Effect of stocking density and probiotic dietary supplementation on growth performance, feed conversion and survival of postlarvae of the freshwater prawn (Macrobrachium rosenbergii)

The present study was conducted at the Fish Hatchery Saft Khalid, Behera Governorate, Egypt, for two months in order to investigate the effect of stocking density and probiotic (Ecobiol Aqua) dietary supplementation on growth performance, feed utilization, survival rate and whole body chemical composition of postlarvae of the freshwater prawn (Macrobrachium rosenbergii) of an initial weight 0.161g. reared in indoor nursery concrete tanks. A total number of 1350 postlarvae freshwater prawns were divided randomly into 18 concrete tanks (1 m^2 area each) to represent three stocking densities (50; 75 and 100 PL/m^2) with or without probiotic supplementation in three replicates each treatment. The experimental prawns were fed during the experimental period (8 weeks) on a diet contained 37.5% crude protein 5times/day at a rate related to the development stage. The treatments applied were D_1A; D_2A; D_3A; D_1B; D_2B and D_3B i.e. densities 50; 75 and 100 animals/m^2 without probiotic and densities 50; 75 and 100 animals/m^2 with supplemental probiotics, respectively. Results obtained are summarized in the following: 1- Water quality parameters tested were within the permissible levels recommended for optimum growth and development of freshwater prawn. 2- Both densities D_1 and D_2 (50 and 75animals/m^2) recorded significantly (p 0.05) higher final weights; total weight gains; specific and relative growth rates compared to the highest density, regardless of the probiotic effect. 3- Probiotic supplementation had insignificant effects on final weight; total weight gain; specific and relative growth rates, regardless of stocking density. 4- Within each stocking density supplementing the diets of freshwater prawn with probiotic improved the survival rate and the improvements were more pronounced at the lower stocking densities. 5- The best feed conversion ratio (FCR) (the lowest) was recorded by D_1A group (p 0.05) followed by D_2B; D_1B; D-2A; D_3B and D_3A, respectively. 6- Neither stocking density nor probiotic supplementation released any significant effects on whole body chemical composition of freshwater prawn. Based on the obtained results, the optimum stocking density of postlarvae M. rosenbergii laid between 50 to 75animals/m^2 and increasing the stocking density more than75/m^2 had negative effects on growth performance parameters. Also the results obtained may lead us to recommend the supplementation of probiotic (Ecobiol Aqua) to postlarvae M. rosenbergii diets in order to improve the survival rate during the nursery period.