Effects of supplemental dietary L-carnitine on growth and body composition of beluga (Huso huso) Juveniles

The effect of feed supplemented with L-camitine at four levels of ۰, ۳۰۰, ۶۰۰ and ۹۰۰mg kg-۱ on growth performance and body composition of beluga, H. huso, juveniles was evaluate din two separate trials. In the first trial, ۱۸۰ juveniles (۵۲۵±۹gw) were fed with the test diet for a period of ۷۱ days, and the trial extended to another ۱۲۶ days in the second phase by randomly selecting ۱۲۰ juveniles (۸۷۰.۷±۳۲g) and rearing them with similar diets. All trials, in triplicates, were conducted in circular fiberglass tanks (۲۰۰cm diameter, ۴۰cm height).The fish were fed ۴ times daily to apparent satiation. In the first phase, L-carnitine did not significantly affect mean final weight, feed conversion ratio (FCR) or specific growth rate (SGR) of the fish, however, the fish receiving ۹۰۰mg kg-۱ L-carnation showed better growth increment, SGR and feed efficiency (FE) than those in control group (p³۰.۰۵); neither did it significantly affect protein, lipid, moisture or ash as well as leptosomatic index (HSI) (p³۰.۰۵). The protein efficiency ratio (PER) was significantly affected by L-carnitine supplemented diet, particularly at ۹۰۰mg kg-۱(p£۰.۰۵). In the second phase, fish fed L-carnitine-supplemented diets produced significantly higher W۲, SGR and PER than the control group (p£۰.۰۵), but HSI decreased significantly (P£۰.۰۵).At the end of the trial, the whole body composition of fish did not differ significantly among experimental treatments, but slightly reduced lipid content were observed at ۶۰۰ and ۹۰۰mg kg-۱ L-carnitine (p£۰.۰۵).The results of this study indicated that supplementation of diets with ۳۰۰-۶۰۰mg carnitine kg-۱ improved growth rate, feed utilization and stimulated protein-sparing effect in this species.