Integrated alternative approaches to select feed-efficient rainbow trout families to enhance the plant protein utilization

Abstract

Improving feed utilization efficiency is a challenge in aquaculture. Therefore, we developed an indirect benchmark to use in selecting trout for improved efficiency of feed utilization on plant protein (soy)-based diets, with the long-term goal of reducing the cost of commercial trout production. We used a four-part integrative approach to identify feed efficient individuals among 1595 fish coming from 12 genetically selected families by establishing the phenotypic relationship between feed conversion ratio (FCR) and body weight variations using compensatory feeding regimes. Additionally, we examined the nutritional composition of fish filet for each efficiency phenotype during the compensatory regimen. Our findings showed that the fish with the lowest weight loss during a feed deprivation period and the highest weight gain during the refeeding period (FD-/RF +) demonstrated the lowest FCR (FCR = 0.99) and consisted of individuals from several lines. This finding confirms the possibility of improving feed efficiency in mixed lines. Although feeding period has an effect on nutritional composition of fillet, such selection criteria did not show an effect on groups. Overall, successful selection for the improvement of feed efficiency will have a broad application to commercial fish selective breeding programs, leading to increased aquaculture sustainability in the long run.

Figure 1

Experimental outline schematic. FD Feed deprivation; RF Re-feeding; TGC Thermal growth coefficient. Illustration Created with BioRender.com.

Figure 2

Body weight performance during the first feeding challenge 340–448 pf. FD- and FD + refer to fish with small and high weight loss during a feed deprivation period, RF- and RF + refer to small and high weight gain during a refeeding time. Individuals within the limits of the dotted line (at the center) were not classified with this criterion. Performance is shown as residual values computed through multiple linear regression of TGC.

Figure 3

Growth over the entire experimental period.

Figure 4

(A) Following the first phase of experiment, FCR was recorded between days 478 and 550 dpf. (B) Growth and feed intake parameters for the four groups.

Figure 5

(A) body weight performance during the second feeding challenge 550–637 dpf. FD- and FD + refer to fish with small and high weight loss during a feed deprivation period, RF- and RF + refer to small and high weight gain during a refeeding time. Performance is shown as residual values computed through multiple linear regression of TGC. Fluorescent green asterisks represent the individuals with similar performance during the two feeding challenges. (B) Distribution of individuals with similar performance in two challenges among families.

Figure 6

Moisture, protein and fat content of muscle during the second feeding challenge.