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Epigenetics. © INRA, INRA

Livestock epigenetics: laying the foundation for future benefits

Aquaculture: conditioning fish to subsist on more sustainable feeds

Several studies by INRA scientists have shown that fish can be conditioned during early developmental stages to consume sustainable food resources, such as those made from plant matter or those containing high levels of carbohydrates. This form of dietary conditioning results from the modified expression of certain genes, possibly as a result of epigenetic tagging.

By Pascale Mollier, translated by Jessica Pearce
Updated on 07/10/2014
Published on 05/22/2014

Brown trout alevin.. © INRA, MARIE Didier
Brown trout alevin. © INRA, MARIE Didier

Dietary conditioning experiments have yielded results suggesting that fish farms may be able to use more sustainable feeds in the future. Indeed, the current practice of using fishmeal produced from pelagic species may ultimately end up depleting marine fisheries, especially since the aquaculture industry has been growing over the past two decades. In 2010, 50% of the aquatic organisms consumed by humans were produced by aquaculture.

Using results obtained in mammals as a springboard, INRA’s NUMEA research unit (1), located in St-Pee-sur-Nivelle, has developed two techniques that can be used to condition trout to consume alternative feeds.

Turning farmed fish into “herbivores”

The unit’s research has shown that trout have a dietary “memory.” That is to say, animals fed plant-based foods at the alevin stage (2) have a much easier time dealing with plant-based foods as adults. In one study, conditioned animals had a 42% higher growth rate and processed plant-based feed 18% more efficiently than control animals; their food intake was also 30% higher. “These findings are very encouraging,” comments Stéphane Panserat, NUMEA’s research director. He continues, “However, we need more complementary studies to test the persistence and repeatability of this positive effect. We also need to explore the mechanisms involved in the ‘reprogramming’ process, which seems to be partially epigenetic in origin.”

Helping farmed fish use dietary carbohydrates more efficiently

The zebrafish is native to India; the species is a popular aquarium fish and a common study organism.. © INRA, MAITRE Christophe
The zebrafish is native to India; the species is a popular aquarium fish and a common study organism. © INRA, MAITRE Christophe

Carbohydrates are an abundant, relatively inexpensive energy source that could be used in fish farming. However, trout have a hard time metabolizing glucose. When the researchers fed trout alevins a high-carbohydrate diet, they found that enzymes that break down carbohydrates remained at high levels in adult fish. Panserat explains, “Now we want to go beyond just looking at the breakdown of glucose. We want to see if we can increase how well the fish’s metabolic system exploits this sugar. To do this, we are currently injecting very small quantities of glucose into the eggs of zebrafish (Danio rerio) (3), a model organism. We have managed to significantly increase glucose concentrations in the eggs, by a factor of 40, without causing any harm to the larvae, and we have also shown that, under certain conditions, several genes involved in carbohydrate metabolism are expressed differently at the larval stage. Unfortunately, in the case of many genes, this effect doesn’t last until the juvenile stage.” The researchers are currently conducting experiments in which they expose animals to high levels of carbohydrates and are modulating such factors as carbohydrate type and the timing and length of exposure. The goal is to permanently modify carbohydrate metabolism in zebrafish (3) and trout (4).  

“Our results show that dietary conditioning is possible in trout,” Panserat concludes. He continues, “Other recent work shows that it may also be possible in other fish species, such as the European seabass and the gilthead sea bream. However, if we want to use dietary conditioning to get farmed fish to consume alternative resources, we need to understand the mechanisms at work, and the epigenome is likely one of the major players.”

(1) UR1067 NUMEA Joint Research Unit for Nutrition, Metabolism and Aquaculture

(2) Alevins received a plant-based diet for three weeks after they hatched. They were then given a standard diet (fishmeal made of marine species) for a period of seven months before once again receiving a plant-based diet for 25 days.

(3) Work done in collaboration with the University of Faro, Portugal.

(4) The European programme ARRAINA (Advanced Research Initiatives for Nutrition and Aquaculture).

Scientific contact(s):

Associated Division(s):
Animal Physiology and Livestock Systems
Associated Centre(s):


- Geurden, I., Borchert, P., Balasubramanian, M. N., Schrama, J. W., Dupont-Nivet, M., Quillet, E., Kaushik, S. J., Panserat, S. and Médale, F. (2013). The positive impact of the early-feeding of a plant-based diet on its future acceptance and utilisation in rainbow trout. PLoS ONE 8, e83162.

- Rocha, F., Dias, J., Engrola, S., Gavaia, P., Geurden, I., Dinis, M. T. and Panserat, S. (2013). Glucose overload in yolk has little effects on the long term modulation of carbohydrate metabolic genes in zebrafish (Danio rerio). J. Exp. Biol. 217 : 1139-1149.

For more information

Article on the ARRAINA programme (Advanced Research Initiatives for Aquaculture and Nutrition)