Dietary mineral requirements of Penaeus vannamei : evaluation of the essentiality for thirteen minerals and the requirements for calcium, phosphorus, copper, iron, zinc, and selenium

Abstract

The dietary requirements for calcium, phosphorus, Ca:P ration, copper, iron, zinc and selenium as well as the effects of phytate on zinc bioavailability to juvenile P. vannamei were evaluated utilizing a casein/gelatin semi-purified diet. At the conclusion of a 33-day feeding trial a dietary requirement for calcium was not found; however, a significant interaction between calcium and phosphorus suggested that calcium decreased the bioavailability of phosphorus. In the absence of calcium supplementation, the basal diet containing 0.35% phosphorus was adequate to maintain normal growth and survival. In the presence of 1.0% and 2.0% supplemental calcium, the supplementation of 0.5 to 1.0% phosphorus and 1.0 and 2.0% phosphorus, respectively, was required to maintain normal growth. Shrimp fed diets supplemented with 3.0 and 4.0% calcium had reduced growth, regardless of phosphorus supplementation. At the conclusion of a 42-day feeding trial, a dietary copper requirement of 34 mg Cu/kg diet was determined. Dietary copper deficiency was characterized by poor growth and depressed copper concentrations in the hepatopancreas, carapace and hemolymph as well as enlargement of the heart. At the conclusion of the 35-day feeding trial, a dietary iron requirement was not demonstrated, indicating that the dietary iron requirement of shrimp was no higher than 12 mg Fe/kg which was present in the unsupplemented diet. This value is lower than requirement values reported for various fish species, and is presumably due to the presence of a copper-based respiratory pigment as opposed to an iron-based pigment. The lack of dietary zinc supplementation during a 35-day feeding trial did not affect growth and survival but depressed the zinc content of the hepatopancreas. Zinc concentrations of the hepatopancreas were maximized with the supplementation of 15 mg Zn/kg diet (33 mg total Zn/kg) or greater. The presence of phytate reduced the bioavailability of zinc and consequently zinc mineralization of the tissues. Thus, in the absence of phytate, shrimp feeds should contain 33 mg Zn/kg and in the presence of phytate approximately 200 mg Zn/kg diet. Supplementation of selenium resulted in a linear increase in weight gain during a 28-day feeding trial, indicating a dietary requirement of 0.2 to 0.4 mg Se/kg. Although, the dietary requirement for selenium was not confirmed in a second experiment, it appears to be similar to the requirements of fish (approximately 0.2 mg Se/kg diet).