Feed efficiency of rainbow trout can be improved through selection: Different genetic potential on alternative diets1

Abstract

To assess the genetic potential for selection of increased feed efficiency in rainbow trout (Oncorhynchus mykiss), we estimated the heritabilities and correlations for BW, daily weight gain (DG), and daily feed intake (DFI). Body weight was recorded 5 times, and DG and DFI 3 times during a feeding trial lasting 22 mo. To test the hypothesis that phenotypic and genetic parameters were influenced by a nutritional environment, fish were fed either a modern normal protein diet (NP, 40 to 45% protein and 30 to 33% lipid) or an alternative high protein diet (HP, 50 to 56% protein, 20 to 24% lipid) in a split-family design. Results showed that there were no large differences in heritabilities between the diets. Average heritability for DFI over both diets and different fish ages was low (average h2 = 0.10), indicating that modest genetic changes in response to selection can be obtained. Average heritabilities for BW and DG over both diets and different fish ages were 0.28 and 0.33, respectively. The NP diet enabled fish to express a wide range of BW, as shown by the increased coefficients of phenotypic variation for BW. Fish fed the HP diet showed increased phenotypic variation for DFI in > 750-g fish. On the NP diet, genetic correlations of DFI with DG and BW were very strong for 750- to 2,000-g fish. In contrast, on the HP diet, the respective correlations were moderate to low, revealing more genetic potential to change growth and feed intake simultaneously in opposite directions. An analysis of the predicted selection responses showed that selection solely for high DG improved feed efficiency as a correlated genetic response. Simultaneous selection for high DG and reduced DFI, in turn, may increase genetic gain in feed efficiency by a factor of 1.2 compared with selection solely for DG. However, variation for growth and feed intake and the relationships between these traits were different in different nutritional environments, leading to divergent genetic responses on the alternative diets.

Genetic variability in residual feed intake in rainbow trout clones and testing of indirect selection criteria (Open Access publication)

“…However, because of the genetic Selection for residual feed intake in fish structure of our population (genetically identical fish and a single dam common to all individuals), this value cannot be compared with data found in the literature. Few studies have assessed genetic variability of feed efficiency in fish [15,21,23,33,36,39]. Among these only one study gives precise differences in RFI among families and individuals [35].…”

“…However, the effect of growth selection on feed efficiency is disputed. While Kause et al [21] have found that rapid growth in rainbow trout (Oncorhynchus mykiss) is related to high feed efficiency, Mambrini et al [27] have not detected any improvement in feed efficiency when selecting brown trout (Salmo trutta) for growth gain. Hence at least in brown trout, selection on growth does not necessarily lead to improvement in feed efficiency.…”

Different Dietary Levels of Protein to Lipid Ratio Affected Digestive Efficiency, Skeletal Growth, and Muscle Protein in Rainbow Trout Families

“…It was purely intended to act as a challenge environment to optimising the genetic response of traits such as protein and growth efficiency in salmonids [21,22,27]. However, as a long-term study, it has enabled us to investigate the effect of dietary protein on skeletal growth (length), which is important knowledge for future production of fish with high growth performance quality [32] as well as for future growth study in natural ecosystems where protein deposition is the main cause [12].…”

Breeding salmonids for feed efficiency in current fishmeal and future plant-based diet environments

“…To calculate genetic response in FE, mean FE was first calculated for each diet from the data, i.e., before selection. Then, genetic responses to selection were calculated for DG and DFI, and the new mean FE was calculated from these [22].…”

“…Breeding programmes exist for all major farmed carnivorous fish species, and have achieved improvements in growth, feed efficiency, disease resistance and product quality traits [12]. Improved feed efficiency in particular is a goal of most fish breeding programmes, but genetic parameter estimates for feed consumption and efficiency are rare [21,22,24,42]. This is because recording methods for individual fish feed intake have only recently been implemented in large-scale genetics research [21,22,42]; thus no current breeding programmes select directly for feed efficiency.…”