Effects of dietary microbial levan on growth performance, RNA/DNA ratio and some physio-biochemical responses of Labeo rohita (Hamilton) juveniles

Six isonitrogenous and isocaloric semi-purified diets were prepared with different levels of microbial levan: control (Basal), T1 (Basal + 2.5gkg(-1) diet), T2 (Basal + 5gkg(-1) diet), T3 (Basal + 7.5gkg(-1) diet), T4 (Basal + 10gkg(-1) diet) and T5 (Basal + 12.5gkg(-1) diet), fed to six groups of fish in triplicate tanks. The results of the 60days feeding trail showed that supplementation of dietary levan significantly affected the weight gain percentage and specific growth rate of the treatment groups fed at 10gkg(-1) or more levan. Lowest feed conversion ratio (FCR) value and highest survival percentage among levan fed groups were observed with 12.5gkg(-1) incorporation (T5) and was comparable with (T4) group. Significant increase in muscle RNA level and RNA/DNA ratio was observed with the increasing dietary levan. Fish fed 12.5gkg(-1) levan had significantly higher protease, amylase and lipase activities compare with the control group. Lowest Aspartate aminotransferase (AST) activity in the liver and muscle was observed in the T5group fed with highest level of dietary levan. Overall results conclude that dietary microbial levan incorporation at 12.5gkg(-1) could be used as potent dietary prebiotic for the culture of L.rohita juveniles.