Physiological changes in muscle of rainbow trout fed different ration levels

Abstract

The effects of different ration levels on muscle growth dynamics and activity of metabolically important enzymes in the muscle of rainbow trout ( Salmo gairdneri Rich.) were investigated in a study lasting from startfeeding throughout life. Three experimental ration levels, adequate feeding, moderate restriction and strong restriction, were defined according to expected growth. Groups of trout were maintained at constant experimental ration levels in order to study short-term or long-term effects, or subjected to changed levels to study compensatory effects. In this paper results from the first year of the ongoing experiment are presented. Somatic growth increased with increasing rations. No compensatory growth was observed in groups transferred from restricted to adequate feeding. Fiber area in white muscle was correlated with body weight, indicating a growth mechanism in white muscle based on fiber enlargement. This conclusion is further supported by fiber size distribution. In red muscle, fiber area had a strong correlation with ration level. Protein and water content were stable. Glycogen varied with changed ration level. The activity of phosphofructokinase in white muscle as well as 3-hydroxyacyl-CoA dehydrogenase, citrate synthetase and, to a lesser degree, cytochrome oxidase in red muscle changed with altered ration level.