Effect of some Managerial and Environmental Factors on Fish Performance

A factorial design was conducted in order to study the effect of fish stocking density (10 and 20 fish/aquarium) and dietary probiotic treatments on growth performance, survival rate, feed utilization, blood components, chemical body composition, water quality parameters and disease resistance of Nile tilapia fish (Oreochromis niloticus with initial weight 1 g) after three weeks acclimation under normal laboratory conditions. The experimental period lasted 14 weeks after start during the period from June to September 2011. The obtained results could be sammarized as follows: 1-The live body weight, daily weight gain, specific growth rate, daily feed intake and feed conversion ratio of Nile tilapia fish were significantly (P<0.05 and 0.01) improved with decreasing fish stocking density, dietary probiotic supplementation with bacterial mixture (Lactobacillus acidophilus, Streptococcus thermophilus and bifidobacterium bifiduim). The interaction between the tested fish stocking density and dietary probiotic supplementation with bacterial mixture (Lactobacillus acidophilus, Streptococcus thermophilus and bifidobacterium bifiduim) was significant at most of the experimental periods studied. 2-The survival rate of Nile tilapia fish was insignificantly affected by fish stocking density, dietary probiotics supplementation and the interaction between fish stocking density and probiotic treatments at all experimental periods studied.