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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.

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Background The "pace-of-life" syndrome (POLS) framework can encompass multiple personality axes that drive important functional behaviors (e.g., foraging behavior) and that co-vary with multiple metabolic and/or life history traits. However, the empirical evidence for the relationships between animal personality and foraging strategies remains unclear, including their fitness consequences in the POLS framework. Therefore, the POLS hypothesis might be limited, and the environmental context could influence this linkage. In this study, the Mongolian gerbil (Meriones unguiculatus), a social rodent, was used as a model system to investigate how boldness or shyness is associated with foraging strategies in the food hoarding season and over-wintering survival or reproduction at individual and group levels. Results Our results showed that bold and shy gerbils had different foraging strategies and over-wintering adaptations. Compared with shy gerbils, bold gerbils had a lower effort foraging strategy, including higher latency, less frequency, and shorter duration when foraging during the food hoarding season, and exhibited lower over-wintering survival, but bold-shy personality differences had no effect on over-wintering reproduction. Conclusion These findings suggest that animal personality is a key factor that affects the foraging strategy during the food hoarding season in Mongolian gerbils. Personality may be related to energy states or the reaction to environmental change (e.g., predation risk, food availability) in bold or shy social animals. These results reflect animal life history trade-offs between "current versus future reproduction" and "reproduction versus self-maintenance", thereby helping Mongolian gerbils adapt to seasonal fluctuations in their living environment.

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