Response of juvenile abalone, Haliotis discus hannai, to dietary calcium, phosphorus and calcium/phosphorus ratio
2001
Tan, B. | Mai, K. | Liufu, Z.
The feeding experiment was conducted to determine the response of juvenile abalone, Haliotis discus hannai, to dietary calcium, phosphorus and the ratios of calcium to phosphorus. Fifteen isonitrogenous (approximately 30% CP) casein-gelatin-based diets containing five graded levels of phosphorus (0%, 0.5%, 1.0%, 1.5% and 2.0%) for each of three levels of calcium (0%, 1.0% and 2.0%) were fed to the animals previously fed a basal diet (0.23% total P and 0.17% total Ca) for 14 days. After 16 weeks of feeding, survival ranged from 94.7% to 100.0% with no significant difference among dietary treatments. The weight gain rate (WGR), daily increment in shell length (DISL), carcass concentrations of lipid and protein, soft-body alkaline phosphatase activity and phosphorus, zinc, manganese contents were significantly affected by dietary phosphorus levels. Supplementation of 1.0% and 2.0% calcium to the basal diet reduced soft-body phosphorus deposition and did not appear to increase the nutritive value of the diet, indicating that a dietary calcium supplement is not required under the present experimental conditions. The dietary phosphorus requirements were evaluated from the pooled WGR and DISL, respectively, by using the second-order polynomial regression analysis. On the basis of the pooled WGR and DISL, the optimum ranges of dietary available phosphorus were 0.65-1.17% (approximately 0.7-1.2% total P), and 0.64-1.14% (approximately 0.7-1.2% total P), respectively. Based on these results, about 1.15% available phosphorus (1.25% of total P) is recommended for the maximum growth of H. discus hannai, and if dietary available phosphorus is reduced from 1.15% to 0.65%, the growth of the abalone may be depressed with 5% likelihood. The calcium/phosphorus ratio of the diets is not important within the range assessed (approximately 0.1:1-9.0:1).
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