Estimation of apparent phosphorus availability from inorganic phosphorus sources for Penaeus vannamei

Abstract

The determination of net phosphorus absorption (apparent phosphorus availability, APA) from various feedstuffs by shrimp and the leaching losses from feeds are required for the evaluation of nutrient sources in terms of their nutritional, economic and environmental impacts. Utilizing chromic oxide as an inert marker, APA for inorganic phosphorus sources and the effects of calcium supplements on APA were evaluated in Penaeus vannamei. Based on the results of the present study, the following APA values were determined: calcium phosphate monobasic, 46.3%; calcium phosphate dibasic, 19.1%; calcium phosphate tribasic, 9.9%; potassium phosphate monobasic, 68.1%; sodium phosphate monobasic, 68.2%. APA values for diets utilizing sodium phosphate monobasic as the phosphorus source were significantly depressed by the presence of calcium lactate (50.0% APA) but not by calcium carbonate (65.5% APA) or calcium chloride (68.2% APA). Although leaching losses for some of the test diets were high, APA values did not appear to be influenced by leaching. Total fecal phosphorus and dissolved reactive phosphorus leaching from the test diets varied with phosphorus and calcium source. Phosphorus losses from a commercial shrimp diet after immersion were considerably lower than values reported for commercial salmon diets. Decreased bioavailability of dietary phosphorus to shrimp and reduced leaching losses from the shrimp feed would indicate pollution loads will follow a pattern different from that of fish production systems.