Interactive effects of dietary protein level and oil source on proximate composition and fatty acid composition in common carp (Cyprinus carpio L.)

Fish meal and fish oil represent main protein and lipid sources in fish feed, but there is a growing need for sustainable alternatives to these ingredients. In this study, four isolipid extruded diets for carp (Cyprinus carpio L.) were used: ROHP (rapeseed oil-high protein), FOHP (fish oil-high protein); ROLP (rapeseed oil-low protein) and FOLP (fish oil-low protein). The trial lasted 75 days. No statistically significant effect of oil source or protein level or interactions of these factors was observed in final body weight, growth parameters or in feed conversion ratio. Protein sparing effect and omega-3 sparing effect were observed in the present study. The results of this experiment showed no negative effects on growth parameters, or major detrimental effects on fatty acid composition of muscle tissue in common carp when fish fed with diets supplemented with rapeseed oil (RO). Furthermore, an enhanced protein sparing effect was observed, when fish fed with lower protein diets, but significant accumulation of crude lipid was observed as a result of lowering protein level. The results of this study showed that diets supplemented with rapeseed oil can be used successfully in common carp cage production.