Toward the Genetic Improvement of Feed Conversion Efficiency in Fish

Abstract

Feed conversion efficiency (FCE) is the effectiveness with which feed is converted to saleable fish product. Feed costs are a major input to aquaculture production systems, and genetic improvement in FCE may therefore have an important influence on profitability. FCE is usually expressed by a composite measure that combines feed intake and growth rate. The two most common measures are feed conversion ratio (feed intake/weight gain over a specified time interval) and its inverse, feed efficiency. Feed conversion ratio and feed efficiency are measures of gross FCE, because they do not distinguish between the separate energy requirements of growth and maintenance. There is abundant evidence of substantial genetic variation in FCE and its component traits in terrestrial livestock species and, although data are few, the same is likely for cultured fish species. The major problems with selecting from this variation to genetically improve FCE in fish species are: It appears impractical to measure feed intake on individual fish, so that family mean data must be used. We do not know the optimal time period over which to test fish for FCE. We do not know the genetic correlations between FCE under apparent satiation or restricted intake conditions, or between FCE at different times in the production cycle. If these problems can be overcome, selection to improve FCE might be best achieved by measuring feed intake of growing animals, and by utilizing genetic correlations that are likely to exist between feed intake and other production traits to develop a weighted selection index.

Indicators of genetic variation for feed conversion efficiency in black bream

“…This is an important point because the high fecundity of most aquaculture species means that particular aquaculture enterprises usually specialize in specific parts of the production cycle. This is especially true for finfish species, where the proportion of growing animals to breeding animals is very high and FCE in the growing phase of the production cycle is more likely to be closely correlated with efficiency over the whole production system (Doupé & Lymbery 2003).…”

“…Physical marking of young fish is notoriously difficult (Doupé, Partridge & Lymbery 2003) and the most promising option for the future is genetic fingerprinting (Fishback, Danzmann, Ferguson & Gibson 2002). Nevertheless, even with a specific marking system there are still technical difficulties with measuring feed intake on individual fish (Doupé & Lymbery 2003). The alternative is to measure feed intake on a group basis, as in the current design, but with much greater replication.…”

“…There is substantial genetic variation in FCE and its component traits in terrestrial livestock species, and although data are few, the same is likely for cultured fish (Doupé & Lymbery 2003). There are, however, a number of problems with selecting from this variation to genetically improve FCE in fish species.…”

“…This means that for each species, we need an empirical determination of the optimal (i.e. most cost effective) test period to accurately estimate feed intake and weight gain (Doupé & Lymbery 2003).…”

Improving feed efficiency in fish using selective breeding: a review

“…() on beef cattle, RFI is defined as the difference between feed consumed by an animal and its predicted consumption estimated by a regression model taking into account the feed requirements for maintenance and growth as independent variables (Kennedy et al . ; Doupé & Lymbery ; Martins et al . ).…”