The effect of Thymbra spicata hydroalcoholic extract loaded on chitosan polymeric nanoparticles on some growth performances, hematology, immunity, and response to acute stress in rainbow trout (Oncorhynchus mykiss)

Abstract

This study aimed to optimize the performance of Thymbra spicata (TS) plant extract using chitosan polymeric nanoparticles (CNPs) on growth parameters, blood, immunity, and response to acute stress in rainbow trout (Oncorhynchus mykiss). TS extract-containing nanoparticles (TSCNPs) were prepared by the ion gelation method. Juvenile rainbow trout (n = 750; 30.21 ± 3.04 g) were randomly divided into 10 treatments, including an extract- nanoparticle-free control and treatments with 100, 200, 400, and 800 mg/kg diet of TS extract with and without CNPs, and one treatment with 2.5 g/kg diet of CNPs, each with three replications. After 8 weeks of experimental feeding, final weight, weight gain, feed efficiency, protein efficiency ratio, and feed conversion ratio were significantly improved in the groups fed with 200 and 400 mg/kg diet of TSCNPs compared to the other groups (P < 0.05). Carcass composition contained significantly more protein and less fat in treatments fed with TSCNPs than the other treatments (P < 0.05). Red blood cells, hemoglobin, hematocrit, white blood cells, lysozyme, ACH50, immunoglobulin, total protein, albumin, and globulin were higher in the treatment fed with 400 mg/kg diet of TSCNPs than the other groups (P < 0.05). Post-stress levels of cortisol, glucose, and lactate increased in all treatments, but the lowest levels of these parameters after 480 min of stress were observed in the treatment with 400 mg/kg diet of TSCNPs. The findings show that the use of CNPs as carriers of TS improves the performance of the plant extract in growth, blood parameters, immunity, and stress response of rainbow trout.