Evaluation of dates and date pits as dietary ingredients in tilapia ( Oreochromis aureus) diets differing in protein sources

Seven isonitrogenous (40% crude protein) and isocaloric (18.6 kJ/g gross energy) diets were formulated to investigate the utilisation of dates and date pits as carbohydrate sources for tilapia fry ( Oreochromis aureus) and to evaluate the complete substitution of fish meal by poultry byproduct and blood meals. The growth and feed utilisation efficiency of fish fed on diets in which poultry byproduct meal was the only animal protein source were higher ( P < 0.05) than with the other two protein sources. Since these results disagree with those of previous studies with other fish species, it was assumed that the low performances of fish on fish-meal and blood-meal diets were due to inadequate processing of the raw products. The inclusion of the dates and date pits did not influence the growth of the fish. A trend of increasing body-protein content and decreasing fat was observed in fish fed diets supplemented with date-pits meal. An estrogenic action of date pits was hypothesised as the direct cause of this phenomenon.