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Sunndalsøra, Norway

Gjedrem T.,Nofima Marin
Reviews in Aquaculture | Year: 2010

Individual selection for growth rate has been practised for aquatic species for many years. However, the use of a small number of breeders without records of parentage frequently results in inbreeding depression. AKVAFORSK began the first ever family-based breeding program in aquaculture in 1975 for Atlantic salmon in Norway. The first steps of the program involved estimating the phenotypic and genetic parameters of economically important traits and generating a base population by crossing wild salmon strains. As information on quantitative genetics for salmon was not available, the breeding program started by selecting for body weight. As information was gathered, other traits such as age at sexual maturation, disease resistance and product quality were added to the selection index. The salmon industry was invited to participate in the breeding program, which has been managed by Aqua Gen AS since 1993. The genetic gain achieved has been estimated at approximately 14% per generation with a global benefit/cost ratio estimated at 15/1. © 2010 Blackwell Publishing Asia Pty Ltd. Source

In aquaculture breeding, resistance against infectious diseases is commonly assessed as time until death under exposure to a pathogen. For some diseases, a fraction of the individuals may appear as "cured" (non-susceptible), and the resulting survival time may thus be a result of two confounded underlying traits, i.e., endurance (individual hazard) and susceptibility (whether at risk or not), which may be accounted for by fitting a cure survival model. We applied a cure model to survival data of Pacific white shrimp (Penaeus vannamei) challenged with the Taura syndrome virus, which is one of the major pathogens of Panaeid shrimp species. In total, 15,261 individuals of 513 full-sib families from three generations were challenge-tested in 21 separate tests (tanks). All challenge-tests were run until mortality naturally ceased. Time-until-event data were analyzed with a mixed cure survival model using Gibbs sampling, treating susceptibility and endurance as separate genetic traits. Overall mortality at the end of test was 28%, while 38% of the population was considered susceptible to the disease. The estimated underlying heritability was high for susceptibility (0.41 ± 0.07), but low for endurance (0.07 ± 0.03). Furthermore, endurance and susceptibility were distinct genetic traits (rg = 0.22 ± 0.25). Estimated breeding values for endurance and susceptibility were only moderately correlated (0.50), while estimated breeding values from classical models for analysis of challenge-test survival (ignoring the cured fraction) were closely correlated with estimated breeding values for susceptibility, but less correlated with estimated breeding values for endurance. For Taura syndrome resistance, endurance and susceptibility are apparently distinct genetic traits. However, genetic evaluation of susceptibility based on the cure model showed clear associations with standard genetic evaluations that ignore the cure fraction for these data. Using the current testing design, genetic variation in observed survival time and absolute survival at the end of test were most likely dominated by genetic variation in susceptibility. If the aim is to reduce susceptibility, earlier termination of the challenge-test or back-truncation of the follow-up period should be avoided, as this may shift focus of selection towards endurance rather than susceptibility. © 2011 Ødegård et al; licensee BioMed Central Ltd. Source

Bondevik S.,Sogn og Fjordane University College | Bondevik S.,University of Tromso | Stormo S.K.,Nofima Marin | Skjerdal G.,Sogndal Upper Secondary School
Quaternary Science Reviews | Year: 2012

Chlorophyll in dead plants ordinarily decomposes completely before permanent burial through exposure to light, water and oxygen. Here we describe 8000-year-old terrestrial mosses that retain several percent of its original chlorophyll. The mosses were ripped of the land surface, carried 50-100 m off the Norwegian coast of the time, and deposited in depressions on the sea floor by the Storegga tsunami. A little of the chlorophyll survived because, within hours after entraining it, the tsunami buried the mosses in shell-rich sediments. These sediments preserved the chlorophyll by keeping out light and oxygen, and by keeping the pH above 7-three factors known to favour chlorophyll's stability. Because the green mosses were buried alive, their radiocarbon clock started ticking within hours after the Storegga Slide had set off the tsunami. Radiocarbon measurement of the mosses therefore give slide ages of uncommon geological precision, and these, together with a sequence of ages above and below the boundary, date the Storegga Slide to the chilliest decades of the 8.2 ka cold event at 8120-8175 years before AD 1950. North Atlantic coastal- and fjord- climatic records claimed to show evidence of the 8.2 cold event should be carefully examined for possible contamination and disturbance from the Storegga tsunami. © 2012 Elsevier Ltd. Source

