Effect of bioreactor-grown biomass from Ganoderma lucidum mycelium on growth performance and physiological response of red hybrid tilapia (Oreochromis sp.) for sustainable aquaculture

Abstract

Mushroom mycelial biomass is an alternative to unsustainable use of cash crops as feed in aquaculture systems. Lately, fish-feed mixtures enhanced with heterotrophic 1-m2-bioreactor-grown biomass from the mycelium of Ganoderma lucidum (MGL) were fed to red hybrid tilapia Oreochromis sp. (tilapia). MGL biomass had high protein (32.2%), carbohydrate (48.4%) and fibre (13.8%) content compared with other common fish-feed sources (fishmeal, soybean meal, rice bran and corn). Four experimental diets containing 0 (control), 5, 10 and 15 g/kg of MGL biomass respectively were randomly allocated to eight, 70-L tanks at 15 fish per tank with duplicate treatments. All diets were formulated to be isoenergetic (~ 19 kJ/g), and the fish were fed twice per day at 3% of their body weight ratio during the feeding trial, which lasted for 42 days. The utilization of 15 g/kg of MGL in the feeding trial resulted in 100% survival rate (SR), longer body length (> 1.7 cm) and higher (35 g) body weight gain (BWG) among tilapia compared with control (30 g) after 6 weeks. Surprisingly, the feed conversion ratio (FCR) of tilapia fed with 15 g/kg (1.13) treatment was significantly lower compared with control (1.98), indicating better quality feed. The specific growth rate (SGR) of tilapia at 15 g/kg MGL (2.14) indicated a significantly greater growth compared with control (1.28). Internally, the condition factor (CF: 1.85), hepatosomatic index (HSI: 2.47) and visceral somatic index (VSI: 11.06) yielded the most significant organosomatic indices for treated tilapia compared with control, resulting in superior yield and fish health. Blood analysis of MGL-treated tilapia showed that haemoglobin (HGB: 6.43 g/dl), packed cell volume (PCV: 35%), red blood cells (RBC: 2.47 × 106 mm3) and white blood cells (WBC: 1.64.3 × 105 mm3) were significantly increased (P < 0.05) at 5 g/kg. These findings warranted that high MGL biomass diets could enhance tilapia survival and growth performance and thus may be used as a feed supplement.