Assessment on the effects of dietary fatty acids on growth performance, body compositions, plasma lysozyme activity and sensorial quality of juvenile marble goby, Oxyeleotris marmorata

The present study aimed to evaluate the effects of dietary fatty acids on the growth performance, body compositions, plasma lysozyme activity and sensorial quality of juvenile marble goby. Four experimental diets were formulated to contain different dietary oleic acid (OA, 18:1n-9)/ linoleic acid (LA, 18:2n-6) ratios ranged from 0.5 to 2.4 by manipulating the dietary oil sources. Fish oil was the main oil source for control diet (FO), while the other three diets, 50% of the dietary lipid was contributed by plant oil in which soybean oil, canola oil and a mixture of soybean and canola oils were added at the expense of fish oil and expressed as SO, CO and SOCO respectively. The results showed that feed conversion ratio (FCR) of fish fed CO was significantly higher (P < 0.05) than fish fed FO and SO, indicating that high dietary OA adversely affected the feed utilization of fish which then resulted in inferior weight gain. On the other hand, dietary OA/ LA ratio did not significantly (P > 0.05) affect the whole body and fillet proximate compositions, and biological indices of fish except for hepatosomatix index (HSI) that was significantly higher in fish fed LA rich diets, SO and SOCO. Hepatic lipid of fish fed SOCO was significantly higher than that of other treatment group, although the dietary LA content in SOCO was lower than that in SO diet, suggesting that feeding fish with LA rich diet increased the HSI, and the interaction between fatty acids in the mixture of soybean and canola oils promoted the lipid accumulation in liver. Besides, high dietary LA positively affected the fillet sensorial quality. On the other hand, plasma lysozyme activity of the fish was increased with the increasing ratio of dietary omega-3 polyunsaturated fatty acids/ omega-6 polyunsaturated fatty acids.