Abstract:
The effect of dietary levels of lecithin on growth, survival moulting, FCR and body phospholipid levels of early postlarval freshwater prawn macrobrachium rosen bergii was examined using semi-purified diets in a 56 day feeding experiment. Five casein-egg albumin based semi-purified diets incorporated with 0,2.5,5,7.5 and 10% of purified soy lecithin (60% phosphatidylcholine) were formulated and fed to prawns (ten numbers per treatment) with an initial mean weight of 0.05386g. In order to examine the influence of lecithin at different growth stages of postlarvae the assessment was made every fourteen days during the study period. The result showed that although the overall growth performance was not affected by dietary inclusion of lecithin, SGR% of the prawns fed with the diet containing 2.5% of lecithin showed a significant difference at P<0.01level during the first fourteen days of growth. Similarly the FCR also showed significant variation (P<0.01) between the diets tested in the first and second fortnights (14th and 28th day). In the first fortnight the diets (D1, D2 and D3) produced consistent FCR, while the diets supplemented with higher levels produced higher values. No significant differences (P<0.01) between treatments were detected with regard to survival rate, moulting frequency and body phospholipid levels of the prawns with the termination of the experiment. The prawns moulted once in every night days and no abnormalitied like exuvia entrapment were noticed in any of the experiment animals . Increment of body phospholipids with respect to levels of dietary lecithin suggests a possible replacement of body PL pool with that of dietary PL. The result of the study suggests that supplementation of lecithin at a level of 2.5% in the diet can accelerate growth and improve FCR during the early postlarval phase of Macrobrachium rosenbergii (ie, upto 4 weeks after larval settlement) beyond this, supplementation of lecithin is not needed in the diet. No other deficiency of excess symptoms was detected in the experimental prawns and it is found that lecithin is not responsible for Exuvia Entrapment Disease in Macrobrachium rosenbergii postlarvae.
