DIETARY SUPPLEMENTATION WITH DIFFERENT LEVELS OF SMALL PEPTIDES ON GROWTH, STRESS TOLERANCE, ANTIOXIDANT, AND IMMUNITY CAPACITY IN MACROBRACHIUM ROSENBERGII ZOEAE LARVAE

To determine the optimal dietary inclusion level of small peptides for Macrobrachium rosenbergii zoeae larvae, five isonitrogenous and isolipidic experimental diets were formulated by adding small peptide protein at levels of 0 (SP0), 2.5% (SP2.5), 5% (SP5), 7.5% (SP7.5), and 10% (SP10), resulting in small peptide concentrations of 0, 0.98%, 1.97%, 2.95%, and 3.94%, respectively. A total of 125000 zoeae larvae initial weight: (0.17±0.01) mg from the same batch of spawners were selected and randomly distributed into 5 treatment groups, with 5 tanks (200 L each) per group and 5000 zoeae larvae per tank. The experiment lasted for 31 days. The results showed that the survival rate and post-larval yield rate in the SP2.5 group were significantly higher than those in the SP0 group (P<0.05). Broken-line regression on the post-larval yield rate showed that the optimal dietary inclusion level of small peptides was 0.907%. Final weight, weight gain, specific growth rate, and anti-stress death rate in the SP2.5 group were significantly lower than those in the SP10 group (P<0.05). Broken-line regression based on anti-stress death rate indicated an optimal small peptides inclusion level of 1.14%. Malondialdehyde (MDA) content was the lowest in the SP2.5 group, significantly lower than that in the SP7.5 group (P<0.05). Anti-stress death rates in the SP2.5 and SP5 groups were significantly lower than that in the other groups (P<0.05). Superoxide dismutase (SOD) activity in the SP5 group was significantly higher than that in the SP0 group (P<0.05), while the metamorphosis rate in the SP5 group was significantly lower than that in the SP0 group (P<0.05). Dietary supplementation with small peptides significantly enhanced the activities of both AKP and ACP (P<0.05). In conclusion, dietary supplementation with small peptides can improve the post-larval yield rate and stress resistance of M. rosenbergii zoeae larvae. It is recommended that the dietary inclusion level of small peptides for M. rosenbergii zoeae larvae range from 0.907% to 1.14%.