A well-known challenge
European fish farmers have to face a competitive market where environmental concerns are now at the center of consumer choices. The feed distributed to fish is at core of sustainable development of aquaculture. On the one hand, feed is the first item of expenditure, and can represent up to 70% of the costs of producers (Besson et al., 2016). On the other hand, feeds contribute to the exploitation of fishery resources and to degrading the environment around the farms, and are the main contributor to the global environmental impact of aquaculture in Life Cycle Analyses. The sustainable development of fish farming therefore depends on its ability to use less feed. One of the key levers to meet this objective is to improve the feed conversion ratio (FCR) of farmed fish through selective breeding (de Verdal et al., 2018). FCR represents the ability of fish to convert the feed distributed into fish biomass.
The killer question
Including feed efficiency as a trait in fish breeding programs, an accessible grail or a wonderful myth?
We will review the latest results obtained on European sea bass (Besson et al., 2019, Rodde et al., 2021), gilthead seabream (Besson et al., 2022), rainbow trout, and Nile tilapia (de Verdal et al., 2022), in order to identify successes and remaining issues in the genetic improvement of feed efficiency, and to identify future directions.
The present strategies
During the past two decades, a huge effort has been deployed to tackle a simple but very hard problem: how to accurately measure feed intake of individual fish? Individual phenotypes are indeed the key for efficient genetic improvement of feed efficiency.
We will see how this question was either targeted (radio-opaque glass beads, isolated fish feed intake, chemical markers, video recording) or circumvented (screening of putative correlated indirect traits, including growth rates, fasting-tolerance, metabolic rate, behaviour) in different projects. Genetic variation, putative efficacy of pedigree and genomic-based selective breeding for feed efficiency through these strategies will be compared and discussed.
Which future opportunities ?
Prospects of improvement of feed efficiency with alternative methods to estimate feed intake including stable-isotopes strategies, or artificial intelligence-based feeding behaviour tracking (including fish recognition and pellets detection), will be exposed and discussed.
Acknowledgements
This project was supported by projects AQUAEXCEL2020, EMBRIC, PerformFISH and AquaIMPACT from the EU Horizon 2020 Framework programme and projects DADA-EAT and SELFIE, from the European Maritime and Fisheries Fund (EMFF) and the French government.
References
Besson, Mathieu, et al. "Influence of water temperature on the economic value of growth rate in fish farming: the case of sea bass (Dicentrarchus labrax) cage farming in the Mediterranean." Aquaculture 462 (2016): 47-55.
Besson, Mathieu, et al. "Potential for genomic selection on feed efficiency in gilthead sea bream (Sparus aurata), based on individual feed conversion ratio, carcass and lipid traits." (2022).
Besson, Mathieu, et al. "Combining individual phenotypes of feed intake with genomic data to improve feed efficiency in sea bass." Frontiers in genetics 10 (2019): 219.
Rodde, Charles, et al. "An investigation of links between metabolic rate and feed efficiency in European sea bass Dicentrarchus labrax." Journal of Animal Science 99.6 (2021): skab152.
de Verdal, Hugues, et al. "Improving feed efficiency in fish using selective breeding: a review." Reviews in Aquaculture 10.4 (2018): 833-851.
de Verdal, Hugues, et al. "Impact of a divergent selective breeding programme on individual feed conversion ratio in Nile tilapia Oreochromis niloticus measured in groups by video-recording." Aquaculture 548 (2022): 737572.