Comparison of the growth performance and long-chain polyunsaturated fatty acids (LC-PUFA) biosynthetic ability of red tilapia (Oreochromis mossambicus♀ × O. niloticus♂) fed fish oil or vegetable oil diet at different salinities

Abstract

The present study aim to compare the growth and biosynthetic ability of long-chain polyunsaturated fatty acids (LC-PUFA) of red tilapia (Oreochromis mossambicus♀ × O. niloticus♂) at different salinities. An 8-week feeding trial was conducted on the juvenile red tilapia (initial weight about 10.5 g) reared at 0, 15 and 30 parts per thousand (ppt) salinity fed with two isonitrogenous (32%) and isolipidic (9%) diets. The diet with vegetable oil was named VO, specifically rapeseed oil, without LC-PUFA but rich in C18 PUFA precursors, the other diet with fish oil was named FO rich in LC-PUFA. At the end of feeding trial, irrespective of diet, fish reared at 30 ppt showed significantly higher weight gain and specific growth rate and lower feed conversion ratio than those reared at 15 ppt or 0 ppt (p < 0.05). In addition, some LC-PUFA were significantly affected by water salinity. In fish fed the VO diet, proportions of eicosapentaenoic acid (EPA; 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and total n-3 PUFA were significantly higher in liver (p < 0.05), and DHA and arachidonic acid (ARA; 20:4n-6) significantly higher in muscle of fish reared at 30 ppt and 15 ppt than those reared at 0 ppt (p < 0.05). Furthermore, liver mRNA expression levels of genes related to LC-PUFA biosynthesis including fatty acyl desaturase 2 (fads2) and elongase 5 (elovl5) were significantly higher in fish reared at 30 ppt than those reared at 0 ppt (p < 0.05). These results indicated that red tilapia has the capability to biosynthesize LC-PUFA from C18 PUFA precursors, and such ability was higher at 30 ppt salinity than in 0 ppt salinity, and this may be associated with improved growth performance.