Ameliorative effect of the dietary Egyptian leek ( Allium ampeloprasum L. var. kurrat ) on zinc toxicity of the African catfish Clarias gariepinus (Burchell, 1822)

Abstract

There is scant knowledge available concerning the protective role of the Allium ampeloprasum L. on African catfish (Clarias gariepinus) that is chronically exposed to zinc (Zn). Six fish groups were used: three were fed diets supplemented with leek extract (LEE 0%, 2% and 4%); and the three other groups received LEE and were exposed to a sublethal dose of zinc sulphate (7.8 mg L−1). After 45 days, fish exposed only to Zn exhibited the highest values of weight gain, specific growth rate, white blood cell count, alanine aminotransferase, alkaline phosphatase, proteins, albumin, globulin, glucose, creatinine and total antioxidant concentration significantly. Fish exposed to Zn-only also revealed insignificant changes in the condition coefficient, hepatosomatic index, gonadosomatic index and almost all haematological parameters. Moreover, exposure to only Zn resulted in a significant decrease in aspartate aminotransferase (AST). Feeding on LEE 2% increased growth, whereas LEE 4% had an insignificant effect on growth; both LEE doses caused insignificant changes in haematological and biochemical parameters. Feeding on LEE while being exposed to Zn showed a reduction in some elevated biochemical parameters compared with the Zn-only-exposed group, with LEE 2% displaying a greater protective role than LEE 4%. Histopathological investigations revealed many changes in the livers of fish fed with LEE, while it has more degenerative and necrotic changes with exposure to Zn. So, leek extract could be used at the lower dose for African catfish as a feed supplement to improve fish growth and alleviate the possible undesired effects of chronic exposure to Zn.