Effect of Dietary Phosphorus on Growth and Its Excretion in Tiger Shrimp, Penaeus monodon

Six semi-purified diets were formulated with supplemented phosphorus levels of 0, 0.5, 1.0, 1.5, 2.0 and 2.5% at a fixed calcium level of 1.25% and the effect of dietary phosphorus on growth, FCR, body phosphorus and its excretion in shrimp Penaeus monodon was studied. The results of a 45 day feeding trial, in triplicate, on the juveniles of P. monodon (initial average live –weight 2.54 ±0.28g) had shown that phosphorus is indispensable in the diet and the best performance (147.3 and 154.5% increase in live-weight and 1.44 and 1.57 FCR) was recorded by the diet supplemented with 1.0 and 1.5% phosphorus which was significantly (P<0.05) higher than the performance of the other diets tested. Higher phosphorus supplementation suppressed growth and increased FCR. The shrimp maintained body phosphorus and calcium levels in a ratio of 1:3 irrespective of dietary levels of phosphorus. There was no significant change in the proximate composition of post feeding trial shrimp. Phosphorus excretion in faeces of P. monodon increased proportionately with dietary phosphorus while the excretion level far exceeded the body phosphorus level in the shrimp fed with diets having supplemented phosphorus level above 1.5%. Even the shrimp fed with 0% phosphorus diet had 0.10% phosphorus in their faeces. The phosphorus levels in shrimp feeds vis-a-vis its excretion into aquaculture environment have been discussed.