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Title: Family differences related to carbohydrate utilization in rainbow trout Oncorhynchus mykiss

item Overturf, Kenneth - Ken
item Gaylord, Thomas
item Barrows, Frederic

Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2007
Publication Date: 2/9/2008
Citation: Overturf, K.E., Gaylord, T.G., Barrows, F. 2008. Family differences related to carbohydrate utilization in rainbow trout Oncorhynchus mykiss. Book of Abstracts World Aquaculture Society Feb 9-12 Orlando, Florida.

Interpretive Summary:

Technical Abstract: Rainbow trout utilize protein as an energy source much more efficiently than carbohydrates. Alternative diets utilizing plant material typically contain higher levels of carbohydrate than standard fish meal diets. The goal of this study was to determine if there are molecular and physiological differences between families reared on high and low carbohydrate diets. Two diets were formulated and used for this study that contained equal protein and fat levels and either 10% carbohydrate (low carb diet) or 38.5% carbohydrate levels (high carb diet). Wheat flour was the source of carbohydrate in the diets. Replicate groups of mixed families were fed the diet for 16 weeks. Six families were used to determine if genetic differences occur between families for carbohydrate utilization. Individuals were pit tagged so that individual growth data could be compared to other parameters among communally reared families. Average initial weight of starting fish for all families was 56 grams (std +11 grams), and as seen in figure 1, there was a significant difference in weight between groups according to the diet fed. This significant difference was noted for all families. Figure 2 shows that there was also a significant difference in feed conversion and specific growth rate seen for fish reared on the different diets. Weight gain, feed conversion ratios, protein retention efficiency, proximate analysis, degradation activity, plasma IGF and cortisol, and gene expression for a number of genes involved in the glycolytic and other metabolic related pathways were used to evaluate for differences in dietary utilization between the two diets and the six families of fish. Degradation enzymes evaluated included calpain, proteasome 20, and caspase 3 and 8. These same degradation genes were evaluated by quantitative PCR along with calpastatin, and several other related degradation genes. The genes pyruvate kinase, phosphoglucomutase, phosphoglycerate kinase, hexokinase, glucose 6-phosphatase, fructose 1,6- bisphosphatase, transaldolase, pyruvate dehydrogenase, glutamate dehydrogenase, and glutamine s-transferase were used to evaluate for expression to assay the metabolic effects of carbohydrate when incorporated at different levels in a rainbow trout diet. Final results will be reported at the meeting.