The first report of the growth performance and environmental sustainability effects of dietary insect meal application on the Jardine River turtle (Emydura subglobosa)

This study provides empirical data on the balancing, production, and quality of freshwater turtle diets containing partially defatted black soldier fly larvae Hermetia illucens meal (BSFL) as a fish meal (FM) replacement. A 70-day experiment was performed using 27 Jardine river turtles (Emydura subglobosa) juveniles (6 months old). Three dietary treatments were applied, namely, CON with 30% fish meal and no BSFL as the control, H75 with 22.5% fish meal and 7.5% BSFL and H150 with 15% fish meal and 15% BSFL, with 3 replicates per treatment, 3 animals per replicate, and 9 specimens in total per treatment. Post-extrusion tests showed that feed technological parameters are dependent on the BSFL meal proportion in terms of the pellet length expansion rate, volume increase, and water binding capacity. The obtained experimental feeds were well accepted by the animals. During the entire experimental period, no turtle mortality, diet-related issues, or differences in shell development or growth performance were recorded among the treatments. However, the feed intake increased in comparison to CON when 7.5% BSFL meal was used (42.30 g vs. 50.40 g), and a lower feed conversion ratio was observed in the 15% BSFL treatment (1.51 vs. 1.38). For the first time, it was empirically proven that E. subglobosa can efficiently utilize BSFL meal for up to 15% of their diet. Moreover, the possibility of an increase in environmental sustainability during turtle husbandry due to a decrease in total marine resource use of 55.8% and a 57.4% decrease in the use of fish meal per kg of body weight gain were recorded.