Biosynthesis and storage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is under dietary and genetic control in Atlantic salmon (Salmo salar). Enhanced EPA and DHA biosynthesis and storage may improve utilization, and thus reduce marine forage fish oil use in aquafeeds. To determine phenotypic variability in EPA and DHA tissue content and growth performance, 50 families (n = 30 salmon/family, 48 g/fish initial weight) of Atlantic salmon (Saint John River strain) were reared in freshwater and fed either a fish oil (FO) control diet or FO-free diet. After 16 weeks, body size was recorded. Salmon fed the FO-free diet overall showed significantly lower growth performance compared to salmon fed the FO control diet, regardless of family. To determine the relationship between growth and FA content, the five families with the highest and the five families with the lowest weight gain were sampled for tissue and liver FA analysis. There was a significant interaction between growth and diet. The family x diet interaction was significant for final weight, final length, weight gain, growth rate and feed conversion ratio. Among the five fastest growing families, there was a significant family effect for EPA and DHA storage in the liver but not for muscle. Among the five slowest growing families, by comparison salmon had similar liver DHA and EPA content, independent of diet treatment. Family and diet were interacting factors that determine EPA and DHA storage in liver. Certain fast-growing families also had significantly higher DHA content in liver and muscle. This study demonstrates the potential for selecting families that can better utilize a diet without marine forage fish oil.
Edwardsiella piscicida is an emergent global fish pathogen with a wide host range, although host associations driving genetic diversity remain unclear. This study investigated the genetic and virulence diversity of 37 E. piscicida isolates recovered from 10 fish species in North America. Multilocus sequence analysis (MLSA) was conducted using concatenated alignments of the gyrB, pgi and phoU sequences. MLSA clustered the tested isolates into six discrete clades. In light of recent disease outbreaks in cultured salmonids, the virulence of each clade was evaluated in Chinook salmon Oncorhynchus tshawytscha fingerlings following intracoelomic challenge of ~106 CFU/fish. Challenged and control fish were monitored for 21d, and microbiological and histological examination was performed on dead and surviving fish. Peak mortality occurred 3-5 days post-challenge (dpc) regardless of isolate or genetic group. Edwardsiella piscicida was recovered from all moribund and dead animals. At 21 dpc, fish challenged with isolates from clades II, III and IV presented cumulative mortality ≥83.3%, whereas isolates from clade I, V and VI resulted in cumulative mortality ≤71.4%. This study suggests an underlying genetic basis for strain virulence and potential host associations. Further investigations using other fish models and variable challenge conditions are warranted.
Infectious salmon anaemia (ISA) is a highly virulent viral disease of Atlantic salmon that causes massive economic losses to infected aquaculture operations. Our goal was to detect and map quantitative trait loci (QTL) that confer resistance to ISA in an admixed commercial strain of Atlantic salmon that was largely founded from the Saint John River (SJR) in North America. Full-sibling families were challenged with a virulent strain of ISA virus. Mortality was tracked during two annual trials with individual fish that survived to the end of the trial being classified as ‘resistant’, and those that died were classified as ‘susceptible’. Ten families with intermediate levels of mortality and an average size of 54.2 individuals were chosen for genotyping with a 50K SNP array designed for the SJR strain. Single nucleotide polymorphisms that were segregating within families were first used to make a composite 11K female linkage map that was then used to find the positions of QTL for ISA resistance using a half-sib model. The dam-based HS model detected a total of three QTL for ISA resistance including an experiment-wide significant QTL on Ssa25 that accounted for 8.3% of the phenotypic variance and chromosome-wide significant QTL on Ssa03 and on Ssa04 that accounted for 6.0% and 6.6% respectively. We conclude that classic linkage mapping within families continues to be an important method of detecting QTL for oligogenic traits in strains founded from multiple populations. Single nucleotide polymorphisms with moderate trait effects are being used to select within families for more ISA-resistant strains of Atlantic salmon.
Artykuł stanowi próbę analizy zmian kulturowego znaczenia instytucji cyrku, która dokonywała się w trakcie długiego historycznego procesu ewolucji cywilizacyjnej, dotykającej społeczeństwa Zachodu. Kluczowe znaczenie w analizie ma kategoria sacrum, z którą związek determinował kulturowe znaczenie cyrku. Zmiana znaczenia przebiegała od pierwotnych religijnych źródeł wczesnych form igrzysk, kiedy robienie cyrku stanowiło jedną z rytualnych formuł, wykorzystywaną do celebrowania wydarzeń istotnych społecznie, przez etap sekularyzacji tej formuły w okresie dominacji chrześcijaństwa do etapu, w którym cyrk stał się świecką instytucją masowej rozrywki.
Genetic evaluations of individual fish were calculated for growth traits in North American Atlantic salmon with and without inclusion of genetic markers. The number of SNP markers was reduced to 6,000 and further to 270 in order to reduce the problem of overparameterization. SNP genotypes were predicted for all ungenotyped animals in the pedigree. Analysis of traits used a model with polygenic effects and SNP markers together. Polygenic effects refer to the additive genetic effects that remain after accounting for SNP genotypes. SNP marker genotypes were included as covariates to evaluate fish for growth traits (weight and length) in different environments (freshwater and seawater) with genders separated. Including regressions on SNP marker genotypes reduced the sum of squares of residuals by 2.7%-12.5% and increased the variability of Mendelian sampling effects (i.e., within-family variation) compared to traditional animal model evaluations. Genetic evaluations may be carried out with a few hundred markers which may be more affordable for genotyping large numbers of fish.
