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Open AccessArticle

Effects of Graded Dietary Inclusion Level of Full-Fat Hermetia illucens Prepupae Meal in Practical Diets for Rainbow Trout (Oncorhynchus mykiss)

1
Department of Agricultural, Food, Environmental and Animal Science, University of Udine, 33100 Udine, Italy
2
Department of Life and Environmental Sciences, Polytechnic University of Marche, 60131 Ancona, Italy
3
Department of Agriculture, Food, Environment and Forestry, University of Florence, 50144 Florence, Italy
*
Authors to whom correspondence should be addressed.
These two authors equally contributed to the study.
Animals 2019, 9(5), 251; https://doi.org/10.3390/ani9050251
Received: 18 March 2019 / Revised: 9 May 2019 / Accepted: 12 May 2019 / Published: 17 May 2019
(This article belongs to the Special Issue Insects: Alternative Protein Source for Animal Feed)
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Simple Summary

The sustainability of fish production is mainly driven by the protein source used in aquafeeds. In conventional fish feed, protein sources are mostly vegetable ingredients and fishmeal. The present study explored the potential use of full-fat Hermetia illucens prepupae meal (H) replacing 0% (H0), 25% (H25), and 50% (H50) conventional ingredients in practical diets for rainbow trout. No significant differences in growth were observed in all experimental groups, while in fish fed the H50 diet both hepatic and intestinal alterations were detected. In addition, in the same fish group, genes related to stress and immune-response were significantly up-regulated. The results obtained so far highlighted an overall physiological adaptation of fish to the dietary manipulation, suggesting an adverse effect of full-fat H at the highest inclusion level.

Abstract

This study investigated the effects of dietary inclusion levels of full-fat Hermetia illucens prepupae meal (H) on growth and gastrointestinal integrity in rainbow trout (Oncorhynchus mykiss). A 98-day study was conducted using triplicate groups of trout (initial body weight, 137 ± 10.5 g) kept in 1-m3 tanks in a flow-through well water system. Three dietary treatments were prepared: one based on fishmeal and purified protein-rich vegetable ingredients (H0), and two experimental diets including graded levels of H meal (25% and 50%, referred to as H25 and H50, respectively). At the end of the feeding trial, no differences were observed in growth performance and plasma metabolite levels, with the biometric data confirmed by the liver expression of the genes involved in somatic growth regulation (igf1 and mstn1a). In the H50 group, a three-fold up regulation of liver hsp70 was observed. An activation of the stress/immune response (il-10, tnf-α, and tlr-5) was observed in medium intestine in the H25 and H50 groups (p < 0.05) together with a villi length reduction detected through histological analyses. Liver histology and Fourier Transform Infrared Imaging (FTIRI) spectroscopy highlighted an increase in lipid deposition. These findings suggest that caution should be taken into account when 50% replacement of conventional ingredients with H is selected. View Full-Text
Keywords: black soldier fly; feed formulation; alternative proteins; growth metrics; FTIRI spectroscopy; gastrointestinal health; plasma metabolite black soldier fly; feed formulation; alternative proteins; growth metrics; FTIRI spectroscopy; gastrointestinal health; plasma metabolite
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MDPI and ACS Style

Cardinaletti, G.; Randazzo, B.; Messina, M.; Zarantoniello, M.; Giorgini, E.; Zimbelli, A.; Bruni, L.; Parisi, G.; Olivotto, I.; Tulli, F. Effects of Graded Dietary Inclusion Level of Full-Fat Hermetia illucens Prepupae Meal in Practical Diets for Rainbow Trout (Oncorhynchus mykiss). Animals 2019, 9, 251.

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