Submitted to: Aquaculture Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/17/2004
Publication Date: 6/12/2005
Citation: Silverstein, J., Hostuttler, M.A., Blemings, K.P. 2005. Strain differences in feed efficiency measured as residual feed intake in rainbow trout. Aquaculture Research 36:704-711. Interpretive Summary: Improving the conversion of feed consumed into muscle, or feed efficiency, is an important objective for all meat animal industries including aquaculture. There are two important impacts of improved feed efficiency on sustainability. As feed efficiency improves, the amount and therefore cost of feed required for production decreases. Additionally, improved efficiency implies less loss of nutrients and other pollutants to the environment. In aquaculture, feed efficiency has typically been calculated as the weight gained by a fish divided by the weight of feed consumed. This paper examines a statistic called 'residual feed intake' which has been widely used in other agricultural animal species and offers some statistical advantages over traditional feed efficiency calculations. Six different cross-types were evaluated for differences in residual feed intake by testing 5 individuals from each cross-type for a total of 30 experimental animals. The relationships among growth feed intake and feed efficiency were also evaluated. Significant differences for feed efficiency were found between cross-types, and fish that ate more had better efficiency. Use of the residual feed intake methods should help identify animals with superior feed efficiency and offer improved statistical properties for use in calculating correlations with other traits.
Technical Abstract: The efficient use of feed for growth and meat production is important for all animal production industries including aquaculture. Residual feed intake (RFI) is an alternative measure of feed efficiency that has been widely used in livestock production. RFI was calculated as the difference between intake observed and intake predicted on the basis of a bioenergetics model; a low RFI indicates greater efficiency. RFI offers some advantages as a selection criterion for improving production efficiency over traditional feed efficiency statistics because it is not a ratio, and it typically has a larger coefficient of variation. The RFI of individually reared rainbow trout progeny from six different genetic cross-types was examined for genetic variation. Proximate analysis and nitrogen retention were also evaluated to determine if differences in RFI correlate to differences in body composition and nutrient retention and varied by cross-type. Differences between cross-types indicated a genetic component for RFI, with the most efficient fish of approximately 160g consuming 0.99g less and inefficient fish consuming 0.05g more feed per day than expected. Lower RFI was associated with higher growth rates (r=-0.38, P<0.05) and greater nitrogen retention (r=-0.82 P<0.001).