Improved quality with restricted feeding of Atlantic salmon

Salmon farming has so far been focused against maximum growth, and little attention has been against the quality of the fish. To elucidate the effect of less frequent feeding on the growth and flesh quality, a full scale experiment has been performed, where the number of meals has been reduced. Normally Atlantic salmon will be fed to satiation once a day when the temperature in the sea is below 5°C, twice a day at temperatures between 5 and 10°C, and three times a day at temperatures above 10°C. This regime was compared to an alternative where feeding was restricted by means of reduced meal frequency: at seawater temperatures below 5°C the fish were fed to satiation once every second day, and above 5°C they were offered one daily meal. All fish were given the same feed, and samples were taken to look for differences in proximate composition and muscle cellularity. The feeding trial was carried out under commercial conditions with four replicates in each group in 15*15 m sea cages with 23.000 fish in each of the eight sea cages. The trial started December 2004 when the fish weighed 1 kg, and terminated in September 2005 when the fish had an average live weight of 4.5 kg. As expected, fish in the restricted group grew slightly slower with a reduction in harvest weight corresponding to 10 days of feeding at the current growth rate. There were no differences in proximate composition, but the muscle structure were significant different amongst the treatments. Restricted feeding resulted in higher muscle fibre number, with smaller diameter and higher fibre density. The restricted feeding also resulted in a significantly higher texture measured as shear force and more intense colour measured as a* and b* values with a Minolta chromameter. Restricted feeding not only enhanced the muscle quality it was also found to be economical profitable for a fish farmer. Less feed was used to produce the same quantity of fish. The feed:gain ratio was reduced from 1.09 to 1.07 and in a typical Norwegian fish farm this represents a reduction of 130.000 NOK in feed cost. In contrast, the cost for 10 days longer production time is estimated to 30.000 NOK, not considering the fact that the restricted feeding regime also is less labour intensive.