EFFECTS OF DIETARY VEGETABLE AND MARINE LIPID ON GROWTH, MUSCLE FATTY-ACID COMPOSITION AND ORGANOLEPTIC QUALITY OF FLESH OF BROOK CHARR (SALVELINUS-FONTINALIS)

Juvenile brook charr of 1 + year old (41.5 +/- 5.5 g) were fed three e xperimental diets in which the principal source of lipid was qualitati vely altered in duplicate experiments during a period of 9 weeks. Vege table oils (11%) were added to two diets (SO, soya oil; CO, canola oil ) while the third diet contained the same proportion of a commercial f ish oil (MO, menhaden oil). The photoperiod was controlled (18 h light /6 h dark) and the fish were fed three times a day until satiated (8:0 0, 16:00 and 22:00 h). There were no deaths during the feeding period and the fish developed normally. The growth rate and the feed conversi on coefficients (grams of feed consumed/grams weight gain) between the three fish groups showed no significant differences. Our results show that the amount of accumulation of certain fatty acids in the muscle is influenced primarily by their concentration in the feed. Thus, the significant differences (P<0.05) among the ratio of n-3/n-6 in the thr ee experimental diet sources (MO>CO>SO) resulted in significantly diff erent n-3/n-6 ratios in the flesh of the three groups of brook charr. However, even though there were important differences in the proportio ns of saturated and polyunsaturated fatty acids in the three diets, th e brook charr of the three experimental groups maintained relatively s imilar proportions of these fatty acid groups in the muscle. The signi ficantly (P<0.01) higher concentrations of 11,14-eicosadienoic acid (2 0:2n-6) found in the muscle of the charr fed diets containing SO and C O, indicates that brook charr have a capacity to elongate linoleic aci d (18:2n-6), similar to other species of salmonids. Organoleptic tests did not show any significant difference among the tastes of the flesh from the three experimental groups of charr. Nonetheless, the texture of the meat from the CO group was firmer and was preferred (P<0.05) t o that of the SO group. The utilization of vegetable vs fish oils as m ajor dietary lipid sources for salmonid fishes is also discussed.