Økt bærekraft i lakseoppdrett ved å løse flaskehalser i oppdrett av triploid laks / Solving bottlenecks in triploid salmon production - a way to strengthen the sustainability of the salmon aquaculture industry

Prosjektet ble finansiert av FHF gjennom Havbruksprogrammet i Forskningsrådet, og har bidratt med viktig kunnskap om triploid laks sammenlignet med diploid. Det er vist at genreguleringen i triploid laks er kompleks, og ulik i ulike typer vev i laksen. Både postsmolt og voksne triploider presterer bedre enn diploider ved lave temperaturer og dårligere ved høye. Lik eller bedre prestasjon av triploider ved lave temperaturer kan gjøre dem aktuelle både i områder med moderate maksimumstemperaturer, og også i lukkede gjennomstrømningsanlegg med tilstrekkelig oksygennivå hele året. For god prestasjon hos triploider er det viktig med god tilgang på histidin for å unngå katarakt. For tilfredsstillende beinbygning er det viktig at tilgjengelig fosfor i fôret er høyt nok, særlig perioden mellom 3 og 10 gram ser ut til å være kritisk.

 

Results achieved
Summary from the project’s final report
The current project aimed to study how triploid salmon are able to regulate their gene expressional out-put to a similar level as in diploids, and to elucidate the mechanisms involved in the induction of skeletal deformities and cataracts and the reduced thermal tolerance of triploid Atlantic salmon.

The project has showed that triploid Atlantic salmon shows non-additive gene expression. Further the general mechanism of non additive expression does not seem to be due to hypermethylation of the whole genome. Although some specific changes in methylation seems to occur possibly related to protein turnover heart formation, bone/cartilage formation and micro RNA regulation. The results show that the differences in gene regulation is very complex, and may differ between tissues. Further studies should focus on one tissue only.

Both postsmolt and adult triploids perform similarly or better than triploids at low temperatures and poorer at high temperatures. It is suggested that triploid Atlantic salmon post-smolts and adults have a similar energy metabolism during varying environments, but differ homeostatically in their physiological response to suboptimal conditions. Nonetheless similar or even better performance at lower water temperatures could favour the use of triploid Atlantic salmon not only in open net pen aquaculture in geographical areas with moderate maximum water temperatures, but also in closed flow-through systems with sufficient oxygen levels throughout the year.

In freshwater, a grave cataract outbreak was recorded in groups at 16°C, although with a reduced severity in both ploidies when fed a high histidine diet. At 10°C, ploidy and diet groups performed similarly to each other with respect to growth and mortality, however triploid status and low dietary histidin were associated with increased cataract score.

When fed 0.6 per cent P from 3 g, triploids had lower vertebra ash content than diploids at 10 and 30 g, but had reach the level of diploids at 75 g size. The parallel increase in vertebra Ash between diploids and triploids between 10 and 30 g, when feed 0.6 per cent P throughout, points to that the period between 3 and 10 g is most critical for triploids. There was a tendency for triploids having lower vertebra ash content than diploids at 10 g, also when fed the a 1.2 per cent P diet. This study shows that the period between 3 and 10 g seems critical for triploids With regard to dietary P and that available P in this period should be considerably above 0.6 per cent.