Influence of black soldier fly (Hermetia illucens) larvae oil on growth performance, body composition, tissue fatty acid composition and lipid deposition in juvenile Jian carp (Cyprinus carpio var. Jian)
Introduction
As one of the major nutrients, dietary lipids play important roles in fish nutrition. Lipids are important because of its many advantages such as being a potent energy source, a component of cellular membranes, and promoting absorption of lipophilic nutrients (Halver, 2002). Many previous studies of fish have highlighted the importance of fish oil as a major constituent in diets. However, due to increasing costs and limited supplies of global fish oil (Tacon and Metian, 2008), it was currently of great urgency for the aquafeed industry to investigate the possibilities of alternative dietary lipid sources. The black soldier fly (Hermetia illucens) has become a popular bio-recycling organism in the world due to its detritivorous nature (Bondari and Sheppard, 1981, Diener et al., 2009, Sheppard et al., 1994, Stamer et al., 2007, Zheng et al., 2012). It has been reported that black soldier fly larvae contain about 42% protein and 35% fat (Sheppard et al., 1994) and have been demonstrated to be a good alternative feed in fish production (St-Hilaire et al., 2007), with the potential to replace fish meal and fish oil as source of animal feed lipids. Previously, many research of the black soldier fly larvae meal have shown it as an alternative protein source for feed purposes (Newton et al., 2005, Sealey et al., 2011, St-Hilaire et al., 2007, Zhang et al., 2014). Black soldier fly larvae oil (BSO) is a byproduct of black soldier fly larvae meal production. And applied research is now needed to fill the knowledge gaps by utilizing the oil of black soldier fly in fish diets. The fatty acid profiles of black soldier fly larvae show that linoleic acid (LNA, 18:2n-6; concentration (3.6%–4.5%) is much greater than that of α-linolenic acid (ALA, 18:3n-3; 0.08%–0.74%), similar to many plant oils (such as soybean oil and sunflower oil), and rich in medium-chain fatty acids (MCFA) with lauric acid (LA, 12:0) representing 21.4%–49.3% of total fatty acids, which is similar to coconut oil (Tran et al., 2015). There are many studies reported that applying a certain proportional soybean oil (Deng et al., 2014, Emre et al., 2015, Peng et al., 2008), sunflower seed oil (Bell et al., 1996, Bransden et al., 2003, Wijekoon et al., 2014) or coconut oil (Fontagné et al., 2000, Legendre et al., 1995, Luo et al., 2014) to fish feed did not negatively affect growth.
The role of MCFA as energy-yielding substrates has been largely invested in terrestrial animals (Aurousseau et al., 1989, Bozzolo et al., 1993). In mammals, MCFA have been reported to do not need carnitine palmitoyltransferase-1 (CPT-1) mediated transport to enter mitochondria which may accelerate their oxidation. Also in fish, dietary inclusion of MCFA resulted in decreased fat deposition in the muscle, liver and intra-peritoneal fat with similar or improved growth rates (Nakagawa and Kimura, 1993). Negative effects on the efficiency of energy or lipid retention were also seen in Atlantic salmon (Salmo salar) fed purified MCFA (Nordrum et al., 2003) and in polka-dot grouper fed CO, suggesting high levels of C12-β-oxidation (Williams et al., 2006). By comparison, Figueiredo-Silva et al. (2012) revealed high C12 retention from CO, with C12 representing over 20% of total body fatty acids compared to < 1% in trout fed FO. Furthermore, according to a previous study in our lab, the diet with 0.5% ethyl laurate could depress juvenile Pagrus major lipid accumulation (Ji et al., 2005).
Jian carp (Cyprinus carpio var. Jian) is one of the economically important freshwater-cultured fish. In China, the production of Jian carp presents almost 50% of that of common carp every year (Zhou et al., 2008). Since its high meat content, deliciousness, high nutritional value, and cheap price, Jian carp is popular with consumers and the market demand is great.
Therefore, the aim of this study was to estimate the BSO in the diet of Jian carp. We investigated the effects of BSO on growth performance, feed utilization, body fatty acid profiles, serum biochemical parameters, and lipid metabolism in Jian carp, in order to provide reference information for the culture of carp using BSO as lipid source.
Section snippets
Experimental diets
Five experimental diets were formulated to be isonitrogenous and isolipidic with approximately 34% crude protein, 7% crude lipid in the diets (National Research Council, 1993). Black soldier fly larvae provided by Jiemu Co. Ltd. (Xi'an, Shaanxi Province, China) and the black soldier fly larvae oil was obtained by cold-press technique added to the diets to replace soybean oil (SO). The replacement levels were 25% (BSO25), 50% (BSO50), 75% (BSO75), and 100% (BSO100), respectively. All diets were
Diets composition
The five experimental diets had similar total lipid (6.23%–6.67%) content, crude protein (30.42%–30.79%) content and moisture (11.09%–11.55%) content (P > 0.05, Table 1), but differed greatly in their fatty acid profile (Table 2). Black soldier fly larvae oil contained high concentration (36.37%) of lauric acid (LA, 12:0), therefore, graded increases in this fatty acid and consequently total saturated fatty acids (SFA) were noticed in the resulting BSO diets with each increment of inclusion
Discussion
Black soldier fly larvae have been reported to contain 26% lipids (Tran et al., 2015) with lauric acid as a prominent fatty acid (Leong et al., 2016). However, research on the application of BSO was scarce in aquafeed. In the present study, both all-soybean oil and black soldier oil diets were equally consumed by Jian carp throughout the 59 days experiment, indicating that voluntary feed intake was not affected by substitution of soybean oil by black soldier fly larva oil (BSO), even at the
Acknowledgement
The present study was supported by Ankang Fisheries Experimental and Demonstration Station of Northwest A & F University (Z222020001). The authors wish to express thanks to Shisheng Liu, Haojie Chen and Zhou Yang for their assistance in the process.
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