Nutritional Impact of Incorporation Thyme (Thymus vulgaris) Meal at Different Levels on Growth Performance, Biochemical Parameters and Economical Evaluation of the Nile Tilapia (Oreochromis niloticus)

     This study evaluated thyme meal (TM) as a plant protein source in fish feed, replacing 0, 10, 20, and 30% of soybean meal, which made up 40% of the control diet. The aim was to determine TM effect on the Nile tilapia growth performance. A total of 120 mon-sex fingerlings Nile tilapia, averaging 14.3± 0.64g, were acclimated and distributed into 12 aquariums (80×40×30cm, 60 liters), with 10 fish per aquarium, totaling 30 fish per each treatment group. TM contained 20% crude protein. Diets were similar in nitrogen content but varied in energy. The results showed significant improvements in total body weight gain (TBWG), average daily gain (ADG), and specific growth rate (SGR) with higher TM levels. Moreover, survival rates were 100% in all groups. The feed conversion ratio (FCR) improved significantly (P<0.05) with higher TM inclusion. Fish body composition showed higher moisture, CP, and ash content, while dry matter (DM), organic matter (OM), EE, and gross energy decreased in TM groups. Furthermore, energy retention and protein production value (PPV) increased significantly (P<0.05). Blood protein levels rose in all TM groups, with the highest values of protein and globulin in 10% group and non-significant effects on AST and uric acid compared to control. Feed costs decreased, enhancing cost-efficiency. In conclusion, thyme meal is an effective alternative plant protein source for tilapia diets, improving growth performance, feed efficiency, and biochemical parameters.