Effects of dietary vegetable and marine lipid on growth, muscle fatty acid composition and organoleptic quality of flesh of brook charr ( Salvelinus fontinalis)

Abstract

Juvenile brook charr of 1 + year old (41.5 ± 5.5 g) were fed three experimental diets in which the principal source of lipid was qualitatively altered in duplicate experiments during a period of 9 weeks. Vegetable oils (11%) were added to two diets (SO, soya oil; CO, canola oil) while the third diet contained the same proportion of a commercial fish 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 (8:00, 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 conversion 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 three experimental diet sources (MO > CO > SO) resulted in significantly different n − 3 n − 6 ratios in the flesh of the three groups of brook charr. However, even though there were important differences in the proportions of saturated and polyunsaturated fatty acids in the three diets, the brook charr of the three experimental groups maintained relatively similar proportions of these fatty acid groups in the muscle. The significantly ( P < 0.01) higher concentrations of 11,14-eicosadienoic acid (20:2 n-6) found in the muscle of the charr fed diets containing SO and CO, indicates that brook charr have a capacity to elongate linoleic acid (18:2 n-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) to that of the SO group. The utilization of vegetable vs fish oils as major dietary lipid sources for salmonid fishes is also discussed.