EFFECTS OF EMODIN ON GROWTH, HAEMOTOLOGICAL PARAMETERS AND HSP70 mRNA EXPRESSION OF WUCHANG BREAM (MEGALOBRAMA AMBLYCEPHALA) AT TWO TEMPERATURES

A 2×2 factorial design was used to evaluate the effects of dietary emodin on growth, haematological parameters and heat shock protein 70 (HSP70) mRNA expression of Wuchang bream (Megalobrama amblycephala) at two temperatures. Three hundred healthy fish (average initial weight of 7.29±0.01 g) were selected and randomly divided into four groups rearing at 25℃ and 30℃. At each temperature, the fish were fed with basal diets and supplemented with 25 mg/kg emodin, respectively. Fish were held in tanks (φ820 mm×700 mm) and fed three times daily for 77 days. The results showed that, compared with those of fish reared at 25℃, the weight gain rate (WGR) and specific growth rate (SGR), hematocritg (HCT), lactate dehydrogenase (LDH) of the fish reared at 30℃ were significantly increased, but the feed conversion ratio (FCR) and viserosomatic index (VSI), aspertate aminotransferase (AST), total bile acid (TBA) were significantly reduced. Compared with the control group, the SGR and liver body ratio (HSI), HCT, LDH of the emodin group were significantly increased, but the FCR and feeding rate (FR) significantly were reduced (P0.05). For plasma urea (UREA), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TG), complement 3 (C3), complement 4 (C4) and the mRNA level of liver HSP70, there was an interaction between temperature and emodin (P0.05). The UREA, TC, TG of the fish from the control group reared at 30℃ were lower than those at 25℃. Compared with the control, the C3, C4 and the mRNA level of liver HSP70 in emodin group were significantly increased (P0.05) at 30℃, but no significant difference was found at 25℃ (P0.05). Other indices, such as condition factor (CF), serum glucose (GLU), alanine aminotransferase (ALT) activities, white blood cell (WBC), red blood cell (RBC), haemoglobin (HGB), showed no significant difference between the groups (P0.05). The results indicated that the feed with 25 mg/kg emodin can help to alleviate the Wuchang bream blood physiological effects caused by long-term high temperature, improve the level of complements and liver HSP70 mRNA, and promote the growth of fish.