Calcium, phosphorus and magnesium requirements in the diet of shrimp Penaeus indicus

摘要

Calcium, phosphorus, and magnesium requirements in the diet of Indian white shrimp Penaeus indicus were studied using semi-purified diets. During a 45 day feeding trial, shrimps with an initial average length of 25 mm and weight of 0.15 g, showed significantly higher growth (p< 0.01) and low FCR (p< 0.05) when fed with diet containing 0.53% of calcium and 1.05% phosphorus. Higher levels of dietary calcium supressed growth and increased FCR, though survival was unaffected. Shrimps fed with a phosphorus deficient diet were sluggish and weak and levels of phosphorus exceeding 1.05% showed no beneficial effect. The body calcium of shrimps fed with diets containing different levels of calcium was lower than the initial value and decreased as dietary levels of calcium increased. The body phosphorus of shrimps on the other hand, increased as levels of dietary phosphorus was increased. A dietary Ca-P ratio of 1:1.98 gave the best growth and FCR for P. indicus, while the Ca-P ratio in shrimps showed a decreasing trend with dietary calcium. Addition of magnesium to the diet from 0.1 to 0.7% also supressed growth and increased FCR. The total ash content of shrimps decreased as levels of magnesium was increased; however, the magnesium level of shrimps remained practically constant. Results suggest that the magnesium requirement may be satisfied through absorption from the water.