Effects of functional ingredients from yeast in diets for Atlantic salmon (Salmo salar), from two genetic backgrounds, on growth performance and nutrient utilization ; Effekter av funksjonelle ingredienser fra gjær i dietter for Atlanterhavslaks (Salmo salar), fra to genetiske bakgrunner, på vekst og fôrutnyttelse

The overall aim of this thesis was to determine effects of functional ingredients in diets for Atlantic salmon, extracted from non- saccharomyces yeast, on growth performance and feed utilization. A 13 week (7 weeks in freshwater and 6 weeks in seawater) long feeding trial on pre- and post-smolt from two family groups (Gain and Prime) was conducted. Triple groups of salmon (initial weight ~ 30 grams) were fed one control diet containing a commercial like basal diet, the two other diets (diet 2 and diet 3) were added 0.1 % yeast. There were found no significant (p>0.05) differences in feed intake, growth rate of feed efficiency between diets within the same family. However, final weight measurements show that fish fed diet 3 had grown, statistically significantly larger than fish from the control group, in both families. Significant differences between Gain and Prime were relatively large (p<0.001). Gain had the highest growth rates but also the highest FCR (lower feed efficiency) in FW. Indicating positive effects of selective breeding programs for selection of improved growth in Atlantic salmon. However, opportunities for directly selection for feed efficiency should be explored, and not indirectly selected for via growth. Despite large family effects on all performance indicators in FW, family effect was not significant on ADC of crude protein, phosphorus and protein retention. Digestibility or nutrient retention could consequently not explain why the fish with the highest feed intake had lower feed efficiency in FW. ; M-AA