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The present experiment was conducted to determine the dietary total phosphorus requirement of juvenile yellow catfish Pelteobagrus fulvidraco. Six diets with increasing dietary phosphorus concentration (0.43, 0.55, 0.78, 0.90, 1.05 and 1.18% of dry matter, respectively) were fed to triplicate groups of 20 fish each (mean initial body weight, 2.68 ± 0.08 g, mean ± SD) to apparent satiation for 7 weeks. Weight gain and specific growth rate (SGR) increased with increasing dietary phosphorus level from 0.43 to 0.90% and then declined over dietary phosphorus level of 0.90% (P \ 0.05). Phosphorus retention increased with increasing dietary phosphorus level from 0.43 to 0.55% and then declined over dietary phosphorus level of 0.55% (P \ 0.05). Dietary phosphorus levels significantly influenced whole body crude protein and ash contents (P \ 0.05), but not whole body lipid content (P [ 0.05). Vertebrae phosphorus content increased with dietary phosphorus level from 0.43 to 0.78% (P \ 0.05) and then plateau over the level of 0.78% (P [ 0.05). Dietary phosphorus level significantly influenced condition factor, viscerosomatic index and hepatosomatic index (P \ 0.05). The relationship between SGR and whole body ash content against dietary phosphorus levels could be expressed as a second-order polynomial equation and the points of 0.89 and 0.85% were considered to be the optimal dietary total phosphorus level, respectively. Based on broken-line analysis of vertebrae phosphorus content, the minimal dietary total phosphorus requirements for maintaining maximum phosphorus storages were estimated to be 0.76% phosphorus.

The present experiment was conducted to investigate the e¡ects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow cat¢sh, Pelteobagrus fulvidraco. Nine diets were formulated to contain three protein levels (30%, 36% and 42%), each with three carbohydrate levels (24%, 30% and 36%). Each diet was randomly assigned to triplicate groups of 20 ¢sh (initial mean body weight: 8.24 AE 0.20 g) in indoor £ow^through ¢breglass tanks. The experiment continued for 8 weeks.Weight gain and speci¢c growth rate were similar for the ¢sh fed the 36% and 42% protein diets but higher than that fed the 30% protein diet. At the 36% protein level, carbohydrate contents varying from 24% to 36% (P/E ratio of 24.0^28.2 mg protein kJ À 1 ) had no sig-ni¢cant e¡ects on growth performance and feed utilization (P40.05). Protein e⁄ciency ratio tended to increase with dietary carbohydrate level at the same protein level. Dietary treatments signi¢cantly in£uenced body composition (Po0.05), but not the condition factor, viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio (P40.05). Based on these observations, 36% protein and 24^36% carbohydrate with the P/E ratio of 24.02 8.2 mg protein kJ À 1 seemed suitable for optimal growth and feed utilization, and carbohydrate could cause protein-sparing e¡ect in diets for juvenile yellow cat¢sh. E¡ects of dietary protein to carbohydrate ratios on yellow cat¢sh WJ Ye et al.Ã Values are means AE SD of three replicates and values with di¡erent letters within the same column are signi¢cantly di¡erent atPo0.05. wIBW (g ¢sh À 1 ), initial mean body weight. zFBW (g ¢sh À 1 ), ¢nal mean body weight. kFI (g ¢sh À 1 ): feed intake. ‰WG (weight gain, %) 5 (¢nal mean body weight À initial mean body weight)/initial mean body weight. zSGR (speci¢c growth rate, % day À 1 ) 5 100 Â (ln (¢nal mean body weight) À ln (initial mean body weight))/days. ÃÃ FCR (feed conversion rate) 5 g feed intake/(FBW À IBW).wwPER (protein e⁄ciency ratio) 5 g gain/g protein feed. Aquaculture Research, 2009, 40, 1410^1418 E¡ects of dietary protein to carbohydrate ratios on yellow cat¢sh WJ Ye et al. Ã Values are mean AE SD of three replicates and values with di¡erent letters within the same column are signi¢cantly di¡erent at Po0.05. E¡ects of dietary protein to carbohydrate ratios on yellow cat¢sh WJ Ye et al.

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