Replacement of fishmeal by yellow mealworm meal on the growth performance, feed utilisation and quality of large yellow croaker

Abstract

An 80-day feeding trial was conducted to evaluate the effects of yellow mealworm (Tenebrio molitor, TM) meal as substitute for dietary fishmeal on the growth performance, feed utilisation and flesh quality of large yellow croaker (initial body weight: 189.18±0.13 g). The control diet (TM0) was designed to contain 56% of fishmeal. Based on the TM0, graded levels of TM meal (15, 30, 45, 60, 75 and 100%, respectively) were used to replace fishmeal to formulate the other six experimental diets (TM15, TM30, TM45, TM60, TM75 and TM100), respectively. The results showed that the survival was not significantly affected by dietary TM meal levels (P>0.05). Compared with control group, the final body weight, weight gain rate and protein efficiency ratio decreased significantly when the replacement level over 30%, while feed conversion ratio increased significantly as replacement level over 45% (P<0.05). The total protein-bound amino acid content in muscle was significantly increased with the increase of dietary TM meal inclusion (P<0.05). With replacement level increasing, the percentage of eicosapentaenoic acid (EPA) and Σn-3/Σn-6 poly-unsaturated fatty acids (PUFA) in muscle significantly decreased (P<0.05). Meanwhile, the skin redness (a*) and yellowness (b*) values in the ventral and bottom of ventral regions showed a decreasing and increasing trend, respectively (P<0.05). The TM100 group showed a higher myofibre diameter and lower myofibre density compared to the control group (P<0.05). Total replacement of fishmeal with TM meal significantly down-regulated and up-regulated the expression of myf6 and mstn, respectively (P<0.05). The contents of inosine-5′-monophosphate and total free amino acids were significantly decreased with the increase of TM meal inclusion (P<0.05). In conclusion, TM meal can replace at least 30% of dietary fishmeal protein without negative effects on the growth, feed utilisation and flesh quality of large yellow croaker.