Background The study was to examine the effects of Mesosphaerum suaveolens (MS) leaf extract on growth performance, whole body composition, immunological responses, hematological parameters, digestive enzymes, and antioxidant status in grass carp (Ctenopharyngodon idellus).
Methods A total of 525 grass carp, with an average body weight of 110.0 ± 1.0 g, were utilized in a 70-day feeding experiment. Fish were randomly allocated to one of five groups. Each group had a triplicate tank with 35 fish per tank. Dietary treatment composed of a basal diet was given to the control group (MS0); MS1, MS2, MS3, and MS4 were substituted with 0, 1, 2, 3, and 4 g/kg of the basal diet, respectively. Fish, relative percent survival (RPS) was measured 14 days after Aeromonas hydrophila (1x107 cells/mL) was given to the fish at the end of the feeding trial.
Results Significant enhancements were shown in growth performance indicators and the body's crude lipid and moisture of the grass carp fed increasing levels of MS compared with the control. Serum levels of total triglycerides, total cholesterol, total protein, glucose, globulin, albumin, oxalate transaminase, glutamic pyruvate transaminase, and serum content of red blood cells, hemoglobin, hemocrit, and white blood cells significantly increased, and mean cell hemoglobin and mean cell hemoglobin concentrations significantly decreased in the grass carp fed the MS-supplemented diets. The liver catalase enzyme, total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activities were increased, and liver malondialdehyde was lower in the in the MS groups compared to the control. Dietary MS supplementation improved the respiratory burst, myeloperoxidase, lysozyme, alternative complement, ceruloplasmin, antiprotease, haemagglutination, bacterial agglutination, and total immunoglobulin levels compared with the control. After being exposed to A. hydrophila for seventy days, the grass carp that was given MS extracts showed a better rate of survival than the control group at the end of the experiment; the highest survival rates were seen in the MS3 and MS4. The transcriptional examination of these gene expressions showed that the spleen and head kidney of grass carp 14-day infection had significantly elevated expression levels of major beta 2 microglobulin (β2M), Toll-like receptor 22 (TLR 22), tumor necrosis factor-alpha (TNFα), Lysozyme-C, and Lysozyme-G.
Conclusions Overall, the present research's results suggest that MS extract's growth promotion, immunological responses, hematological parameters, digestive enzymes, and antioxidant status make it an acceptable option for use as a feed additive in grass carp farms.
