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This study aims to develop an Excel programming model to formulate feed for Nile tilapia (Oreochromis niloticus), mainly for small- and medium-sized fish feed manufacturers. The model allows users to formulate the least costly balanced diet of Nile tilapia species, giving them the ability to choose a specific ingredient in the formulation according to the realities of the local environment: space-temporary availability of ingredients, prices and nutritional quality. Computer programming of a database of 25 locally available feed components was carried out using the Excel Solver Add-in and Excel IF mathematical functions to incorporate/delete specific ingredients in real time in accordance with user objectives. The theoretical characteristics of the least-cost balanced diets performed were within the margin of the nutrients requirement of the target fish size with protein levels of 35 per cent (fry diet: $1.07/kg), 32 per cent (fingerlings diet: $0.48/kg), 29 per cent (growth diet: $0.43/kg) and 27.12 per cent (final diet: $0.39/kg). The digestible energy of these diets was between 3016.5 ± 93.8 kcal. In addition, the model shows that an increase in soya meal prices by 75 per cent led the local feed industry to rely on imported fish meals, as the number included reached 52.28 per cent. However, the cost of the diet margin did not vary significantly. Nevertheless, it would be important to test the balanced diet developed with the model before production and scaling. [ABSTRACT FROM AUTHOR]

This study used the levels of pollutants and the histopathological analysis of the gonads and liver of Sarotherodon melanotheron sampled in Lake Nokoué and Lake Toho, both in Benin (West Africa) to assess the health status of the ecosystems. Sixty adults (30 males and 30 females) of this species were caught during the flooding seasons from both Lake Nokoué, and Lake Toho (as a reference). The physicochemical parameters of the water and the heavy metal contents (Pb, Cd, Hg) in water/sediment/fish of three sites (S1, S2, S3) in Lake Nokoué and two sites (S4, S5) in Lake Toho were analysed. Results confirm very strong organic status with organic pollution index ranging from 1.25 to 1.5. Pb, Cd, and Hg levels in the water/sediment/fish muscle tissue of Lake Nokoué were far exceeding international standards. The histopathology of gonads revealed testis-ova up to 40% in males and follicular atretic oocytes up to 33.33% in females, indicated oestrogenic effects from the pollutants with a delay of spermatogenesis and stimulation of oogenesis. The histopathology of the liver revealed the presence of regressive changes. The findings call for actions to protect the ecosystem from pollution and attention in terms of health of humans consuming fish products from Lake Nokoué. [ABSTRACT FROM AUTHOR]