EFFECT OF SOURCE AND LEVEL OF DIETARY WATER HYACINTH ON NILE TILAPIA, Oreochromis niloticus, PERFORMANCE

Abstract

A feeding laboratorial trial in glass aquaria for 12 weeks, to replace graded levels of water hyacinth (WH) meal protein from two (polluted and not polluted) water sources instead of 0, 10, 20, 30 and 40% of soybean meal protein in Nile tilapia diets. Ten experimental diets were formulated to be isocaloric and isonitrogenous (26% crude protein) and offered daily at 2 meals, 6 days a week at 3% of fish biomass daily. Results indicated that rearing water did not influence fish by the tested treatments. Most tested heavy metals had higher levels in WH and diets especially those of polluted source. Iron levels of the WH and experimental diets were > those of Mn > Zn > Cu > Pb > Cd. The highest ether extract (EE) and nitrogen free extract (NFE) and the lowest ash contents were realized in diet contained 30% replacement with WH leaves protein from non-polluted source. Growth performance parameters differed significantly as affected by WH source and level, so the final body weights (FBW) in treatments contained 10, 20 and 30% replacement with WH levels meal protein from the polluted source were significantly lower than those of WH from the non-polluted source. Also, the pollution source for WH led to significantly lower other growth performance parameters than those of the unpolluted source for WH, whether for the bodyweight gain (BWG), survival rate (SR), or specific growth rate (SGR). Increasing level of WH leaves meal protein in the experimental diets led to significantly lower FBW, BWG, SR, SGR and condition factor. The pollution source of WH led to increases in the undeniable parts from the experimental fish (tissues' indices, hepato-somatic and female and male gonado-somatic indices), also more than 30% replacement negatively affected these indices. Contaminated source of WH decreased the feed conversion ratio (FCR) for the very low feed intake as well as for the low fish growth which led to apparent improvements in FCR, protein efficiency ratio (PER) and protein productive value (PPV). Increasing the substitution levels led to increased FCR and PPV but led to lower PER. All blood hematological and biochemical parameters of the tested fish significantly and negative influenced by source and level of WH in the experimental diets, except hemoglobin and total proteins' concentrations. Increasing level of WH leaves meal protein lowered blood total proteins in the fish as a result of lower quality of protein in such diets containing WH. Source and level of WH in the experimental diets significantly affected the chemical analysis of the whole fish body including CP, EE and ash contents. The CP decreased and both of EE and ash were increased by elevating the substation level or for dietary contaminated WH increased by elevating the substation level or for dietary contaminated WH inclusion. The increase in WH level in fish diets reduced the feed intake sharply particularly from the diets contained WH from the polluted source comparing with those contained WH from its non-polluted source. Although the low price of WH – included diets, particularly by increasing dietary WH levels; yet, the return from fish weight gain decreased, especially when WH was coming from its polluted source, which starkly reduced feed intake.