The evaluation of asparagus (Asparagus officinalis L.) root powder as a feed supplement on enhancing growth, immunity, and alleviating acute crowding stress in rainbow trout (Oncorhynchus mykiss)

In this study, Asparagus ( Asparagus officinalis L.) root powder was evaluated as a feed supplement at levels 10 (A10), 20 (A20), 30 g/kg (A30), and control (without supplement) for rainbow trout ( Oncorhynchus mykiss ) with initial body weight (20.30 ± 0.17 g). Based on our findings, growth performance remained unchanged across all groups ( p > 0.05). Red blood cells were found significantly higher in the asparagus-fed groups compared to the control ( p < 0.05). Hematocrit and hemoglobin levels were significantly increased in the A30 and A10 groups, respectively ( p < 0.05). Serum cholesterol and triglyceride levels were significantly lower in A20 compared to the control ( p < 0.05). Lymphoid cell phagocytic activity was significantly higher in control compared to the A10 and A20. However, myeloid cell phagocytic activity in A10 and A20 was significantly higher than control ( p < 0.05). Before stress, serum cortisol levels were similar across all groups ( p > 0.05); however, the A30 group exhibited the lowest glucose levels ( p < 0.05). One hour post-stress, cortisol levels were significantly higher in A10 and A30 ( p < 0.05), while glucose levels remained unchanged ( p > 0.05). A30 showed the lowest level of cortisol at 24 h post-stress ( p < 0.05) despite no significant changes in glucose among all other groups ( p > 0.05). In conclusion, asparagus root powder at the tested levels did not improve fish growth, although the positive impacts on hematological parameters, serum biochemistry, immune responses, and post-stress cortisol regulation in rainbow trout merit further investigation. • Rainbow trout ( Oncorhynchus mykiss ) growth performance was unchanged significantly. • Hematological factors were boosted in rainbow trout by asparagus feed supplements. • Serum biochemistry improved in rainbow trout fed asparagus root powder supplement. • Asparagus root powder stimulated the immune system in rainbow trout. • Serum cortisol decreased in rainbow trout fed asparagus under handling stress.