Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2005
Publication Date: 3/21/2006
Citation: Silverstein, J. 2006. Relationships among feed intake, feed efficiency and growth in juvenile rainbow trout (Oncorhynchus mykiss). North American Journal of Aquaculture.68:168-175. Interpretive Summary: While fast growth is a trait of primary importance for animal production, efficiency of production, or the efficiency with which feed is converted into flesh is also a trait of major concern. Feed costs can represent over 50% of the variable cost of animal production. There has been some work done that demonstrates variation in feed efficiency in fishes, however the feeding protocols have not been standardized and this has led to some confusion over the relationships among feed intake, growth and feed efficiency. In the experiments described here, individual fish were fed either as much as they could eat (to satiation) or a restricted ration, and the relationship between feed intake, growth and feed efficiency was evaluated under these conditions. It was found that when fish could eat to satiation, variation in efficiency was greater, and high consumption was related to poorer efficiency. When feed was moderately restricted the relationship between consumption and efficiency was much weaker. Greater variation in efficiency is seen by feeding to satiation. An additional important finding in this work was that fish from the same genetic groups reared individually or in social groups had a similar ranking for efficiency. This means that studies done on individually reared fish for experimental measurements are relevant to fish held in more typical production situations.
Technical Abstract: In fish the correlation between feed consumed and body weight gain is typically greater than 0.8. Individual differences in the efficiency of converting feed into body weight causes this correlation to be less than 1.0. Improving the efficiency of production is important for both economic and environmental sustainability. The purpose of this work was to define the relationships between feed intake, weight gain and feed efficiency (measured as residual feed intake) in rainbow trout fed either to apparent satiation or a fixed ration. The genetic variation for feed efficiency was also examined to determine whether sufficient genetic variation exists to selectively breed for increased feed efficiency. Results indicate that under an apparent satiation feeding regime a weak but significant correlation exists between weight gain and improved efficiency (r = -0.31, P < 0.04). Furthermore, significant genetic variation in residual feed intake was demonstrated. When fed a fixed ration, the correlation between weight gain and feed efficiency was stronger (r = -0.57, P < 0.001), but the genetic variation in feed efficiency was not significant. Estimates of feed efficiency measured on individuals from full-sib families and measured on groups of individuals from the same families were correlated (r = 0.66, P = 0.03), suggesting that feed efficiency measured on individually reared fish captures a trait expressed in social groups as well.