growth indices, non-specific immune parameters, skin mucus protein profile and resistance to saprolegnia parasitica in rainbow trout fed mentha longifolia

The development and implementation of nutritionally balanced diets is regarded as essential biological factors in improving growth and maintaining the health of aquaculture species. this study evaluated the effects of mentha longifolia hydroalcoholic extract on growth performance, hemato-immunological responses and skin mucus protein in rainbow trout (oncorhynchus mykiss). a total of 360 fish (10.17 ± 0.18 g) were acclimated to the experimental environment and randomly distributed across 12 tanks (four treatment in triplicate; 30 fish per tank). experimental diets were prepared by incorporating m. longifolia hydroalcoholic extract at 0 (control), 1, 2, and 3 g/kg into a basal diet and fed to the fish for a 60 day, after which they were challenged with saprolegnia parasitica. fish fed m. longifolia diets exhibited significantly higher specific growth rate and weight gain, along with reduced feed conversion ratio compared with the control. red and white blood cells counts, serum respiratory burst activity, albumin, and total protein levels were also significantly higher in extract fed groups. following challenge with s. parasitica, survival rate was markedly higher in treated fish compared to control. overall, dietary supplementation with 1 g/kg m. longifolia hydroalcoholic extract is recommended to stimulate immune response, enhance growth performance, and improve resistance of rainbow trout to s. parasitica.