Effects of Different Levels of Probiotic Protexin on the Growth Indices and Survival in Grass Carp (ctenopharingodon idella) Fry

Application of probiotics as a way of growth in fish breeding is of a high potentiality. This study was conducted to evaluate the effect of probiotic protexin on the growth and survival of grass carp fry (ctenopharingodon idella). This experiment was conducted in a completely randomized design in four treatment and three replicates and 360 fry with average weight of 0.62±0.221 gr, (30 fry per aquarium) for 60 days. In treated group, Probiotic protexin was supplemented in aquaria water at three different levels of 1×10 5 , 2×10 5 and 3×10 5 cfu/ml every 4 days and the other three aquaria were added without any probiotic and treated as the control. The rate of feeding was on the base of the 5 percent of body weight for 3 times a day. All three experimental treatments showed significant increase (p<0.05) in final mean weight, weight gain percent, specific growth rate and feed coefficient efficiency with control treatment and among experimental treatments, The highest final mean weight (3.9±0.12), weight gain percent (520.7±13.01), specific growth rate (SGR) (3.0±0.04) and feed coefficient efficiency (79.6±3.16) were found in treatment received 3×105 cfu/ml. All three experimental treatments showed significant difference (p<0.05) in feed conversion ratio with control treatment and the best feed conversion ratio (1.2±0.04) was obtained in treatment received 3×105 cfu/ml. Also, maximum of survival percentage (100%) obtained in treatment of received 3×10 5 cfu/ml. The results indicated that the ability of probiotic protexin to influence the increase of growth performance and survival in grass carp fry is relatively high and the best effective doze is level of 3×10 5 cfu/ml.