Effect of Excess Amounts of Essential Fatty Acids on Growth of Rainbow Trout

Abstract

Effect of dietary levels of essential fatty acids (EFA) on the growth of rainbow trout wasinvestigated. The diets containing different levels of EFA, 18:3ω3 or a mixture of ω3 highlyullsaturated fatty acids (ω3 HUFA), such as 20:5ω3 and 22:6ω3 which have an EFA efficiencytwo times higher than that of 18:3ω3, were fed to rainbow trout for 10 weeks.
The addition of 18:3ω3 or ω3 HUFA to diets at a level exceeding an amount 4 timeshigher than that required by rainbow trout resulted in poor growth and low feed conversion. In the fish fed on these diets, a high moisture content reflected low contents of protein andlipid in the whole bodies, and the symptoms were similar to those observed in the fish fedwith the EFA deficient diet. Whereas, in the livers of the fish fed on the diets containingexcess amounts of the EFA, the hepatosomatic index and the lipid content were reduced onthe contrary to the EFA deficient fish. The excess addition of ω3 HUFA to the diet wasfound to exert ill effect on the fish in a half amount of 18:3ω3.