Effect Of Genetics And Feeding Strategies On Growth Of Rainbow Trout

To study the influence of genetics and feeding strategy, we measured growth and mRNA expression of protein degradation markers in growth‐selected and control rainbow trout that were either fed to satiation or limit‐fed. Fish were limit fed to 90–95% of the feed required to reach maximal growth. Length and weight of 1600 trout were measured every six weeks for 24 weeks. After 24 weeks of dietary treatment there was an interaction (p<0.05) between genetics and feeding strategy for both length and weight. The least squares means ± the standard error of the means for weight of satiation/control, limit‐fed/control, satiation/selected and limit‐fed/selected fish were 371 ± 6, 350 ± 4, 544 ± 24, and 426 ± 16 grams and for length 299 ± 2, 291 ± 2, 347 ± 2 and 330 ± 2 mm, respectively. mRNA expression of 4 components of the ubiquitin/proteasome machinery were decreased (p<0.05) by an average of 17% in muscle of the growth‐selected fish consistent with a reduced capacity to degrade protein. No effect of feeding strategy was seen for mRNA expression nor was an interaction detected. No differences in IGF‐1 concentrations were detected due to feeding strategy or genetics. This suggests decreased degradation of protein through proteasomes and caspases could be the cause for increased weight and length of the growth‐selected trout. Support: Aquaculture Product and Marketing Development Project.