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Early performance, stress- and disease-sensitivity in rainbow trout fry (Oncorhynchus mykiss) after total dietary replacement of fish oil with rapeseed oil. Effects of EPA and DHA supplementation

Gesto, Manuel; Madsen, Lone; Andersen, Nikolaj R.; Kertaoui, Najlae El; Kestemont, Patrick; Jokumsen, Alfred and Lund, Ivar (2021) Early performance, stress- and disease-sensitivity in rainbow trout fry (Oncorhynchus mykiss) after total dietary replacement of fish oil with rapeseed oil. Effects of EPA and DHA supplementation. [Vækst, stress- og sygdoms følsomhed hos regnbueørrred yngel (Oncorhynchus mykiss) efter total udskiftning af fiskeolie med rapsolie. Effekter af tilsætning af EPA og DHA.] Aquaculture, online, pp. 1-43.

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Summary

Different vegetable oils have been investigated as potential substitutes of fish oil in aquaculture feed and several of them have proven to be successful in terms of fish growth rates, survival rates, biometric indices or feeding efficiency, even when used as the only oils in the feed. However, final fish product composition (fish whole body or fish fillet) usually reflects feed composition, and fish products from fish fed with only vegetable oils usually show a deficiency in long chain polyunsaturated fatty acids (PUFAs). The welfare and health consequences for the fish of these alterations of the fatty acid profile are not well known. In the current study, three experimental diets using super critically defatted fishmeal as well as rapeseed oil as a 100 % replacement of fish oil, and differing in essential fatty acid (eicosapentaneoid acid - EPA, docosahexaenoic acid - DHA) supplementation, were tested in rainbow trout, Oncorhynchus mykiss. The growth performance, feed conversion ratio and digestive enzyme profiles were evaluated. Further, stress-and infection-challenge experiments were performed to assess the robustness of the fish against stress and disease. The trout fry fed the experimental diets showed a different fatty acid profile than fish fed a commercial diet, with lower EPA and DHA levels but higher linolenic acid (18:3n-3) and oleic acid (18:1n-9) levels. No significant effects were found in growth performance, feed conversion ratio or digestive enzymatic activity among diets. The fish stress responsiveness (brain and plasma stress marker response) to acute and repeated stressors was in general also similar irrespective of the diet. Infection trials, however, showed a differential ability of the fish to survive upon a controlled infection with the bacterium Flavobacterium psychrophilum. Fish fed with the experimental diets displayed higher mortalities than fish fed a commercial trout fry diet. The current results highlight the need of further research on nutritional requirements to optimize the disease resilience in farmed fish. These results also demonstrate that the adaptation of the fish to new formulated feed (in this case associated to plant oil ingredients) should not be assessed solely based on the growth performance of the fish. Other aquaculture relevant welfare indicators, as disease or stress resilience, should be part of a more complete assessment of feed adequacy for fish farming purposes.


Summary translation

Adskillige planteolier er blevet undersøgt som mulige erstatninger for fiskeolie i fiskefoder og mange har vist sig succesfulde i forhold til bl.a. vækst, overlevelse og foderudnyttelse. Men produktkvaliteten kan måske være udfordret af, at fileten får et lavere indhold af de langkædede flerumættede fedtsyrer (PUFAs). Det er uvist hvorvidt dette har indflydelse på fiskesundhed og velfærd.
I dette studie blev tre forsøgsdiæter med super kritisk af-fedtet fiskemel, samt rapsolie som erstatning for fiskeolie og varierende tilsætning af essentielle fedtsyrer (eicosapentaen syre - EPA, docosahexaen syre - DHA) testet hos regnbueørred, Oncorhynchus mykiss. Der blev ikke fundet signifikante effekter blandt diæterne på hverken vækst, foderudnyttelse eller aktivitet i fordøjelsesenzymer.
Fisk fodret med de eksperimentelle diæter havde ændret fedtsyre profil i forhold til fisk på kommercielt foder, dvs. lavere EPA og DHA niveauer men højere linolen syre (18:3n-3) og olie syre (18:1n-9) niveauer. Stress respons (akut og gentagen) udtrykt ved hjerne og plasma stress markører var stort set ens for alle grupper. Derimod viste kontrollerede infektions forsøg med bakterien Flavobacterium psychrophilum forskellig overlevelse afhængig af fodertype. Således udløste de eksperimentelle diæter højere dødeligheder end de kommercielle. Resultaterne underbygger således behovet for yderligere ernærings studier til optimering af sygdoms resistens hos opdræts fisk. Resultaterne viste også, at fiske respons til nye diæter, som her planteolier, skal ikke alene baseres på vækstpotentialer, men også velfærds indikatorer, som sygdoms og stress håndtering, bør indgå i en overordnet vurdering af nye fodertyper til akvakultur.

EPrint Type:Journal paper
Keywords:aquaculture; fish nutrition; fish health; fish welfare; trout; vegetable oil; fish disease
Agrovoc keywords:
Language
Value
URI
English
UNSPECIFIED
UNSPECIFIED
Subjects: Animal husbandry > Feeding and growth
Animal husbandry > Health and welfare
Research affiliation: Denmark > Organic RDD 2 > RobustFish
DOI:10.1016/j.aquaculture.2021.736446
Deposited By: Jokumsen, Senior Advisory Scientist Alfred
ID Code:39139
Deposited On:08 Feb 2021 09:20
Last Modified:11 May 2021 10:06
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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