Effects of alternative oil sources in feed on growth and fatty acid composition of juvenile giant river prawn (Macrobrachium rosenbergii)

To relieve the pressure on the future use of fish oil (FO), alternative oil sources need to be explored. Alternative oil sources were evaluated-Schizochytrium sp. (SZ) and soybean oil (SO)-on the growth performance and flesh quality of juvenile river prawn, Macrobrachium rosenbergii. Five experimental diets differed in the types of oil used (oil comprised 3% of dietary ingredients): 3% FO, 1% SZ + 2% SO, 1.5% SZ + 1.5% SO, 2% SZ +1% SO and 3% SZ. After 60 d of the experiment, the survival rates of prawns fed non-FO diets did not significantly (p > 0.05) differ from those fed the FO diet (77.82 ± 4.45-93.38 ± 0.00%). Moreover, prawns fed diets containing both SZ and SO had significantly (p < 0.05) better growth performance than those fed a single oil source. Prawns fed 2% SZ+1% SO showed the best final weight, percentage weight gain, absolute daily weight gain, specific growth rate and feed conversion ratio (p < 0.05) while those fed 1.5% SZ +1.5% SO or 3% SZ had the highest survival. Tissues of prawns fed the non-FO diets contained higher amounts of n−6 polyunsaturated fatty acid (PUFA) but were lower in n−3 long-chain PUFAs (eicosapentaenoic acid and docosahexaenoic acid) than those fed the FO diet. Among the non-FO groups, prawns fed 3% SZ had the most similar flesh fatty acid profile to those fed 3% FO. Substitution of FO with combinations of SZ and SO significantly improved growth performance and feed utilization. The study recommended diets containing 2% SZ + 1% SO or 1.5% SZ + 1.5% SO for M. rosenbergii juveniles.