Effect of selection for muscle lipid content on fat deposition, dressing yields and body shape in rainbow trout

A two-way selection for muscle lipid content was performed on pan-size fish using a non-destructive measure of muscle lipid content in live fish (Distell Fish Fatmeter). The present study aimed at characterising direct and indirect responses after three generations of selection at the size where selection was applied as well as in larger individuals. Main results demonstrated that there was no indirect effect of selection on growth, irrespective of the age. Body shape however was modified by selection, FF fish being more rotund, and displaying a smaller relative head length. Muscle lipid content varied in a wide range according to the line, hybrids exhibiting intermediate values (LL<( FL=LF)<FF). There was no effect of triploidy on this trait. Increase in muscle lipid content was associated with an increase of subcutaneous fat deposition but a decrease in visceral fat content. Hybrids usually displayed intermediate values for the different traits. In large fish, carcass and fillet yields were better in FF fish.