Maslinic acid added to the diet increases growth and protein-turnover rates in the white muscle of rainbow trout (Oncorhynchus mykiss)

Maslinic acid (2-alpha, 3-beta-dihydroxiolean-12-en-28-oic acid) is a triterpenoid compound present in fruit and leaves of Olea europaea that can be used as an additive in the diet of trout. The present work investigates the effects of maslinic acid on growth, protein-turnover rates and nucleic acid concentration in trout white muscle. Five groups of 180 trout of a mean body mass of 20 g were fed for 225 days with diets containing 0, 1, 5, 25 and 250 mg of maslinic acid per kg of diet. At the end of the experiment, white-muscle weight and protein-accumulation rate of trout fed with maslinic acid were higher than in control. The total content of DNA, RNA, and protein in trout fed with 25 and 250 mg of maslinic acid kg(-1) were significantly higher than in control. The protein:DNA ratio was also slightly higher than control. In the same groups of trout, fractional (K(S)) and absolute (A(S)) protein-synthesis rates increased to more than 80% over the control values while no differences were found in the fractional protein-degradation rate (K(D)). These results, similar to previous findings in liver, show that maslinic acid can act as a growth factor when added to a standard trout diet.