Replacement of dietary fish oil with vegetable oils improves the growth and flesh quality of large yellow croaker (Larmichthys crocea)

We investigated the effect of the replacement of dietary fish oil with vegetable oils on the growth and flesh quality of large yellow croaker (Larmichthys crocea). The basal diet (FO) was formulated to contain 66.5% fish meal and 6.4% menhaden fish oil; whereas the other 3 experimental diets were formulated by replacing the fish oil with 50% soybean oil (SO50), 100% soybean oil (SO100) and 100% palm oil (PO100), respectively. The 4 diets were randomly assigned to 4 floating sea cages (3.0 m x 3.0 m x 3.0 m), and each was stocked with 250 fish individuals with an initial average weight of 245.29 g +/- 7.45 g. The fish were fed to apparent satiation twice a day at 5:00 and 17:00, respectively, for 12 weeks. Experimental analysis showed that the specific growth rate of fish fed SO50 or PO100 were significantly higher than that of fish fed FO or SO100 (P < 0.05), and crude lipid contents of ventral muscle and viscera were significantly lower in fish fed FO than in those fed the other 3 diets (P < 0.05). No significant differences in condition factor, viscerosomatic index, hepatosomatic index, gutted yield and colorimetric values of fish among the dietary treatments were observed (P > 0.05). Compared to FO diet, SO50, SO100 and PO100 diets led to substantial decreases in the liquid loss and water loss from fresh fillets (1 d, 4A degrees C) (P < 0.05). Similarly, thiobarbituric acid reactive substance (TBARS) values of fillets under different storage conditions (1 d, 4A degrees C; 7 d, 4A degrees C; 4 weeks, -20A degrees C; 8 weeks, -20A degrees C) decreased significantly after partial or complete replacement of fish oil with vegetable oils. These findings indicated that the growth performance and selected flesh quality properties (liquid holding capacity and TBARS value) of large yellow croaker were substantially improved by replacing dietary fish oil with vegetable oils.