pressure. Seismic anomalies in the outer core and the lowermost mantle may be due to magnetic collapse of ferrous iron, dissolved in iron liquid in the outer core, and in solution in magnesiowustite in the lowermost mantle.