South Korea: Inclusion of mealworm meal in diets of rainbow trout fry increases fish growth, protein efficiency, and immunity.
Published in Fisheries and Aquatic Sciences, Jeong et al found in an 8-week trial that incusion of mealworm meal significantly increased fish growth, protein efficiency ratio in rainbow trout fry.
From Jeong et. al 2020:
Rainbow trout (Oncorhynchus mykiss) is a commonly raised fish species in aquaculture. In addition to the fish raised for consumption, millions of rainbow trout are raised for stocking into ponds, lakes, streams, and rivers to provide additional sport fishing opportunities where few may otherwise exist. Together, rainbow trout cultured directly for human consumption, and those cultured to enhance or provide sport fishing opportunities, account for a measurable proportion of global aquaculture production, with a total production exceeding 800,000 tons in 2016 (FAO FishStatJ 2018). To date, many studies have focused on evaluating a variety of different plant and animal protein ingredients to meet the rainbow trout’s nutritional needs.
Fish and feeding trial
Rainbow trout fry were purchased from a private hatchery and acclimated to the laboratory conditions in a 5000-L capacity glass tank, connected to a freshwater recirculating system equipped with a chiller unit to help maintain the water temperature at 15.2 °C, feeding on a commercial diet (Woosung Feed Co., Daejeon, South Korea; 50% crude protein and 13% lipid). Following the 2-week acclimation period, 25 fish (initial mean body weight, 1.11 ± 0.01 g) were randomly stocked into each 60-L rectangular glass aquarium supplied with dechlorinated/filtered freshwater using a closed recirculating system previously described (Sankian et al. 2018). Dissolved oxygen, pH, ammonia-N, and nitrite levels were measured twice a week (7.6 ± 0.2 mg/L, 7.8 ± 0.2, < 0.6 mg/L, and < 0.2 mg/ L), and photoperiod was left under natural conditions during the experiment. Each experimental diet was hand-fed to triplicate groups of fish to apparent satiation (twice daily at 09:00 and 17:00 h) for 8 weeks. The uneaten feed was siphoned out and weighed to determine net daily feed consumption. Fish were fasted for 18 h before sampling to minimize handling stress on fish.
Table of Growth performance, feed utilization efficiency, and morphological parameters of rainbow trout fed the five experimental diets for 8 weeks
Fish growth performance in terms of weight gain and specific growth rate significantly increased with increasing dietary MW level up to 14% and then declined when dietary MW levels further increased to 28%. Significantly higher protein efficiency ratio and lower feed conversion ratio were found in fish fed with diets containing MW compared to fish fed the control MW0. Myeloperoxidase activity was significantly higher in fish fed MW7 diet compared to fish fed the MW0 diet. Fish fed the MW14 and MW28 diets had significantly higher lysozyme activities than those fed the MW0 diet.
Overall, the efficacy of MW as promising alternative to fish meal in practical diets for rainbow trout fry has been proved not only in relation to growth rates and feed utilization, but also from the viewpoint of immunopotentiation effects.
Citation:
Jeong, SM., Khosravi, S., Mauliasari, I.R. et al. Dietary inclusion of mealworm (Tenebrio molitor) meal as an alternative protein source in practical diets for rainbow trout (Oncorhynchus mykiss) fry. Fish Aquatic Sci 23, 12 (2020). https://doi.org/10.1186/s41240-020-00158-7