EVALUATION OF ORGANOSOMATIC INDICES AND HISTOPATHOLOGICAL RESPONSE OF CLARIAS GARIEPINUS JUVENILES FED DIETS CONTAINING GRADED LEVELS OF MECHANICALLY EXTRACTED SUNFLOWER ( HELIANTHUS ANNUUS ) SEED MEAL

摘要

Histopathological studies provide useful information on diet quality and metabolism as well as reflect fish nutritional and physiological status. This study assessed the effects of replacing soybean meal (SBM) with mechanically extracted sunflower seed meal (MESSM) on the organosomatic indices and histopathological alterations in the liver, kidney and intestine of Clarias gariepinus juveniles for fifteen weeks. MESSM was substituted for SBM at 0, 20, 40, 60, 80 and 100% in formulating six isonitrogenous and isocaloric diets. Diets were fed twice daily to 360 C. gariepinus juveniles inside eighteen rectangular tanks (in triplicate treatments). Finally, three fish specimens per treatment were dissected and their livers, kidneys and intestines removed and processed for histopathological examinations. Their tissues were fixed, washed and dehydrated with graded alcohol, embedded in paraffin, sectioned, stained and examined using photomicrography. Data were analysed using descriptive statistics and ANOVA at P = 0.05. The results revealed that hepatosomatic index (HSI) was insignificantly (p>0.05) superior (1.87%) in the fish fed 20% MESSM diet and lowest (1.19%) in those fed 100% inclusion. Kidney-somatic index (KSI) and intestino-somatic index (ISI) were insignificantly (p>0.05) highest (0.65% and 3.63%) in fish fed 0% MESSM inclusion and least (0.38% and 2.42%) in those fed 40% inclusion respectively. Fish fed 0% and 20% MESSM inclusions maintained structurally normal liver, kidney and intestine without visible lesions. However, fish fed above 20% MESSM inclusion exhibited extensive fatty infiltration, central portal venous congestion and several large cytoplasmic vacuolations of the hepatocytes. Kidney tubules showed moderate swelling, depletion of haemopoietic and tubular compartments, conspicuous degeneration and necrosis of tubule epithelia and epithelial cells with pyknotic nuclei. Intestinal changes included hyperplastic villi, pronounced necrosis and erosion of villi and enterocytes at villi's tips. The study showed that inclusion of mechanically extracted sunflower seed meal above 20% in C. gariepinus' diet could cause severe physiological alterations, predispose fish to disease and consequently lower aquaculture profitability.