Replacing Dietary Fish Oil with Vegetable Oil Blends in Female Rainbow Trout Brood Stock Does Not Affect Breeding Quality

Abstract

To determine the effects of replacing fish oil (FO) with a mixture of vegetable oils (VO) in plant protein‐rich diets on reproductive performance, the fatty acid profile of embryos as well as health indices of female rainbow trout (Oncorhynchus mykiss) brooders (initial mean body weight, 1.8 ± 0.1 kg), a 3‐month feeding trial was conducted. Four isoproteic (ca. 42%) and isoenergetic (ca. 20 MJ/kg) diets were formulated in which 50% (FO50/VO50), 75% (FO25/VO75), and 100% (VO100) of FO were replaced by a mixture of VO, whereas the control diet (FO100) was prepared with FO as the major source of lipid. Fish fed the VO100 had the lowest fertilization (73.0 ± 2.5%), survival at eyed‐embryo stage (62.5 ± 5.0%), and hatching rate (56.0 ± 4.7%) rates. Brood fish fed the FO50/VO50, FO25/VO50, and VO100 diets had higher levels of saturated and monounsaturated fatty acids in embryos in comparison with fish fed FO100 diet. The levels of docosahexaenoic acid of embryos gradually decreased during embryogenesis in all treatments, whereas the concentrations of eicosapentaenoic acid was greatly increased at hatching day (35 days after spawning). Regarding serum biochemical parameters, fish fed the VO100 diet had the highest serum glucose, cholesterol, and low‐density lipoprotein levels. The results of the current study revealed that replacement of dietary FO with a mixture of VO up to 75% did not have any adverse effects on reproductive performance and health indices of O. mykiss females.

The influence of dietary fish oil replacement with mixture of vegetable oils on reproductive performance, immune responses and dynamic of fatty acids during embryogenesis in Oncorhynchus mykiss

“…The proportions of SFA increased in embryos during the day 20 and the hatching day (day 35; Table ). In agreement with our results, several studies in other cold water fish species such as Clupea harengus (Tocher, ), Salmo salar (Murzina et al, ) and O. mykiss (Agh et al, ; Noori et al, ) documented a proportional increase in SFA during embryogenesis. The augmentation of the SFA biosynthesis in de novo pathway may result in an increase in the SFA concentrations in embryos, which could provide their energy requirement for hatching (Cejas et al, ; Murzina et al, ; Sargent, Tocher, & Bell, ).…”

“…In this sense, Lazzarotto et al () reported female brooders of O. mykiss fed only vegetal‐based feeds containing blends of VO over a 3‐year reproduction period had successful larvae production by biosynthesizing LC‐PUFA from their precursors in the feed and incorporating them into the ova. Furthermore, previous studies in our laboratory also demonstrated substitution of dietary FO up to 75% with different mixture of VO in PP‐rich diets supported successful reproduction performance in O. mykiss females (Agh, Jafari, Jalili, Noori, & Mozanzadeh, ; Noori et al, ). In contrast to our previous research, in this study we increased the proportions of linseed and sunflower oils as good sources of α‐linolenic (ALA) and linoleic (LNA) acids in the mixture of VO for increasing the content of PUFA in the experimental diets.…”

“…Moreover, in this study the inclusion levels and proportions of linseed and sunflower oils, which are good sources of ALA and LNA, respectively, were increased in the blends of VO that resulted in high levels of ALA and LNA as well as PUFA in the experimental diets (Table ). This modification in the VO mixture could be resulted in better reproductive performance in fish fed the 100VO diet compared to our previous studies (Agh et al, ; Noori et al, ). It seems that the differences in FA profile and the ratios between FA classes of feeds in this study as a consequence of different mixture of VO could be accounted for such discrepancies in these results.…”

“…In this sense, it has been confirmed that high resistance of O. mykiss to PP‐rich diets and also their capacity to synthesize LC‐PUFA from their precursors in diet (Gregory, Collins, Tocher, James, & Turchini, ) resulted in twice successful spawning in spawners fed plant‐based diets in a three‐year breeding cycle (Lazzarotto et al, ). Our previous studies also demonstrated replacement of FO with VO blends in diet at 75% level did not influence reproduction in female O. mykiss , but higher substitution level (100%) reduced reproductive efficiency in this species (Agh et al, ; Noori et al, ). Moreover, in this study the inclusion levels and proportions of linseed and sunflower oils, which are good sources of ALA and LNA, respectively, were increased in the blends of VO that resulted in high levels of ALA and LNA as well as PUFA in the experimental diets (Table ).…”

“…For monitoring embryo development, fertilized eggs of each brooder were placed in an incubation tray (3,570 ± 140 eggs/tray). The average weigh and diameter of eggs, fertilization and hatching rates of eggs as well as survival rate of progeny were determined as described by Agh et al ().…”