Effect of methionine nano-encapsulation with chitosan on the amino acid durability in diet and growth performance in rainbow trout (Onchorhynchus mykiss) larvae

The present study focused on the effect of methionine nano-encapsulation on growth performance in rainbow trout fingerlings as a commercial fish species. A total number of 3600larvae (1±0.01 g in weight) were allowed to acclimatize to experimental conations and were then fed with experimental diets. Methionine release was tested both in vitro and in vivo after the amino acid durability and chitosan nanoparticle preparation. Under in vivo conditions, the fish were divided into four groups in separate nursery ponds with each group (with 3 replicates)containing 100 fish. Fish in the first, second, third and fourth groups were fed a commercial trout diet (Rosha, S1 and S2),a diet supplemented with chitosan nanoparticles, a diet supplemented with methionine, and a diet supplemented with chitosan-encapsulated-methionine, respectively. The fish were fed 5 times a day based on 5 % of biomass for 8 weeks. At the end of the experiment, gut, stomach and blood serum samples were taken from all the treatments. The samples were then centrifuged and the resultant supernatants were subjected to amino acid analysis. The fish survival and growth performance were calculated at the end of experiment. The results revealed that the fish survival in the control and chitosan treatments were significantly lower than the other treatments (P<0.05). Dietary methionine supplementation significantly affected the fish specific growth rate (P<0.05). Methionine release rate in gut was higher than that of stomach. Methionine encapsulation with chitosan significantly increased the amino acid durability (P<0.05).