The interaction effect between methionine and L-carnitine on growth parameters, carcass composition and blood indices in rainbow trout Oncorhynchus mykiss

The main goal of the current study is to investigate the effects of L-carnitine supplement mixed with methionine on fat metabolism efficacy and consequently growth performance improvement in rainbow trout. In order to study the interaction effects between methionine and L-carnitine, three levels of methionine (0.5, 1 and 1.5%) and three levels of  L-carnitine (0.5, 1 and 1.5 g/kg) were added to a an experimental diet. This led to nine experimental diets. The results showed that growth parameters such as final weight, feed conversion rate and specific growth rate were influenced by addition methionine (p<0.05). However, L-carnitine supplementation did not change growth parameters in rainbow trout, except final weight (p>0.05). The result also revealed that  in general fish fed diets containing methionine and L-carnitine showed a better growth performance in comparison to control diet (without methionine and L-carnitine). Inclusion of both methionine and L-carnitine reduced blood glucose concentration compared with control diet (P< 0.05). Carcass protein level increase by addition of both methionine and L-carnitine compared to control diet (p< 0.05). Dislike to protein, administration of both methionine and L-carnitine reduced fat content of carcass compared to control diet (p< 0.05). In conclusion, administration of L-carnitine along with methionine at low level had a larger positive impact on growth and musscle composition in rainbow trout.