The effect of dietary Tenebrio molitor meal inclusion on growth performance and liver health of largemouth bass (Micropterus salmoides)

This study investigated the effect of dietary mealworm meal on growth performance, body composition, and liver health of largemouth bass. During the feeding trial, all fish were feed to apparent satiation twice one day for 42 days with 4 experimental diets included 0, 10.35, 20.70, 31.50% mealworm meal (MWM) replacing graded levels of fishmeal (FM) (0%, MWM0; 25%, MWM25; 50%, MWM50; 75%, MWM75), respectively. The growth performance (weight gain rate, specific growth rate and feed efficiency) of largemouth bass were significantly decreased in the MWM50, and MWM75 groups. Liver lipogenesis and lipid contents were significantly higher in MWM75 group than in the MWM0 group. In MWM50 and MWM75, the structure of liver tissue was abnormal, and a large number of inflammatory cells infiltrated into the tissue. The transcriptional levels of tumour necrosis factor-alpha, interleukin-1 beta, and interleukin-15 were significantly upregulated in MWM75 compared to MWM0. The activity of caspase 3 (casp3) and apoptosis was significantly higher in the MWM75 group than in the MWM0 group. The relative mRNA levels of casp3, casp9, casp8 and casp10 were upregulated in MWM50 and MWM75. It is concluded that MWM can replace 25% of FM in the diet of largemouth bass without negative effects on growth performance. However, high inclusions of MWM replacing more than 50% of dietary FM would lead to negative influences on growth and liver health of largemouth bass, partly through enhanced inflammation and apoptosis.