Testing fat content or feeding behaviour as indirect selection criteria for feed efficiency using trout isogenic lines

International audiencePhenotyping individual feed intake through direct measurements remains complex in fish, andone way to overcome this challenge is to find indirect criteria for estimating feed efficiency.This study investigated the correlations between fish residual feed intake (RFI) and fat contentor the number of feed demands in ten isogenic lines of rainbow trout. We found positivecorrelations between RFI and fat content indicating that fatter fish tend to be less feedefficient. However, the association between RFI and fat content was not constant over timeand was driven mostly by one replicate from one line. We also found positive correlationsbetween RFI and the total number of feed demands. Our findings highlight the interest ofusing fat content in selective breeding programs to improve feed efficiency and highlightedthe interest in exploring the relationship between feed efficiency and feeding behaviour in fis