Changes in the fatty acid profiles of hybrid red tilapia, Oreochromis mossambicus x O. niloticus, subjected to short-term starvation, and a comparison with changes in seawater raised fish

Abstract

Juvenile hybrid red tilapia of mean weight 52.9 ± 2.80 g were starved for 45 days, and the liver and muscle fatty acid profiles of fed and starved fish determined on Days 0, 24 and 45. A corresponding group of fish were seawater adapted and were sampled on Day 45. In fed fish the total fatty acids in the livers (expressed in μg mg-1 lipid) decreased with growth (45 days), from 816 ± 16 to 600 ± 7 and 821 ± 25 to 589 ± 23 in females and males, respectively. This decrease was significant by the 24th day. In muscle, however, the amount of fatty acids in total lipid increased with growth, in females from 365 ± 21 to 489 ± 6 and in males from 387 ± 17 to 480 ± 17 μg mg-1 lipid. Compared with fed fish, during starvation the proportion of fatty acids in total lipid increased in both types of tissues but was still lower than at the initial level significantly so in the liver. Twenty individual fatty acids were quantified as percent of total fatty acids in liver and muscle tissues of fish from different treatments during this study. In starved fish, liver monoenes decreased significantly (P < 0.05), from 33.0 to 16.3% and 35.6 to 9.5%, and the percentage of polyunsaturated fatty acids (PUFA) increased significantly from 18.3 to 39.9% and 16.9 to 46.2% in females and males, respectively. Comparable trends were also observed in muscle, but in muscle the percentage of PUFA tended to be higher than in the liver. The fatty acids that occurred in the highest proportion were oleic acid (18:1n - 9), followed by palmitic acid (16:0) and docosahexaenoic acid (DHA; 22:6n - 3), collectively accounting for more than 50% of the total. The relative amount of PUFA, in particular DHA, increased considerably and very significantly with starvation. Principal component analysis of the fatty acid data effectively summarized the major differences among the experimental treatments, which included substantial differences in the fatty acid profiles between sexes, fed and starved animals and between fish raised in fresh- and seawater.