Strong and even fillet colour

Download as PDF

Updated documentation, per March 2019

 

Better and more even pigmentation is an important goal for most farmers.  With an increasing degree of processing and product differentiation, a high, stable and predictable pigment level in the fillet becomes increasingly important for both the processing industry and consumer.  A strong red colour also means that the fillet contains a high level of astaxanthin, which is documented to have positive health related benefits for both salmon and humans.  A precise selection of brood fish using three colour-QTLs will ensure a strong and even colour in the fillet.

Figur-1-RED-2015-bilde-English

Figure 1. Average fillet colour in relation to the number of colour-QTLs, Q, in salmon from three different generations. A total of 6,000 salmon at around 3.5kgs contributed to the data. Each of the three colour-QTLs has 1 or 2 copies of the favourable gene marker, Q. In fish with QTL-innOva® RED the number of copies of Q lies between 3 and 6, but mostly 4 and 5 Q.

Salmon genes that affect pigmentation

A salmons’ ability to accumulate pigment that is supplied in feed varies between different life stages and seasons.  It has also been documented that there is a significant genetic variation and heritability of the trait.  Several independent studies have shown that between 35% and 55% of variation in fillet colour can be explained with genetics.  With modern breeding technology where selection is based to a greater degree directly on genes or genetic-marker tests, we have far better methods to achieve rapid progress on important traits.

Specially developed genotyping tool

Throughout 20 years, more than 15,000 DNA samples were taken from AquaGen fish with accurate recording of pigment levels for each fish.
This material has been stored in the Biobank that AquaGen established in association with the breeding companies Geno and Norsvin. In order to search for QTLs significantly connected with fillet colour a SNP chip (genomic search tool), containing a total of 950,000 genetic markers specially designed for the AquaGen strain was used.

Three genetic markers for fillet colour

Figur-2-RED-2015-bilde-English

Figure 2. Fillet colour groups of salmon (total 203 fish) of different size from 200g to 7 kg, compared to the number of the favourable gene marker, Q, from three colour-QTLs. QTL- innOva® RED will contain 3 to 6 Q, but mostly 4 and 5 Q.

Three significant QTLs were found, all having a moderate to strong effect on fillet colour (Figure 1). By combining the identified QTLs in the selection of brood fish, it was possible to document a substantially increased average level of astaxanthin in the fillet. At the same time variation between fish within the same group was reduced. The effect of the three colour-QTLs was also tested in fish of differing size, and results show that the beneficial effect is independent from weight. This provides flexibility in the timing for harvesting (Figure 2).

 

How do the colour-QTLs work?

Functional studies of the genes associated with the three colour-QTLs, show that they increase absorption and reduce breakdown of astaxanthin in the intestine.  Astaxanthin is a strong antioxidant that protects cells against oxidative stress and contributes to a strong immune system.  Research has shown that astaxanthin has beneficial health effects both for salmon and those that eat it.

Products with strong and even fillet colour:

  • AquaGen® Atlantic QTL-innOva® RED

(can be chosen in addition to other products)

Benefits of QTL-innOva® RED:

  • Higher average and reduced variation in fillet colour in batches
  • More effective utilisation of pigment content in feed, especially during periods with strong growth
  • Greater flexibility with timing of harvesting