Aquaculture

Selective breeding alters nutritional needs of farmed fish à¢â‚¬â€œ a model integrating breeding and fish nutrition to support fish welfare

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Abstract

Objective of this study was to develop and demonstrate a methodology to predict changes in dietary requirements of farmed fish when fish traits are improved by selective breeding (Kause et al. 2026; Aquaculture 2026: 743171). Feed whose composition matches nutritional requirements of fish is fundamental to improve resource efficiency, product quality, fish health and welfare. Genetic improvements in growth, fillet percentage, lipid percentage, visceral waste percentage, and feed conversion ratio (FCR, feed intake / weight gain) are expected to modify fishes' nutritional requirements, and hence the required optimal feed composition. We first derived 'traits-to-feed' equations that directly estimate the required changes in feed formulation from measured trait changes, bypassing the traditional estimation of nutritional requirements by experimental dose-response trials. We applied the model to determine changes in optimal feed phosphorus (P) which showed that the effect of changes in body composition (fillet%, viscera%) on digestible P inclusion level is modest and linear. For instance, a huge change in fillet% from 60 to 70% leads to only a small decrease in dietary P from 0.74% to 0.65%. In contrast, the effects of FCR on required digestible P levels are strong and highly non-linear. An improvement in FCR from 1.5 to 0.5 increases dietary P from 0.47% to 1.4%. We then estimated genetic changes between years 1993 and 2016 in growth, FCR, fillet% and viscera% using a multitrait animal model from the data with over 547,246 individuals in 8 generations of the Finnish national breeding programme for rainbow trout. The genetic trends showed that FCR has genetically improved from 1.34 to 1.14, at a rate of 1.74% per generation, while fillet% has increased from 64.7% to 65.3%, and viscera% has decreased from 11.1% to 10.7%. When applied to the genetic trends, the 'traits-to-feed' equations predict that the required digestible P levels for the selectively bred rainbow trout has increased by 0.08752 %-points due to their improved FCR, and less so due to the changes in fillet% and viscera%. In fish, phosphorus is essential for the development of bones and cells, and during the last decades phosphorus in aquafeeds has been reduced to limit nutritional loading to environment. When the estimated genetic trends were extended into the future, the predicted digestible phosphorus is expected to be further increased, from 0.6653% in 2016 (i.e., 0.94% on total P basis) to 0.8517% in 2050. This is a 28.0% increase. To conclude, the developed equations can be used to predict changes in the dietary requirements under selective breeding, and care must be taken not to reduce the dietary phosphorus levels of feeds too much. The equations integrate quantitative genetics and fish nutrition under one united predictive framework, and they are applicable to other species.

Keywords: 2026

How to Cite:

Kause, A., Soares, F. & Silva, T., (2026) “Selective breeding alters nutritional needs of farmed fish à¢â‚¬â€œ a model integrating breeding and fish nutrition to support fish welfare”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2281175. doi: https://doi.org/10.31274/wcgalp.23453

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