Effects of inclusion of offal meal and oil extracted from giant beetle worm, Zophobas morio on growth performance, body composition, and hepato- visceral indices in juvenile rainbow trout Oncorhynchus mykiss

Document Type : Research Paper

Authors

1 Department of Fisheries, Faculty of Animals Sciences and Fisheries, Sari Agricultural Sciences and Natural Resource University, Sari, Mazandaran, Iran

2 Gorgan Inland Waters Aquatic Resources Research Center, Gharesu Center, Golestan, Iran

Abstract

Introduction: Due to the rapid growth of the human population and increasing standard of living, there is a rising demand for seafood. Aquaculture relies heavily on the consistent supply of fishmeal (FM) and fish oil, major components in commercial fish feeds. Due to the current scarcity of FM, alternative protein sources that provide similar nutritional benefits to FM and fish oil have been explored extensively. Insect meals will be a suitable alternative as the nutritional components, which are more similar to FM. In this study, the effects of replacing different levels of superworm (Zophobas morio) offal meal and extracted oil instead of fish meal and oil were investigated on growth performance, feed conversion ratio, body composition, and hepato-visceral indices in juvenile rainbow trout (Oncorhynchus mykiss).
Material and methods: Fish (n = 420, initial average weight of 12 ± 0.2 g) were randomly distributed to 21 polyethylene circular tanks with a capacity of 250 L for 56 days. Seven isonitrogenous (41.5%) and isolipidic (16%) diets were formulated where the FM and fish oil of the control diet was replaced by Z. morio offal meal at 25, 50, and 75% instead of FM, and Z. morio oil was replaced at 25, 50 and 100% by fish oil. At the end of the trial, growth performance, feeding parameters, body composition, and hepato-visceral indices were calculated in different treatments. For data analysis, One-Way ANOVA and Duncan's multiple range comparison tests were performed at the significant level of P<0.05.
Results and discussion: According to the results, final weight, specific growth rate, and feed conversion ratio of fish in the meal and oil replacement treatments showed no significant differences compared to the control group (P>0.05). Body protein contents did not significantly differ between the groups fed with offal meal and superworm oil compared to the control group (P>0.05). Body lipid significantly increased by elevating meal replacement levels compared to the control group (P>0.05), however, no differences were observed by oil replacement levels compared to the control group (P>0.05). Liver index in fish fed at levels higher than 25% meal replacement significantly increased (P<0.05), but no differences were observed in oil replacements compared to the control (P>0.05). The visceral index showed no differences in meal replacement treatments (P<0.05), however, its lowest value was observed in 25 and 50% oil replacements.
Conclusion: Based on the results, replacing 25% of offal meal and up to 50% of superworm oil in the trout diet seems reasonable.

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