Abstract
A 12-week feeding trial was designed to evaluate the effect of total replacement of fish oil (FO) with terrestrial alternative oils on growth, feed utilization, body composition, hematological parameters, and fillet fatty acid profile of mandarin fish juveniles. Four iso-nitrogenous (56% crude protein) and iso-lipidic (13% crude lipid) practical diets were formulated. A control diet contained 6% FO and three other experimental diets were prepared by replacing FO with linseed oil, soybean oil, and lard (designed as FO, LO, SO, and lard, respectively). Each diet was randomly allocated to triplicate groups of 25 fish (1.8 ± 0.03 g/fish) in a circular tank. Complete replacement of FO by three tested alternative oils had no remarkable impact on growth performance, feed utilization efficiency, and morphological and hematological parameters of juvenile mandarin fish. However, daily feed intake was found to be significantly higher for fish fed the SO diet compared with those fed the FO and LO diets. Fish fed LO and SO diets exhibited significantly higher levels of the whole body lipid compared to fish fed diet containing FO. Fillet fatty acid composition reflected dietary fatty acid profile. The highest level of α-linolenic acid, linoleic acid, and oleic acid was observed in fish fillet fed LO, SO, and lard, respectively. Although the eicosapentaenoic acid level of fish fillet fed diet FO was higher than other treatments, no significant difference was found in docosahexaenoic acid content among all dietary groups. The results of the present study clearly demonstrate that the complete replacement of FO in mandarin fish diets is achievable. These findings are useful in dietary formulation to reduce feed costs without compromising mandarin fish growth.
Highlights
Feed ingredients of marine origin such as fish meal (FM) and fish oil (FO) have been extensively used as the main protein and lipid sources in the aquafeeds
Fish oil is popular in aquafeed industry because of its high proportions of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) that play an important role in supporting normal growth, health, and nutritional quality of farmed aquatic animals (Turchini et al 2011b)
The findings of the present study showed that FO in a practical diet with 13% lipid for juvenile mandarin fish can be completely replaced by linseed oil (LO), soybean oil (SO), or lard without markedly compromising growth performance and feed efficiency
Summary
Feed ingredients of marine origin such as fish meal (FM) and fish oil (FO) have been extensively used as the main protein and lipid sources in the aquafeeds. A review of previous experiments with freshwater species such as Murray cod, Maccullochella peelii peelii (Turchini et al 2011a); pikeperch, Sander lucioperca (L.) (Kowalska et al 2012); snakehead, Channa striatus (Aliyu-Paiko and Hashim 2012); darkbarbel catfish, Pelteobagrus vachelli (Jiang et al 2013); Nile tilapia, Oreochromis niloticus (Peng et al 2015; Apraku et al 2017); gibel carp, Carassius auratus gibelio (Zhou et al 2016); silver catfish, Rhamdia quelen (Lazzari et al 2016); and rainbow trout, Oncorhynchus mykiss (Gause and Trushenski 2013; Yıldız et al 2018); has shown that it is possible to replace FO by single or a mixture of terrestrial oils (both vegetable and animal oils) without compromising growth or feed efficiencies
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