Investigation of the use of dandelion (Taraxacum officinale) plant extract in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) feed

This study was carried out in two stages (Phase-1 and Phase-2) to investigate the possibilities of using dandelion (T. officinale) plant extracts in rainbow trout (O. mykiss) feeds. Phase 1 examined how dandelion root, leaf, and flower extracts affected fish growth performance, feed efficiency, body composition, and hematological blood parameters. Phase 2 examined the effects of various doses of root extract on both Phase 1 parameters and biochemical blood parameters, intestinal histologies, and liver histologies. Fish resistance to infection with Lactococcus garvieae was also studied. 360 (20.00±1.025 g and 11.77±0.880 cm) rainbow trout fry were used in the Phase 1 study, and 540 (22.05±1.740 g and 13.03±0.470 cm) rainbow trout fry were used in the Phase 2 study. Four trial groups with triplicate in Phase 1 study (Control, Root(Ex)10 ml/kg; Leaf(Ex) 10ml/kg and Flower(Ex) 10ml/kg), and six trial groups with triplicate in Phase 2 study (Control, feed with 2.5 ml/kg, 5 ml/kg, 10 ml/kg, 20 ml/kg and 40 ml/kg root extract) were formed. In both trials, 30 fish were stocked in 80L water-volume tanks, and they were fed for 90 days. The results showed significant final body weight (FBW), weight gain (WG), specific growth rate (SGR), lowest feed conversion ratio (FCR), protein evaluation rate (PER), and protein deposit rate (PDR) in the 20 ml/kg group and the Phase 1 study Root(Ex) group (P<0.05). In the phase 2 study, lipit deposit rate (LDR) was found to be lower in the extract groups compared to the control group (P<0.05). In comparison to the control group, the condition factor (CF), viscerosomatic index (VSI), and hepatosomatic index (HSI) values were shown to be significant in Phase 2 (P<0.05). In Phase 2 and Phase 1(especially in the Root(Ex) group), crude protein ratios (%HP) increased in fish muscle and liver, while crude lipit ratios (%HY) decreased compared to the control group (P<0.05). When compared to the control group, hematological blood parameters were found to be higher in Phase 1. (P<0.05). In phase 2, the differences in mean erythrocyte volume (MCV), mean erythrocyte hemoglobin (MCH), mean erythrocyte hemoglobin concentration (MCHC), and platelet (PLT) values were significant (P<0.05). In the blood serum, High-density lipoprotein (HDL), alkaline phosphatase (ALP), and total protein (TP) levels were found to be high in the extract groups compared to the control group, while levels of glucose, cholesterol, triglyceride, low-density lipoprotein (LDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and amylase were found to be lower (P<0.05). In the intestinal histology, with the addition of root extract, stratum compactum (SC), submucosa (SM), lamina propia (Lp), villi length (Vb), villi width (Vg), villi area (VA), mucosal folds, muscle thickness (TM), and goblet cell density (Gb) were positively affected by increasing extract, and 20 ml/kg group was determined as the best group. In the liver histology, regions of vacuolization, hepatocellular degeneration, apoptotic hepatocyte nuclei, and necrotic tissue were shown to be reduced in the extract groups compared to the control group. The Challenge test revealed that the addition of 2.5 ml/kg extract significantly increased the disease resistance to infection with Lactococcus garvieae. The kuadratik regression result determined that 20-25 ml/kg (24.06±0.93) extract addition was the appropriate amount that could positively affect fish growth performance, body composition, hematological and biochemical blood parameters, liver and intestinal histological structures, and it was concluded that the extract can be used as an alternative feed additive.