Selection for improved feed utilization in Atlantic salmon / Seleksjon for bedre fôrutnytting hos laks
This thesis, which is based on five experiments, discusses possible selection strategies for improving feed utilization in Atlantic salmon (Salmo salar).
Relative feed intake (DFI), thermal growth coefficient (TGC) and feed efficiency ratio (FER) were significantly higher in offspring from a selected line than those from a wild, unselected line (Paper I). The higher growth of the selected line was the result of both greater feed consumption and more efficient feed utilization for growth. This implies that selection for increased growth in Atlantic salmon may improve both of these traits.
Accumulation of yttrium in tissues was very low and not related to weight gain of individual Atlantic salmon fed diets containing YCl3 (Paper II). Since growth and feed intake is highly correlated, it is concluded that YCl3 is not suitable as a bio-marker for measuring feed intake. Long-term feed intake and feed utilization can now only be recorded for families of salmon reared in separate cages or tanks.
A significant family component indicates that the variation in DFI, TGC and FER in freshwater-reared Atlantic salmon has a genetic component (Paper III). The response in feed utilization declines as growth is increased. A significant family component for the deposition of energy per kg weight gain, indicates a possibility to improve feed utilization in Atlantic salmon by selection for less energy in weight gain.
A significant effect of sire for the apparent absorption coefficients (AAC) of K, Ca, Mg, Zn and Fe suggests that the variation in AAC of elements in seawater-reared Atlantic salmon is partly governed by genetic factors (Paper IV). The AACs of K, Cu, Mg and Zn were correlated to body weight and/or growth rate.
Estimated heritabilities for AAC of elements and a significant family component for AAC of amino acids, indicate that the variation in AAC of elements and amino acids in freshwater-reared Atlantic salmon has a significant additive genetic component (Paper V). This implies that these traits may be changed by the ongoing selection for increased growth in Atlantic salmon, and should be monitored and possibly used as selection criteria to prevent undesirable correlated responses.
Key words: Atlantic salmon, selective breeding, feed intake, feed utilization, energy and protein budgets, apparent digestion-absorption, minerals-elements, amino acids
