Aquaculture feeds are formulated with a vast pool of ingredient to meet nutritional requirements of fish for normal physiological functions, including maintaining a highly effective natural immune system, growth, and reproduction. To ensure the dietary nutrients are ingested, digested, absorbed, and transported to the cells, an increasing diversity of non-nutritive feed additives are being used in aquatic feeds. Feed additives are supplemented in small amounts to tilapia for a specific purpose in aquaculture. Feed containing functional feed additives promote the growth and health of tilapia, improve their immune systems, and induce physiological benefits beyond traditional feeds. Probiotics, prebiotics, phytogenic substances, immune-stimulants, enzymes, hormones, mycotoxin binders, organic acids etc., are best functional feed additives to manage and regulate tilapia performance and improve aquaculture profit.

Feed management practices significantly impact the production performance of tilapia (Oreochromis species) culture economically; hence, adopting appropriate feed management strategies is vital to maximize returns. The advancement in aquaculture has also allowed an advancement in the development formulated feeds to supplement or replace natural feeds. Farmers are now able to prepare their own fish feeds from locally available ingredients. Hence, feed ingredient evaluation is crucial for better development of appropriate diets for different aquaculture species as well as nutritional research. Therefore, this review used secondary data to evaluate the different strategies employed for better utilization of nutrients in feed by providing a discussion of functional feed additives used in aquafeeds such as the addition of enzymes, pre/probiotics, feeding stimulants, and use of hormones. Supplementation of diet with xynalase and phytase enzymes ( P < 0.001 ) and probiotics ( P < 0.05 ) improved growth (g/d) and FCR when applied individually. The combination of enzymes and probiotics showed an interaction effect ( P < 0.05 ) on growth and FCR. A detailed discussion of feed ingredient processing strategies like fermentation, heat treatment, germination, and other biological methods meant to improve the nutritional quality of the feed and minimize antinutritional factors is provided. Furthermore, information on how genetic selection is being used to enhance feed utilization in tilapia fish is provided. The food conversion efficiency was found to be significantly higher ( P < 0.05 ) in transgenic tilapia compared to the nontransgenic red tilapia fish with average   weight ± SD of 384 ± 158   g and 314 ± 101 for transgenic fish and red tilapia, respectively, after 275 days of culture. The review further outlines the feed formulation challenges, and research gaps in tilapia nutrition. It was noted that proper feeding management strategies are very critical for the sustainability of tilapia aquaculture. In conclusion, dietary sources for tilapia are slowly shifting to plant-based products. However, these come with a lot of antinutritional factors and digestibility problems; hence, the right feeding strategies have to be employed to enable efficient nutrient utilization. The review discovered that there are a lot of strategies which employed research gaps in tilapia nutrition, especially on nutrient utilization of feed and feed formulation.

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The apparent digestibility coefficients (ADCs) of dry matter, protein, lipid and energy for soybean cake (SBC), Niger seed cake (NSC) and linseed cake (LSC) were determined in juvenile Nile tilapia. The ADCs were determined using faeces collected with a settling chamber attached to the fish rearing tank. Test diets contained 70% reference diet and 30% test ingredients, with Cr 2 O 3 as an inert marker. All treatments were triplicated. There was significant difference in Apparent Dry Matter Digestibility (ADMD), Apparent Protein Digestibility (APD) and Apparent Energy Digestibility (AED) between the test ingredients. However, there was no significant difference (P>0.05) in Apparent Lipid Digestibility (ALD) between the test ingredients. Of the three ingredients tested, SBC produced the highest nutrient digestibility coefficients (P<0.05) while LSC showed the lowest nutrient digestibilities (P<0.05). The NSC, which was the cheapest plant protein source, was a good feed ingredient for Nile tilapia diets in terms of overall nutrient composition and acceptable digestibility coefficients enabling more accurate and economical feed formulation.

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This study was conducted to evaluate the effects of different inclusion levels of water hyacinth leaf meal fermented with Aspergillus niger on feed utilization efficiency and growth performance of Nile tilapia (Oreochromis Niloticus L.). Fermented water hyacinth leaf (FWHL) at 0, 10, 20 and 30% inclusion levels were incorporated into four isonitrogenous (35% CP), and isoenergetic (18 KJ g-1 g) test diets. The fishes were stocked in 80 liters aquarium units, in a closed, recirculating indoor system. The diets were fed to triplicate groups of fish fingerlings (1.6 g average body weight) twice a day, at 6% of body weight/day, for three months. The study demonstrated that Nile tilapia fed FWHL at levels 30% had a significant negative impact (P<0.05) on weight gain, specific growth rate, feed utilization efficiency, and whole body composition. But, there were no significant changes between diets supplemented with 10% and 20% FWHL when compared with the control group. Therefore, supplementation of fermented water hyacinth leaf meal to diets of Nile tilapia is recommended up to 20% because it is cheaper than fish meal and corn.

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