Effects of China rapeseed meal replaced by Indian rapeseed meal on growth performance, body composition and health status of tilapia, Oreochromis niloticus×O.aureus

Objective To evaluate the effects of China rapeseed meal replaced by Indian rapeseed meal on growth performance, immune and liver function of juvenile tilapia, O.niloticus×O.aureus.

Method A total of 120 fish with about 17.3 g an initial body mass per fish were randomly divided into four groups. A feeding trial with four practical diets at equal nitrogen and caloric basis was conducted. Group G0 was the control group (the amount of China rapeseed meal was 35%), and G50, G75 and G100 were trial groups, for which Indian rapeseed meal replaced 50%, 75% and 100% of the China rapeseed meal in G0, respectively, and 0.1% feed attractant DMPT was added. The feeding cycle was 43 d.

Result With the percentage of India rapeseed meal increasing, the final mass, mass gain rate and specific growth rate of tilapia decreased while the feed conversion ratio increased, with significant differences only detected for the G100 group (P < 0.05) compared to the G0 group. There was no significant difference (P>0.05) in body composition, serum biochemical indices, serum malondialdehyde (MDA) contents, nitric oxide (NO) contents, superoxide dismutase (SOD) activity or alkaline phosphatase (AKP) activity among different groups (P>0.05). However, the total antioxidant capacity (T-AOC) and lysozyme (LZM) contents of the G100 group were significantly higher than those of the G0 group (P < 0.05). The liver cell structure of tilapia was damaged more seriously with the percentage of Indian rapeseed meal increasing.

Conclusion The percentage of India rapeseed meal replacing China rapeseed meal should not exceed 75% for tilapia, O.niloticus×O.aureus with 17-70 g body mass.