Long-term dietary replacement of fishmeal and fish oil in diets for rainbow trout (Oncorhynchus mykiss): Effects on growth, whole body fatty acids and intestinal and hepatic gene expression

Abstract

The effects of replacing fishmeal and fish oil with a plant-based diet were studied in juvenile (10g) and ongrowing (250-350g) rainbow trout from first-feeding. Feed-related differences in the intestinal and hepatic transcriptome were examined in juveniles after 7 months of feeding at 7°C. Based on microarray results obtained for juveniles, the expression of selected genes related to lipid, cholesterol and energy metabolisms, was assessed by RT-qPCR in ongrowing trout after 6 additional months of feeding at 17°C. Plasma glucose and cholesterol, lipid content and fatty acid profile of whole body were analyzed at both stages. After 7 months at 7°C, all juveniles reached the same body weight (10g), while at 13 months ongrowing fish fed the totally plant-based diet exhibited lower body weight (234 vs 330-337g). Body lipid content was higher in juveniles fed the totally plant-based diet (13.2 vs 9.4–9.9%), and plasma cholesterol was about 2-times lower in trout fed the plant-based diets at both stages. Fatty acid profile mirrored that of the respective diet, with low proportions of long-chain n-3 polyunsaturated fatty acids in fish fed plant-based diets. Genes involved in protein catabolism, carbohydrate metabolism and trafficking were down-regulated in the intestines of juveniles fed the plant-based diets. This was not true for ongrowing fish. Genes involved in lipid and cholesterol metabolisms were up-regulated in the livers of fish fed plant-based diets for both stages. In this study, feeding trout a totally plant-based diet from first-feeding affect a relatively low proportion of metabolism-related genes. In the longer term, when fish were reared at a higher temperature, only some of these changes were maintained (i.e. up-regulation of lipid/cholesterol metabolism). Although the plant-based diets tested in this study had no major deficiencies, small adjustments in the feed-formula are needed to further optimize growth performance while sparing marine resources.

Intestinal microbiota in rainbow trout,Oncorhynchus mykiss, fed diets with different levels of fish-based and plant ingredients: A correlative approach with some plasma metabolites

“…After 13 months of feeding without fish meal and fish oil, the mean body mass of the “plant” group P was significantly lower than that of the other two groups (Lazzarotto et al., ).…”

“…At the end of this second period of feeding, the fish were fasted for 48 hr before sampling as described previously (Lazzarotto et al., ). Five trout were randomly sampled from each tank (15 fish per experimental group), weighed and euthanized, before collecting plasma for biochemical and metabolomic analyses.…”

“…Fish feed producers have to replace as much as possible the feed ingredients coming from marine resources by alternative sources such as environment‐friendly crops, which are reliable in terms of economic and ecological sustainability. Long‐term experiments demonstrated that rainbow trout ( Oncorhynchus mykiss ) could grow and breed without supply of marine feed ingredients (Lazzarotto et al., ), although this total replacement of fish meal and fish oil affected to some extent the lipid/cholesterol metabolism and the body growth of trout (Lazzarotto, Médale, Larroquet, & Corraze, ).…”

Bovine plasma protein as an alternative protein source in extruded aquafeeds forPiaractus mesopotamicus(pacú) at two fattening stages

“…On the other hand, FM replacements in feedstuffs are known to affect the metabolic response at different levels, including gene expression. Lazzarotto, Médale, Larroquet, and Corraze () observed that hepatic genes involved in long‐chain polyunsaturated fatty acids bioconversion and cholesterol biosynthesis were up‐regulated when fish meal was completely replaced by a plant‐based diet. Although our results suggest stimulation of the lipogenic pathways in P. mesopotamicus fed with the BPPD, further studies are needed to elucidate the mechanistic pathways causing such effect.…”

Using systems thinking and open innovation to strengthen aquaculture policy for the United Nations Sustainable Development Goals

“…Research continues to investigate the successful substitution of fishmeal with alternative (preferably vegetable) diets in fish feeds. Success in this research field would allow aquaculture to increase its overall fish production without threatening wild fish stocks (Lazzarotto et al , ) and help counter debates on unsustainable sources of feed ingredients.…”