Abstract
This study was carried out to investigate the effect of Ulva fasciata methanol extract (UFME), as a dietary supplement on growth performance and growth-related gene expression in liver, intestinal morphometry, haemato-biochemical profile, immune response and oxidative status of Nile tilapia (Oreochromis niloticus). Four triplicate groups (Control, UFME50, UFME100 and UFME150) of fish (initial weight=1.32 +/- 0.12 g, N = 180) were fed with 4 dietary inclusion levels: 0, 50, 100 and 150 mg kg(-1) UFME respectively, for 3 months. Results showed non-significant improvement in the growth performance of fish. Growth hormone gene expression was upregulated in UFME100 fish (p < 0.05). Histomorphometrical assessment of intestinal villi absorptive capacity revealed an improvement in villus length and goblet cell number in fish fed UFME specially UFME100 (p < 0.05). UFME100 showed higher haematological parameters (p < 0.05). Antioxidant enzyme activities of superoxide dismutase (p < 0.05) and catalase (p > 0.05) were induced by UFME100 diet. Diets supplemented with three levels of UFME stimulated lysozyme activity, phagocytic activity and white blood cells count of fish with the best effect in UFME100 (p < 0.05). Conclusively, dietary inclusion of 100 mg kg(-1) UFME strongly improves health status, immune responses and antioxidant activity of Nile tilapia.