Incorporation of ω3 fatty acids in the diets of Nile tilapia juvenile ( Oreochromis niloticus L.): effects on growth performance, fatty acid composition, and tolerance to low temperature

In order to increase the low-temperature resistance of Nile tilapia, the purpose of this study was to determine the potential effect of ω3 fatty acid incorporation in Oreochromis niloticus diet. To perform this, two experimental diets containing soybean oil (D1) and cod liver oil (D2) have been supplied to juvenile tilapia for 30 days. According to our results, similar improvements in the two diets have been recorded for growth performance of O. niloticus including the final body mass, specific growth rate, and feed conversion ratio. Our results showed that fish fed with diet D2 promoted high polyunsaturated fatty acids mainly n-3 series (PUFA (n-3)) percent, highlighting the increased levels of docosahexaenoic (DHA) and eicosapentaenoic (EPA) as well as the activation of their conversion enzyme ratios D5D and D6D desaturases. The second objective was to assess the effect of the two experimental diets on low water temperature tolerance. This was done by exposing juvenile fish at the end of the first experiment to 16, 14, 12, 10, and 8 °C for 12 h, 24 h, and 48 h. The sub-lethal LT 50 of O. niloticus fed with diet D1 was 10.6, 11.4, and 13 °C respectively, after 12 h, 24 h, and 48 h. This pattern was commonly observed for O. niloticus fed with D2, showing that the subLT 50 were 10.3, 11.1, and 12 °C during the same period. These results demonstrate that O. niloticus juveniles fed with diet D2 are more tolerant to low temperatures than those fed with diet D1.