Determination of grapefruit (Citrus paradisi) peel extract bio-active substances and its application in Caspian white fish (Rutilus frisii kutum) diet: Growth, haemato-biochemical parameters and intestinal morphology

In this study, total phenolic and flavonoid contents of grapefruit peel extract (GPE) were equal to 117.3 +/- 0.3 mu g of gallic acid/mg and 39.30 +/- 0.1 mu g of quercetin/mg respectively. Caspian white fish (n = 180, 4 +/- 0.9 g body weight) was fed with supplemented diets, including 0, 6.25, 12.5 and 25 mg of GPE/kg for 60 days at 25 +/- 1 degrees C. The growth performance was markedly improved in fish fed with 25 mg/kg of GPE compared to others (p 0.05). Moreover, fish fed with 25 mg/kg of GPE showed a significant increase in red blood cell (2.65 center dot 10(6) cell/mm(3)), white blood cell (17.75 center dot 10(3) cell/mm(3)), packed cell volume (48%) and haemoglobin concentrations (8.75 g/dl) compared to the control (p 0.05). However, the highest alanine aminotransferase (140 U/L), alanine transaminase (14.5 U/L), and alkaline phosphatase (18.5 U/L) were observed in control group. Morphological analysis of intestine revealed the highest amount of villus width (8.4 mu M), height (32.86 mu M) and surface area (342.7 mu M-2) in fish fed with 25 mg/kg of GPE (p 0.05). In conclusion, supplementing feed with GPE at 25 g/kg can improve growth performance and haemato-biochemical parameters of Caspian white fish fry.