This experiment examined and compared the effects of a highly purified immune modulating β-1,3/1,6-glucan product (BG) and of a putative receptor blocking, mannan oligosaccharide rich product (MOS) in Atlantic salmon fed extruded diets containing extracted soybean meal (SBM) or a combination of SBM and extracted sunflower meal (SFM). The BG and MOS products were derived from the cell walls of baker's yeast. A control diet was based on LT-fish meal (FM) and contained no plant protein. Two basic experimental diets were formulated with 32% SBM (FM+S) or with 14% SBM+14% SFM (FM+SS). Following extrusion, four FM+S batches were supplemented with 500 or 1000mg BG or 1000 or 2000mgMOSkg-1, while two FM+SS batches were supplemented with 1000mg BG or 2000mgMOSkg-1. Each diet was fed to three groups of 150 salmon kept in sea pens, and effects on feed intake, growth, nutrient utilisation, gut health, sea lice infestation, and overall performance of the fish were recorded over a period of 70days. The initial weight of the fish was 0.68kg, and the different feed groups grew to final weights ranging from 1.33 to 1.72kg. Compared to the control group, fish fed the diet with 32% SBM ate 18% less, grew 30% slower, had 24% poorer feed efficiency ratio (FER), and also suffered from serious SBM-induced enteritis, diarrhoea, and reduced capacity to digest lipid. Adding BG or MOS to this diet had no detectable effects. Fish fed the diet with 14% SBM+14% SFM ate as much as the control group, but still grew 5% slower, had 7% poorer FER, and suffered from a diarrhoea-like condition and moderate enteritis. Noteworthy, 27% fewer of these fish were infested with salmon lice when compared to the other groups. Adding BG to this diet further reduced the number of lice-infested fish by 28%. Adding MOS to this diet did not affect appetite or lice infestation, but resulted 10% better FER, 8% faster growth (similar to the control group), 11% higher protein retention, less diarrhoea, and most noteworthy: elimination of the SBM-induced enteritis. This clearly demonstrates that gut health is an important production parameter for Atlantic salmon. © 2010 Elsevier B.V. Source

Odegard J.,Nofima Marin
Genetics, selection, evolution : GSE | Year: 2010

BACKGROUND: In the genetic analysis of binary traits with one observation per animal, animal threshold models frequently give biased heritability estimates. In some cases, this problem can be circumvented by fitting sire- or sire-dam models. However, these models are not appropriate in cases where individual records exist on parents. Therefore, the aim of our study was to develop a new Gibbs sampling algorithm for a proper estimation of genetic (co)variance components within an animal threshold model framework. METHODS: In the proposed algorithm, individuals are classified as either "informative" or "non-informative" with respect to genetic (co)variance components. The "non-informative" individuals are characterized by their Mendelian sampling deviations (deviance from the mid-parent mean) being completely confounded with a single residual on the underlying liability scale. For threshold models, residual variance on the underlying scale is not identifiable. Hence, variance of fully confounded Mendelian sampling deviations cannot be identified either, but can be inferred from the between-family variation. In the new algorithm, breeding values are sampled as in a standard animal model using the full relationship matrix, but genetic (co)variance components are inferred from the sampled breeding values and relationships between "informative" individuals (usually parents) only. The latter is analogous to a sire-dam model (in cases with no individual records on the parents). RESULTS: When applied to simulated data sets, the standard animal threshold model failed to produce useful results since samples of genetic variance always drifted towards infinity, while the new algorithm produced proper parameter estimates essentially identical to the results from a sire-dam model (given the fact that no individual records exist for the parents). Furthermore, the new algorithm showed much faster Markov chain mixing properties for genetic parameters (similar to the sire-dam model). CONCLUSIONS: The new algorithm to estimate genetic parameters via Gibbs sampling solves the bias problems typically occurring in animal threshold model analysis of binary traits with one observation per animal. Furthermore, the method considerably speeds up mixing properties of the Gibbs sampler with respect to genetic parameters, which would be an advantage of any linear or non-linear animal model. Source

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